ABSTRACT CAMPOS, ASHLEY. Effect of Therapeutic Florfenicol

ABSTRACT

CAMPOS, ASHLEY. Effect of Therapeutic Florfenicol Treatment of Steers on the Prevalence and Antimicrobial Resistance of Campylobacter and the Comparison of Campylobacter Strains with Different Antimicrobial Resistance Profiles in Cattle Feces (Under the direction of Dr. Sophia Kathariou).

Campylobacter is the leading causes of foodborne illness oftentimes linked to cattle. Infections are typically self-limiting; however, cases with prolonged symptomatology may require treatment with antibiotics, such as macrolides and fluoroquinolones. Antibiotics are used for a variety of different purposes ranging from therapeutic to preventive measures; overuse of these antibiotics in humans and animals may have exerted selective pressure leading to antibiotic- resistant microbes. Cattle are frequently treated with florfenicol for therapeutic and metaphylactic treatment of respiratory disease. In this study, six calves were administered florfenicol and fecal samples were subsequently collected pre- and post- florfenicol administration in two independent trials, up to 38- and -40- days post-treatment. Our objective was to study the effect of therapeutic florfenicol treatment of steers on the prevalence and antimicrobial resistance of Campylobacter. C. jejuni was the most common species isolated, followed by C. coli, and lastly, C. hyointestinalis. Majority of the isolates were pan-sensitive

(PS), while <30% were resistant to one or more antibiotics. A marked reduction of

Campylobacter-positive samples was seen between 24-96 h post treatment in both trials. While the minimum inhibitory concentrations (MIC) values of antibiotics tested remained relatively the same before and after treatment for pan-sensitive strains, the MICs for nalidixic acid and tetracycline increased 3-fold in Trial 1 and 2-fold in Trial 2, respectively. The MIC values for florfenicol remained between a range of 1-2 µl before and after treatment, averaging 1.6 µl. Antibiotic resistance in Campylobacter is often conferred by point mutations; point mutations in the gyrA gene confers high resistance to fluoroquinolones and point mutations in 23S rRNA confers high resistance to macrolides. Resistance to antibiotics typically confer a fitness cost to pathogens; however, resistance to fluoroquinolones confers a fitness advantage to C. jejuni.

Cattle have been implicated as a major reservoir and transmission vehicle for Campylobacter and potential dissemination of antibiotic-resistant strains. Our objective was to determine whether specific antibiotic resistance in Campylobacter confers a fitness advantage in cattle feces. Three isolates with different antibiotic resistance profiles pan-sensitive (PS) C. jejuni, tetracycline- and fluoroquinolone-resistant (TQ) C. jejuni, and nalidixic acid-resistant C. hyointestinalis) were selected and their survival in feces was measured over several time points at either 4ᵒC or 25ᵒC over 5 and 2 days, respectively. A pronounced difference in survival length between the temperatures was seen, with prolonged survival at 4ᵒC. Survival was similar between the two C. jejuni strains, while C. hyo had a lower survival throughout both temperatures. At 25ᵒC, both C. jejuni strains had similar log reduction, 0.56 for CJ TQ and 0.68 for CJ PS; however, a slight difference in the log reduction of the C. jejuni strains at 4ᵒC was seen, with a log reduction of

0.034 for CJ TQ and -0.06 for CJ PS. Although the C. hyo strain declined much slower (log reduction of 0.11) than the C. jejuni strains at 25ᵒC, it declined much faster at 4ᵒC (log reduction of 0.32).

All Rights Reserved Effect of Therapeutic Florfenicol Treatment of Steers on the Prevalence and Antimicrobial Resistance of Campylobacter and the Comparison of Campylobacter Strains with Different Antimicrobial Resistance Profiles in Cattle Feces

by Ashley Campos

A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Masters of Biochemistry

Biochemistry

Raleigh, North Carolina 2020

APPROVED BY:

______Sophia Kathariou Jonathon Olson Committee Co-Chair

______Robert Rose Driss Elhanafi Committee Co-Chair

______Derek Foster Michael Goshe

DEDICATION

To my parents, thank you for your eternal patience, support, and love. I could not have done it

without you.

BIOGRAPHY

Ashley Campos was born in San Jose, Costa Rica. She moved to the United States at the age of

2. Coming from an immigrant family, she learned the value of hard work from her parents. She carried that work ethic with her to college. She earned academic and sports scholarships and graduated with her bachelor’s degree in Biology from Queens University of Charlotte. After graduating, Ashley took a few years to explore the working life. She gained experience as a medical scribe, implementations specialist, and customer service representative. Ashley always strived to continue to grow her mind and push herself out of her comfort zone and so, she pursued a Masters in Biochemistry at NC State, where she would get experience in research.

After her time at NC State, Ashley continued to explore other opportunities in the biopharmaceutical world.

iii

TABLE OF CONTENTS

LIST OF TABLES ...... vi LIST OF FIGURES ...... vi Chapter 1: Literature Review- Campylobacter ...... 1 Campylobacter ...... 1 Antimicrobial Resistance (AMR) ...... 2 Bovine production ...... 4 Antibiotics used in bovine production ...... 6 Treatment of cattle & Observed impacts on Campylobacter and other pathogens ...... 8 References ...... 10 Chapter 2: Impact of florfenicol on prevalence and antimicrobial resistance of Campylobacter in cattle ...... 18 Abstract ...... 18 Introduction ...... 19 Methods ...... 21 Animals, treatments, and sample collection ...... 21 Campylobacter isolation ...... 22 AMR/MIC testing ...... 23 Results ...... 24 Florfenicol treatment was accompanied by pronounced but transient reduction of Campylobacter prevalence...... 24 Changes in AMR profiles could be noted post-treatment upon resumption of Campylobacter-positive status ...... 25 Treatment was not accompanied by changes in florfenicol MIC ...... 26 Discussion ...... 27 Tables/Figures ...... 33 References ...... 45 Chapter 3: Comparison of Campylobacter strains with different antimicrobial resistance profiles in cattle feces ...... 51 Abstract ...... 51 Introduction ...... 52 Methods ...... 54 Bacterial strain and growth media ...... 54 Cattle feces ...... 55 Assessment of Campylobacter survival in bovine feces ...... 55 Results ...... 56 Discussion ...... 57 Figures ...... 60 References ...... 62

LIST OF TABLES

Table 1-1 Sample collection employed in this study within two separate trials ...... 33

Table 1-2 Resistance and susceptibility breakpoints according to NARMS. [NARM]

National Antimicrobial Resistance Monitoring System. NARMS 2006

executive report ...... 34

Table 1-3 Average, range, and median MIC in µg/ml of the antibiotics tested for

pan-sensitive and resistant strains ...... 35

Table S1 Excel table of isolates collected in both trials (supplemental file will be available for

download directly beneath ETD PDF) ...... 66

LIST OF FIGURES

Figure 1-1 Schematic diagram of the administration of florfenicol in cattle ...... 37

Figure 2-1 Isolation and characterization of Campylobacter from bovine feces ...... 38

Figure 3-1 Prevalence of Campylobacter-positive samples in (A) Trial 1 and (B) Trial 2 ...... 41

Figure 3-2 Campylobacter species AMR profiles. (A) Trial 1 and (B) Trial 2 ...... 43

Figure 4-1 Survival of Campylobacter hyointestinalis and Campylobacter jejuni in

bovine feces ...... 60

Figure 4-2 Log reduction of Campylobacter hyointestinalis and Campylobacter jejuni in

bovine feces relative to inoculum ...... 61

CHAPTER 1: Literature Review of Campylobacter

CAMPYLOBACTER

Campylobacter is a gram-negative, zoonotic bacterium that has been described as spiral or

“curved rod.” They are between 0.2 to 0.9 microns wide and 0.5 to 5 microns long, have a low

G/C content, and are highly motile (Facciola et al., 2017). Optimal growth for Campylobacter spp. ranges from 37°C to 42°C, the typical temperature of poultry (Epps et al., 2013, Silva et al.,

2011). They prefer low oxygen or microaerobic environments and have been known to cause gastroenteritis, also known as campylobacteriosis, in humans. Campylobacteriosis is characterized by watery or bloody diarrhea, fever, and abdominal pain (Acheson et al., 2001,

Moore et al., 2005). Foodborne campylobacteriosis has been estimated to account for 845,024 illnesses, 8463 hospitalizations, and 76 deaths annually and one in every 1,000 cases lead to a serious condition called Guillain-Barre syndrome, which causes paralysis (CDC 2019). Although the mortality rate of Campylobacter infections is low, this foodborne illness has been a public health concern due to its high morbidity rates and increasing antimicrobial resistance.

C. jejuni and C. coli have been the spp. most associated with Campylobacter infections and the most common spp. found in cattle feces (Thomas et al., 2020). C. jejuni is a naturally competent species that is also highly mutable. One difference between the two species is C. jejuni’s ability to hydrolyze Hippurate; the enzyme hippuricase has been used to distinguish the two strains via

PCR (Silva et al., 2011). In earlier years, the impact and number of Campylobacter infections were underestimated and not recognized to be a cause of human enteritis until the mid-1970s; however, with advanced methods of detection, Campylobacter has been deemed a major cause of human illness (Moore et al., 2005). Despite the importance of Campylobacter in human

foodborne illnesses, few studies have been conducted to understand the effects of antibiotics on

Campylobacter in bovine feces.

Antimicrobial Resistance (AMR)

Campylobacteriosis is typically self-limiting; however, occasional use of antibiotics is required for prolonged symptomatology. Although fluoroquinolones or macrolides have been the most common antibiotics used (McCrackin 2016), tetracycline and gentamicin have also been used for therapeutic treatment of infections associated with Campylobacter (Silva et al., 2011, Lapierre et al., 2016). Aminoglycosides, including gentamicin, are typically used with systemic infections while tetracycline are used for more severe cases (Silva et al., 2011, Dai et al., 2020). Several studies have indicated concerns for increasing resistance to fluoroquinolones; thus, making macrolides the first-line treatment of campylobacteriosis. Fluoroquinolone-resistant

Campylobacter has been placed amongst the high priority pathogens against which new antibiotics are needed (Dai et al., 2020, Tacconelli et al., 2018).

Out of the CDC laboratory-confirmed Campylobacter isolates, 49% were resistant to tetracyclines, 22% were resistant to quinolones, and 2% were resistant to macrolides (CDC

2019). The populations at highest risks are the young, the elderly, and the immunocompromised with an overall mortality rate of 0.24% of culture-confirmed cases (Dai et al., 2020, Yang et al.,

2020). Overuse of antibiotics in both humans and livestock has led to an increase in antibiotic resistant Campylobacter spp. (Yang et al., 2019, Sproston et al., 2018, Silva et al., 2011, Bennani et al., 2019). In a study by Inglis et al., their results indicated that antimicrobial administration of antibiotics typically used in beef production in North America, such as chlortetracycline, sulfamethazine, monensin, tylosin, and virginiamycin, may indeed select for antimicrobial

resistant Campylobacter in cattle (Inglis et al., 2005). Other studies have shown correlation between administration of antibiotics during production in poultry and selection for resistant bacteria (Smith et al., 2000). These antibiotic-resistant strains can complicate treatment of infections, leading to prolonged illness, increased mortality and co-morbidity rates, and increased hospitals costs (Silva et al., 2011, Lapierre et al., 2016, CDC 2019). The increased trend of antimicrobial resistance has become a forefront public health problem.

Several genetic mechanisms are associated with the dissemination of antimicrobial resistance in

Campylobacter spp. Tetracycline, kanamycin, and chloramphenicol resistance have been reported to be plasmid-mediated while resistance to fluoroquinolones, such as ciprofloxacin and nalidixic acid, or macrolides, such as erythromycin, are chromosomal (Moore et al., 2005,

McCrackin 2016). Resistance to tetracycline in Campylobacter is conferred by mutations in the tet(O) gene commonly found in plasmids and can be horizontally transferred to other bacteria.

Resistance to fluoroquinolones and macrolides are due to mutations to DNA gyrase (gyrA genes) and 23S rRNA, respectively (Alfredson and Korolik 2007, Wei and Kang 2018, Engberg et al.,

2001, Wieczorek and Osek 2013).

The most commonly identified antimicrobial resistance in Campylobacter isolates in cattle feces has been resistance to tetracyclines, with records showing 38% prevalence in feedlot cattle in

Alberta, Canada to 68% in beef and 73% in dairy cattle in the U.S. (McCrackin 2016). Although quinolones use in poultry in the U.S. was discontinued in 2005, according to the 2015 NARMS

Retail Meat Annual Report, resistance to ciprofloxacin and nalidixic acid in C. jejuni strains has continued to increase and remain high in cattle and chicken (NARMS 2017). Resistance to

ciprofloxacin isolated from fecal samples of beef cattle has increased from 14.0% in 2013 to

20.4% in 2015 (NARMS 2017). Studies have shown that simply removing antibiotics, particularly fluoroquinolones and macrolides, from the food animal production does not guarantee elimination of antimicrobial-resistant Campylobacter (McCrackin et al., 2016, Luo et al., 2005). Although mutations that allow resistance to macrolides are detrimental to C. jejuni, the same cannot be said of resistance to fluoroquinolones. Fluoroquinolones resistance confer a fitness advantage to Campylobacter strains; removal of these antibiotics from the environment has not been linked to reduction to quinolone-resistant phenotypes (Yang et al., 2019).

Some studies have shown C. coli have been more likely to acquire antibiotic resistance than C. jejuni (Tang et al., 2017, Silva et al., 2011, Bae et al., 2005). Specifically, C. coli isolates have been shown to acquire resistance to macrolides, particularly erythromycin, more readily than C. jejuni isolates (Engberg et al., 2001, Alfredson and Korolik 2007).

BOVINE PRODUCTION

Campylobacter is common to livestock and has several routes of transmission, such as direct contact, consumption of raw or unpasteurized milk, and through produce and water contamination (Acheson et al., 2001, Wesley et al., 2000). As discussed above, although poultry has been the primary reservoir of Campylobacter and linked to most cases of campylobacteriosis, cattle have also been implicated in these infections (Lapierre et al., 2016, Moore et al., 2005,

Silva et al., 2011). Campylobacter spp., including C. jejuni and C. coli, are often shed in cattle feces, posing a serious concern for human infection (Stanley and Jones 2003). Prevalence of

Campylobacter in fecal samples from cattle has been reported to be significant, approximately

37-55%; however, predominant species found varies among reports (McCrackin 2016, Moore et

al., 2005). Campylobacter jejuni prevalence in cattle has been shown to range between 0.8% to

100% depending on several factors (Bailey et al., 2003). Prevalence of Campylobacter in bovine feces has been linked to age, seasonal temperature, and diet (Sinton et al., 2007, Stanley and

Jones 2003). Campylobacter prevalence has been shown to be higher in warmer seasons compared to colder seasons (Sato et al., 2004). Younger calves are colonized more frequently and subsequently shed Campylobacter more frequently than older cattle; Campylobacter prevalence of calves up to 6 months old has been shown to be 10 to 100 times higher than those of adult animals (Stanley and Jones 2003). Feedlot cattle are colonized more frequently (12-

92%) than pasture beef cattle (0-52%) or dairy cattle (0-24%) (Bailey et al., 2003, McCrackin

2016). Feedlot cattle and grazing cattle differ in their diet and lifestyle as feedlot cattle often have controlled watering and feeding facilities for the sole purpose of beef production while grazing cattle graze freely on the grass (Meat & Livestock Australia 2012).

Studies have shown increased C. jejuni prevalence in dairy cattle when access to C. jejuni contaminated surface waters compared to access to controlled chlorinated water (Hannien et al.,

1998). Diet, feeding regimens, dietary supplements, and use of probiotics have been shown to play a major factor in colonization of Campylobacter in cattle (Wesley et al., 2000). Diet can alter gut homeostasis and potentially influence colonization of Campylobacter and the differences in feeding between feedlot and grazing cattle may account for the differences in

Campylobacter prevalence. Feedlot diet include higher percentage of carbohydrates compared to pasture diet, which may provide a more suitable environment in the gastrointestinal tract for

Campylobacter to survive and proliferate (Bailey et al., 2003).

ANTIBIOTICS USED IN BOVINE PRODUCTION

Data on the consumption of red meats, poultry, fish, and shellfish was collected for the year 2001 and per capita consumption was measured in pounds per capita per year. Beef, chicken, and pork were qualitatively ranked as the highest. Beef had a per capita consumption of 62.9, followed by chicken with a per capita consumption of 53.9, and lastly followed by pork with 46.7. Fish, shellfish, and turkey were qualitatively ranked as medium and lamb, mutton, and veal were qualitatively labeled as low (USFDA 2003). This apparent high consumption of beef, chicken, and pork suggests high concern for potential bacterial contamination. Data from national surveys conducted between 1992-1997 were collected representing the prevalence and subsequently qualitative ranking of Campylobacter contamination of different animal-derived foods. Poultry was ranked highest with 60-90% prevalence of Campylobacter contamination, followed by pork with 32% prevalence. Beef was considered to have the lowest prevalence of Campylobacter contamination with 0-4% prevalence (USFDA 2003).

Antibiotics are administered for a variety of purposes, including for growth promotion, metaphylactic, prophylactic, and therapeutic purposes (Landers et al., 2012). In a 2015 summary report of antibiotics sold or distributed in food producing animals, tetracyclines and ionophores were shown to be the most commonly used antimicrobials in animals with 44% and 33% use, respectively (FDA 2016). In 2015, the Food and Drug Administration (FDA) changed the antibiotic use policy in relation to livestock production. Prior to this policy change, many

“medically important” antibiotics, i.e., antibiotics used in human medicine, were used as growth promoters. Following this policy change, these “medically important” antibiotics can no longer be used as growth promoters but can be used for disease prevention and treatment. Additionally,

this policy change also requires that “medically important” antibiotics is under the direct supervision of a licensed veterinarian (USFDA 2009).

Ionophores, used for growth promotion, and chlortetracycline, used for control and treatment of respiratory disease, were the antibiotics most used in the feeds of cattle feedlots, approximately

40% of all feedlots (USDA 2019). In 2016, 87.5% of feedlots in the U.S. were giving antimicrobials in feed, water, or by injection for prevention, control, and treatment of disease, or growth promotion (USDA 2019). Once a group of animals in the population is diagnosed with an infection/clinical disease, the whole population may be treated with antibiotics with the intention of preventing the spread of the infection to the other animals in close proximity, also known as metaphylaxis; approximately 59.3% of feedlots use metaphylaxis (Aarestrup 2014). Smaller feedlots (capacity of 1,000 to 7,999 head) have been shown to have a higher chance of being treated for metaphylactic purposes for prevention of shipping fever (92.6%) than larger feedlots

(capacity of 8,000 or more head) (45.0%) (USDA 2011). Antibiotics are also used in low concentration for growth promotion and prophylaxis. Antibiotics, such as sulfonamides, streptomycin, tetracycline, and penicillin were shown to have positive effects on increasing rate of weight gain or improved feed efficiency and were subsequently used in growth promotion

(USDA 2019). Several routes of administration of antimicrobials are used for livestock, including through the feed on a continuous basis for prophylaxis, metaphylaxis, and growth- promotion purposes (Palma et al., 2020).

TREATMENT OF CATTLE & OBSERVED IMPACTS ON CAMPYLOBACTER AND

OTHER PATHOGENS

In most animal hosts, Campylobacter exists as an intestinal commensal bacterium without causing clinical diseases; however, on occasion these bacteria may induce infections that lead to reproductive losses, such as abortions and infertility (Dai et al., 2020). Tetracycline is often used to control these reproductive diseases and treatment with tetracycline has been linked to the frequently found tetracycline-resistant bacteria (Inglis et al., 2005). Bovine respiratory disease

(BRD) is a serious disease that has caused high morbidity and mortality in feedlot cattle.

Fluoroquinolone antibiotics are also frequently used in veterinary medicine for treatment and control of infectious diseases of companion and food-producing animals (Giguere et al., 2013).

For example, enrofloxacin and danofloxacin are approved as an injectable solution for the treatment and control of respiratory disease of cattle in the U.S. and many other countries. They are also used for metaphylactic purposes to control BRD in beef and non-lactating dairy cattle at high risks of developing BRD. Approximately 43% of the feedlots included in the Feedlot 2011

NAHMS study reported therapeutic use of fluoroquinolones in approximately 42% of cattle with respiratory disease (USDA 2015). Substantial increase in the prevalence of fluoroquinolone resistance in Campylobacter isolates from cattle in the U.S. coincides with expanded use of fluoroquinolone antibiotics in cattle production (Tang et al., 2017).

Florfenicol is a time-dependent, broad-spectrum bacteriostatic antibiotic that is active against many gram-negative and gram-positive bacteria (Papich 2016). It is one of the most common antimicrobial drugs used to treat against respiratory pathogens, such as Actinobacillus pleuropneumoniae, Bordetella bronchiseptica, Mannheimia haemolytica, Pasteurella multocida,

and Streptococcus suis (Coetzee et al., 2019, Waldner et al., 2019). Its mechanism of action stems from irreversibly binding to the 50S ribosomal subunit, essentially preventing protein synthesis (White et al., 2000, Wei et al., 2016). Florfenicol’s mode of action resembles that of chloramphenicol; however, it does not carry adverse side effects and risks typically associated with use of chloramphenicol (Papich 2013, Davis and Papich 2014). Although the risks associated with florfenicol is significantly lower than chloramphenicol, it has been shown that florfenicol can select for cross-resistance with chloramphenicol among bacterial pathogens

(White et al., 2000). Its use has been limited to only cattle and swine in food-producing animals

(Kehrenberg et al., 2004). Elimination of florfenicol is prolonged (18 h) after IM injection, and

27 h after 40 mg/kg subcutaneously (Papich 2016, Lobell et al 1994).

REFERENCES

1. Landers T, Cohen B, Wittum T, and Larson E. A review of antibiotics use in food

animals: perspective, policy, and potential. 2012. Public Health Rep. 127(1); 4-22.

10.1177/003335491212700103

2. Palma E, Tilocca B, and Roncada R. Antimicrobial resistance in Veterinary medicine: An

overview. 2020. International Journal of Molecular Sciences. 21, 1914.

10.3390/ijms21061914

3. Dai L, Sahin O, Grover M, and Zhang Q. 2020. New and alternative strategies for the

prevention, control, and treatment of antibiotic-resistant Campylobacter. Translational

Research. https://doi.org/10.1016/j.trsl.2020.04.009

4. Tacconelli E, Carrara E, Savoldi A, Harbarth S, Mendelson M, Monnet DL, et al.

Discovery, research, and development of new antibiotics: the WHO priority list of

antibiotic-resistant bacteria and tuberculosis. Lancet Infect Dis. 2018;18(3):318–27.

https://doi.org/10.1016/S1473-3099(17)30753-3

5. Silva J, Leite D, Fernandes M, Mena C, Gibbs P, and Teixeira P. Campylobacter spp. as

a foodborne pathogen: a review. 2011. Front Microbiol.

https://doi.org/10.3389/fmicb.2011.00200

6. Thomas K, de Glanville W, Barker G, Benschop J, Buza J, Cleaveland S, Davis M,

French N, Mmbaga B, Prinsen G, Swai E, Zadoks R, and Crump J. Prevalence of

Campylobacter and Salmonella in African food animals and meat: A systematic review

and meta-analysis. 2020. Int J Food Microbiol. 315:108382.

https://doi.org/10.1016/j.ijfoodmicro.2019.108382

7. USDA. USDA Feedlot 2011 “Part IV: Health and Health Management on U.S. Feedlots

with a Capacity of 1,000 or More Head. USDA-APHIS-VS-CEAH-NAHMS. Fort

Collins, CO. #638.0913 (2015).

8. Giguere, S., Prescott, J. F., Baggot, J. D., Walker, R. D. and Dowling, P. M.

Antimicrobial Therapy in Veterinary Medicine. 2013. John Wiley & Sons, Inc, Ames, IA.

9. Stanley K and Jones K. Cattle and sheep farms as reservoirs of Campylobacter. 2003.

Journal of Applied Microbiology. 94, 104S-113S.

file:///C:/Users/ashle/Downloads/j.1365-2672.94.s1.12.x.pdf

10. Wesley I, Wells S, Harmon K, Green A, Schroeder-Tucker L, Glover M, and Siddique I.

Fecal Shedding of Campylobacter and Arcobacter spp. in Dairy Cattle. 2000. Applied

and Environmental Microbiology. 66(5); 1994-2000. 0099-2240/00/$04.0010

11. Bae W, Kaya K, Hancock D, Call D, Park Y, and Besser T. Prevalence and antimicrobial

resistance of thermophilic Campylobacter spp. from cattle farms in Washington State.

2005. Applied and Environmental Microbiology. 7(1); 169-174. 10.1128/AEM.71.1.169–

174.2005

12. Bailey G, Vanselow B, Hornitzky M, Hum S, Eamens G, Gill P, Walker K, Cronin J. A

study of the foodborne pathogens: Campylobacter, Listeria and Yersinia, in faeces from

slaughter-age cattle and sheep in Australia. 2003. 27(2); 249-257. Communicable

Diseases Intelligence Quarterly Report. http://www.cda.gov.au/

13. McCrackin M, Helke K, Galloway A, Poole A, Salgado C, and Marriott B. Effect of

antimicrobial use in agricultural animals on drug-resistant foodborne campylobacteriosis

in humans: a systematic literature review. 2016. Critical Reviews in Food Science and

Nutrition. 56:2115-2132. 10.1080/10408398.2015.1119798

14. USDA. Antimicrobial use and stewardship on US feedlots, 2017. 2019

https://www.aphis.usda.gov/animal_health/nahms/amr/downloads/amu-feedlots_1.pdf

15. Moore J Corcoran D, Dooley J, Fanning S, Lucey B, Matsuda M, McDowell D, Megraud

F, Millar C, Mahony R, Riordan L, O’Rourke M, Raw J, Rooney P, Sails A, and Whyte

P. Campylobacter. 2005. Vet. Res. 36; 351-382. 10.1051/vetres:2005012

16. Facciola A, Riso R, Avventuroso E, Visalli G, Delia S, and Lagana P. Campylobacter:

from microbiology to prevention. J Prev Med Hyg. 2017. 58(2): E79-E92.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5584092/

17. Epps S., Harvey R., Hume M., Phillips T., Anderson R., and Nisbet D. Foodborne

Campylobacter: Infections, Metabolism, Pathogenesis and Reservoirs. 2013.

International Journal of Environmental Research and Public Health. 10, 6292-6304.

10.3390/ijerph10126292.

18. Acheson D. and Allos B. Campylobacter jejuni Infections: Update on Emerging Issues

and Trends. 2001. Clinical Infectious Diseases. 32(8); 1201-1206.

https://doi.org/10.1086/319760

19. Lapierre L., Arias M., and Fernandez H. Antimicrobial Resistance in Campylobacter spp.

2016. Campylobacter spp. and Related Organisms in Poultry. Editors: Fonseca B,

Fernandez H, and Rossi D. 165-183. I 10.1007/978-3-319-29907-5_10

20. Inglis G, McAllister T, Busz H, Yanke L, Morck D, Olson M, Read R. Effects of

Subtherapeutic Administration of Antimicrobial Agents to Beef Cattle on the Prevalence

of Antimicrobial Resistance in Campylobacter jejuni and Campylobacter hyointestinalis.

2005. Applied and Environmental Microbiology. 71: 3872-3881.

10.1128/AEM.71.7.3872–3881.2005

21. Yang Y, Feye K, Shi Z, Pavlidis H, Kogut M, Ashworth A, and Ricke S. A historical

review on antibiotic resistance of foodborne Campylobacter. 2019. Front. Microbiol.

https://doi.org/10.3389/fmicb.2019.01509

22. Wieczorek K and Osek J. Antimicrobial resistance mechanisms among Campylobacter.

2013. BioMed Research International. https://doi.org/10.1155/2013/340605

23. Sato K, Bartlett P. Kaneene J, and Downes F. Comparison of prevalence and

antimicrobial susceptibilities of Campylobacter spp. isolates from organic and

conventional dairy herds in Wisconsin. 2004. Applied and Environmental Microbiology.

70 (3); 1442-1447. 10.1128/AEM.70.3.1442–1447.2004

24. Tang Y, Sahin O, Pavlovic N, LeJeune J, Carlson J, Wu Z, Dai L, Zhang Q. Rising

fluoroquinolone resistance in Campylobacter isolated from feedlot cattle in the United

States. 2017. Sci Rep. 7:494. 10.1038/s41598-017-00584-z

25. Alfredson D and Korolik V. 2007. Antibiotic resistance and resistance mechanisms in

Campylobacter jejuni and Campylobacter coli. FEMS Microbiol Lett. 277: 123-132.

10.1111/j.1574-6968.2007.00935.x

26. Coetzee J, Magstadt D, Sidhu P, Follett L, Schuler A, Krull A, Cooper V, Engelken T,

Kleinheiz M, and O’Connor A. Association between antimicrobial drug class for

treatment and retreatment of bovine respiratory disease (BRD) and frequency of resistant

BRD pathogen isolation from veterinary diagnostic laboratory samples. 2019. PLoS One.

14(12): e0219104

27. Waldner C, Parker S, Gow S, Wilson D, Campbell J. Antimicrobial usage in western

Canadian cow-calf herds. 2019. Can Vet J. 60(3): 255-267.

28. United States Food and Drug Administration [USFDA]. 2003. Guidance for Industry

(GFI) #152: Evaluating the Safety of Antimicrobial New Animal Drugs with Regard to

Their Microbiological Effects on Bacteria of Human Health Concern. Available

at: http://www.fda.gov/downloads/AnimalVeterinary/GuidanceComplianceEnforcement/

GuidanceforIndustry/ucm052519.pdf

29. United States Food and Drug Administration [USFDA]. 2009. Guidance for Industry

(GFI) #209: The Judicious Use of Medically Important Antimicrobial Drugs in Food-

Producing Animals. Available

at: http://www.fda.gov/downloads/AnimalVeterinary/GuidanceComplianceEnforcement/

GuidanceforIndustry/UCM216936.pdf.

30. United States Food and Drug Administration [USFDA]. 2015. Guidance for Industry

(GFI) #213: New Animal Drugs and New Animal Drug Combination Products

Administered in or on Medicated Feed or Drinking Water of Food- Producing Animals:

Recommendations for Drug Sponsors for Voluntarily Aligning Product Use Conditions

with GFI #209. Available

at: http://www.fda.gov/downloads/AnimalVeterinary/GuidanceComplianceEnforcement/

GuidanceforIndustry/UCM299624.pdf.

31. FDA. 2015 Summary Report on Antimicrobials Sold or Distributed for Use in Food-

Producing Animals. 2016. https://www.fda.gov/files/about%20fda/published/2015-

Summary-Report-on-Antimicrobials-Sold-or-Distributed-for-Use-in-Food-Producing-

Animals.pdf

32. Wei B and Kang M. Molecular Basis of Macrolide Resistance in Campylobacter Strains

Isolated from Poultry in South Korea. 2018. Biomed Res Int. 4526576.

10.1155/2018/4526576

33. Engber J, Aarestrup F, Taylor D, Gerner-Smidt G, Nachamkin I. Quinolone and

macrolide resistance in Campylobacter jejuni and C. coli: resistance mechanisms and

trends in human isolates. 2001. Emerg Infect Dis. 7(1); 24-34. 10.3201/eid0701.010104.

34. CDC. Campylobacter (Campylobacteriosis). 2019. CDC.

https://www.cdc.gov/campylobacter/index.html

35. Sproston E, Wimalaranthna H, and Sheppard S. Trends in fluoroquinolone resistance in

Campylobacter. 2018. Microb Genom. 4(8): e000198. 10.1099/mgen.0.000198

36. Bennani H, Mateus A, Hasler B, and Stark K. Overview of evidence of antimicrobial use

and antimicrobial resistance in the food chain. 2019. Royal Veterinary College.

https://piru.ac.uk/assets/files/App%206%20Overview%20of%20evidence%20of%20anti

microbial%20use%20and%20AMR%20in%20the%20food%20chain%20(Bennani%20et

%20al)%20December%202019.pdf

37. Smith, K. E., J. B. Bender, and M. T. Osterholm. Antimicrobial resistance in animals and

relevance to human infections, p. 483-495. 2000. In I. Nachamkin and M. J. Blaser

(ed.), Campylobacter, 2nd ed. American Society for Microbiology, Washington, D.C

38. NARMS. The National Antimicrobial Resistance Monitoring System: NARMS

Integrated Report, 2015. 2017. U.S. Department of Health and Human Services, FDA.

https://www.fda.gov/media/108304/download

39. Luo N, Pereira S, Sahin O, Lin J, Huang S, Michel L, and Zhang Q. Enhanced in vivo

fitness of fluoroquinolone-resistant Campylobacter jejuni in the absence of antibiotic

selection pressure (2005). Proc Natl. Acad. Sci. 102(3): 541-546.

10.1073/pnas.0408966102

40. Meat & Livestock Australia. National Guidelines for Beef Cattle Feedlots in Australia.

2012. Meat & Livestock Australia.

file:///C:/Users/ashle/Downloads/B.FLT.0338_B.FLT.0355_B.FLT.0431_3rd_Edition.pd

41. Papich M 2013. Antibiotic treatment of resistant infections in small animals. Vet Clin

Small Anim. 43’ 1091-1107. http://dx.doi.org/10.1016/j.cvsm.2013.04.006

42. Kehrenberg C. Mumme J, Wallmann J, Versphl J, Tegeler R, Kuhn T, Schwarz S.

Monitoring of florfenicol susceptibility among bovine and porcine respiratory tract

pathogens collected in Germany during the years 2002 and 2003. Journal of

Antimicrobial Chemotherapy. 54(2); 572-574. https://doi.org/10.1093/jac/dkh371

43. Papich M. Florfenicol. Saunders Handbook of Veterinary Drugs (Fourth Edition): Small

and Large Animals. 2017. Can Vet J. 327-329. https://doi.org/10.1016/B978-0-323-

24485-5.00264-3.

44. Davis J and Papich M. Antimicrobial Therapy. 2014. Equine Infectious Diseases (Second

edition). 571-584. https://doi.org/10.1016/B978-1-4557-0891-8.00065-8.

45. Hanninen M, Niskanen M, and Korhonen L. Water as a reservoir for Campylobacter

jejuni infection in cows studied by serotyping and pulsed-field gel electrophoresis

(PFGE). 1998. J. Vet. Med. 45; 37-42.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1439-

0450.1998.tb00764.x?casa_token=5sYr9SraNYsAAAAA:dMOJA5xmDwe7mgyIG9aB

X6gKAMW7OZ7NmQrLgiuKD3yqmtIUMcdu2SA4d9ZnPldOtinhegu5SydRcg

46. White D., Hudson C., Mauer J., Ayers S., Zhao S., Lee M., Bolton L., Foley T.,

Sherwood J. Characterization of Chloramphenicol and Florfenicol Resistance in

Escherichia coli associated with Bovine Diarrhea. 2000. J Clin Microbiol. 38(12): 4593-

4598. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC87642/pdf/jm004593.pdf

47. Wei C., Shien J., Chang S., Chou C. Florfenicol as a modulator enhancing antimicrobial

activity: example using combination with thiamphenicol against Pasteurella mulitocida.

2016. Front Microbiol. 7:389. 10.3389/fmicb.2016.00389

CHAPTER 2: Impact of florfenicol on prevalence and antimicrobial resistance of

Campylobacter in cattle

ABSTRACT

Campylobacter jejuni and Campylobacter coli are leading causes of foodborne illness, with cattle as a source. Antibiotic overuse in humans and animals may have exerted selective pressure leading to antibiotic-resistant microbes. Cattle are frequently treated with florfenicol for therapeutic and metaphylactic treatment of respiratory disease. Our objective was to study the effect of therapeutic florfenicol treatment of steers on the prevalence and antimicrobial resistance of Campylobacter, respectively. Campylobacter isolates (n=232) were characterized for species and resistance to a panel of antibiotics. Approximately 72% of isolates were pan-sensitive C. jejuni, followed by C. jejuni with resistance to both tetracycline and fluoroquinolone

(TQ;~23%). The latter were only encountered post-treatment in Trial 1. C. coli with resistance to both tetracycline and streptomycin (TS) was only encountered on day 28 post treatment in Trial

2. Nalidixic acid resistant C. hyointestinalis were also encountered, albeit infrequently (≤6%). A marked reduction of Campylobacter-positive samples was seen between 24-96 h post treatment in both trials. A subset of isolates was tested for minimum inhibitory concentration (MIC) to ciprofloxacin, tetracycline, nalidixic acid, and streptomycin, and florfenicol. While the MIC values of antibiotics tested remained relatively stable before and after treatment for pan-sensitive strains, the MICs for nalidixic acid and tetracycline increased 3-fold in Trial 1 and 2-fold in Trial

2, respectively. The MIC values for florfenicol remained between a range of 1-2 µl before and after treatment, averaging 1.6 µl. Understanding the prevalence and antimicrobial resistance of

Campylobacter in cattle in response to florfenicol treatment can increase our knowledge of

Campylobacter in the farm ecosystem and potentially lead to enhanced intervention strategies.

INTRODUCTION

Campylobacter is the leading zoonotic organism for human foodborne illness. It is common to livestock and has several routes of transmission to humans, such as direct contact, consumption of raw or unpasteurized milk, and through produce and water contamination (Acheson et al.,

2001, Wesley et al., 2000). Although poultry has been the primary reservoir of Campylobacter and linked to most cases of campylobacteriosis, cattle have also been implicated in these infections (Lapierre et al., 2016, Moore et al., 2005). Campylobacter spp., including C. jejuni and

C. coli, are often shed in cattle feces, and may contribute to the high prevalence of campylobacteriosis especially in or around farm areas. (Wesley et al., 2000, Tang et al., 2017,

Bae et al., 2005, Lapierre et al., 2016). The incidence of Campylobacter infection has increased in the U.S., affecting millions of citizens, and leading to increased direct medical costs every year (CDC, Foodnet).

Although campylobacteriosis is a self-limited infection, occasional use of antibiotics is required for prolonged symptomology; fluoroquinolones or macrolides have been the most common antibiotics used (McCrackin 2016, Alfredson and Korolik 2009). Resistance to fluoroquinolones is caused by a spontaneous point mutation in gyrA, which reduces the affinity of the fluoroquinolone for its target, the essential bacterial enzymes DNA gyrase, lessening its effectiveness and therefore- contributing to the increasing frequency of Campylobacter resistance to fluoroquinolones, especially resistance to ciprofloxacin (Yang et al., 2019). Drug- resistant Campylobacter is listed as a serious threat by the CDC and the increasing trend of antimicrobial resistance has become a forefront public health problem.

Increases in antibiotic-resistant Campylobacter may be connected to overuse of antibiotics in both clinical and agricultural environments (Yang et al., 2019, Sproston et al 2018). Antibiotics are widely used in the cattle industry for a variety of metaphylactic, prophylactic, and therapeutic purposes; however, most often, these approaches are used concurrently. For example, approximately one sixth of all lactating dairy cows receive therapeutic antibiotics for treatment of mastitis and one sixth of all beef calves entering feedlots in the U.S receive therapeutic antibiotics for treatment of respiratory disease. These populations also receive prophylactic antibiotic doses to prevent and control future mastitis and anticipated outbreaks of respiratory disease (Landers et al., 2012, Holman et al., 2019). Additionally, many healthy livestock populations in close vicinity of animals showing clinical symptoms are also treated with antibiotics to prevent spread of infection, also known as metaphylactic treatment (Aarestrup

2014, Ball et al., 2019).

Bovine Respiratory Disease (BRD) is a major disease that affects cattle leading to a significant economic cost to the beef industry. Several antimicrobials are used to control and treat BRD and other respiratory diseases in cattle. Florfenicol is a time-dependent bacteriostatic antibiotic that is a derivative of thiamphenicol. It is one of the most common antimicrobial drugs used to treat respiratory diseases (Coetzee, et al., 2019, Waldner et al., 2019).

Despite the importance of Campylobacter in human foodborne illnesses, few studies have been conducted to understand the impact of therapeutic drug exposure of cattle to Campylobacter prevalence, species, and antimicrobial resistance (AMR) profiles. In one study by Inglis et al., subtherapeutic administration of tetracycline to feedlot cattle, alone and in combination with

sulfamethazine, indeed appeared to select for Campylobacter resistant to tetracycline and some limited resistance to erythromycin, ampicillin, and ciprofloxacin (Inglis et al., 2005). A major objective of the current study was to determine the prevalence of Campylobacter in steers and estimate how the antimicrobial resistance of Campylobacter may be affected by florfenicol treatment of the animals. To address this objective, two trials were completed, six calves were administered florfenicol in each trial, and Campylobacter prevalence and AMR were monitored over 912-960 h (38-40 D) post-treatment.

METHODS

Animals, treatments, and sample collection

Two trials were completed over 912 (38 D) and 960 h (40 D), respectively. Trial 1 started on

5/20/2019 and ended on 6/29/2019, while Trial 2 began approximately one week later 7/05/2019 and ended on 8/19/2019. In each trial, six steers 5-6 months of age with a weight of 153-251 kg were given two different doses of florfenicol (Figure 1-1). All animals came from the same farm and were removed from their farm of origin to an indoor facility at NC State Veterinary school.

In each trial, three steers were injected subcutaneously once with a high dose of florfenicol

(40mg/kg), while the other three were injected intramuscularly twice with a low dose of florfenicol (20mg/kg), once at 0 h (first dose) and once at 48 h (second dose). One steer from each treatment group was housed together with one steer from the other treatment group to avoid animal-to-animal variation in gut microbiome community as described (D. Foster personal communication). The steers were housed in pairs in separate stalls and isolated from all other animals during duration of the study.

In Trial 1, pre-treatment (pre-T) samples were taken at 48 h and 24 h prior to treatment, as well as immediately prior to administration of the antibiotic (time 0 h), with a total of 18 fecal samples in the pre-T group. During the post-treatment (post-T) period, fecal samples were taken every 12 h between 12 h and 96 h, with a total of 36 samples, with additional samples collected at subsequent time points, up to 912 h (38 D) post-T, with a total of 16 post-T samples (Table 1-

1). In Trial 2, fecal samples labeled as Pre-T were taken at “pre 0 h” and 0 h, with a total of 12 fecal samples collected. Post-treatment samples were collected at the same time as in Trial 1 with the exception that the last sample was collected at 960 h (40 D) post-T (Table 1).

All cattle were housed in the same barn, and under the same care and management conditions.

Approximately 150g of fecal material was collected from the rectum of each steer by using a gloved hand and the samples placed in separate prelabeled sterile bags. All samples were placed in coolers on ice, transported to the laboratory and stored at 4ᵒC until processing, typically within

2-24 h.

Campylobacter isolation

Campylobacter was isolated by selective enrichment as described (Ghasrst et al., 2006). At each time point, the six samples were homogenized into a composite and 0.1g of the composite was placed into two 2-mL tubes of Bolton broth with supplements and lysed horse blood (Figure 2A).

Thus, at each time point, two separate subsamples from the composited material were processed in parallel. The two enrichment tubes were incubated in anaerobic jars containing Campy

GasPaks (Becton, Dickinson and Co.) at 37ᵒC for 24 h. Following the 24 h incubation, 150 µL of the suspension was serially diluted in Mueller Hinton Broth (MHB) (Becton, Dickinson and Co.) and 50 µl of appropriate dilutions (0, 10-2, 10-4) were spread-plated on modified charcoal-

cefoperazone agar (mCCDA) with the corresponding supplement (Oxoid, Ogdensburg, NY) and incubated microaerobically at 42ᵒC for 48 h (Figure 2B). Following 48h incubation, 3-4 positive colonies per sample were purified on Mueller Hinton Agar (MHA) (Becton, Dickinson and Co.) agar and incubated at 42ᵒC for 24 h (Figure 2C). Colonies were then characterized for species identification via PCR with hip and ceu primers for C. jejuni and C. coli, respectively, and preserved at -80ᵒC in brain heart infusion broth with 20% sterile glycerol, as described (Smith et al 2004). Non-C. jejuni and non-C. Coli isolates were tested for C. fetus targeting 23S rRNA via

PCR. One unknown isolate was sent off for sequencing and confirmed to be C. hyointestinalis.

The detection limit (in CFU/g) for Campylobacter used in this method is based on the assumption that if there was one CFU in the sample analyzed, we would get a positive culture by enrichment.

AMR/MIC testing

Isolates were tested as described (Good et al., 2019) for susceptibility to a panel of antibiotics, tetracycline (T), streptomycin (S), erythromycin (E), kanamycin (K), gentamicin (G) and the

(fluoro)quinolones, nalidixic acid and ciprofloxacin (Q) (Figure 2C). A subset of isolates was tested for susceptibility to chloramphenicol (Cm). The pan-sensitive strain C. jejuni ATCC

33560 was included as quality control in each test. A panel of isolates from both trials was tested for minimum inhibitory concentrations (MICs) to florfenicol, ciprofloxacin, tetracycline, nalidixic acid, and streptomycin. MIC testing strips were obtained from Liofilchem (Waltham,

MA) and MIC testing was done as per vendor recommendations. According to NARMS, the resistance breakpoints for florfenicol, ciprofloxacin, tetracycline, and nalidixic acid were ≥8

µg/ml, ≥1 µg/ml, ≥2 µg/ml, ≥32 µg, respectively (NARMS 2006). The resistance breakpoint for

streptomycin was ≥32 µg/ml, as described (Heuer et al 2008) (Table 2). The concentrations of nalidixic acid, tetracycline, and florfenicol, in the MIC strips ranged from 0.064-256 µg/ml, except for ciprofloxacin (.002-32 µg/ml) and streptomycin (0.064-1024 µg/ml). The plates were incubated at 42°C for 48 h under microaerobic conditions and the MIC was defined as the lowest concentration of an antimicrobial agent that inhibited growth on the plates.

RESULTS

Florfenicol treatment was accompanied by pronounced but transient reduction of

Campylobacter prevalence

Two subsamples were collected per time point, leading to 32 and 30 analyzed samples in Trial 1 and Trial 2, respectively. Approximately 61.3% (n=38/62) of those subsamples were positive for

Campylobacter (isolates from this study are listed in Table S1 which will be available for download directly beneath ETD PDF). In Trial 1, all fecal samples were positive before treatment and for the first 24 h after treatment. However, starting at 36 h post-treatment and until the 96 h timepoint, a significant drop in positive Campylobacter-positive samples was noted

(Fig. 3). Campylobacter could be recovered again after 96 h, with all samples remaining positive until the last time point at 912 h (38 D) (Fig. 3). Similar trends were noted in Trial 2, with marked reduction in Campylobacter-positive samples between 24 h and 96 h and Campylobacter recovery resuming thereafter (Fig. 3).

Changes in AMR profiles could be noted post-treatment upon resumption of

Campylobacter-positive status

The majority (12/15, 80%) of the pre-T isolates in Trial 1were pan-sensitive (PS) C. jejuni except for 0 h, for which all 3 isolates were resistant to nalidixic acid (NalR) and were putative C. hyointestinalis. C. hyointestinalis was not encountered after treatment. One putative C. hyointestinalis isolate was sent off for sequencing and confirmed to be C. hyointestinalis; therefore, we concluded the other 2 isolates in the same timepoint with similar antimicrobial resistance profiles were putative C. hyointestinalis. All 22 pre-T isolates in Trial 2 were PS C. jejuni. Immediately after treatment (12-36 h), all isolates in both trials (20 isolates in Trial 1 and

19 in Trial 2) were PS C. jejuni. However, upon resumption of Campylobacter-positive samples in Trial 1, and starting at 144 h post-T, the proportion of PS isolates was reduced while isolates with resistance to tetracycline, nalidixic acid, and ciprofloxacin (TQ) constituted the majority, accounting for 63% and 60% of the isolates at 120-168 h and at 336-912 h (14-38D) (Fig. 4). All pre-T isolates in Trial 2 were PS C. jejuni. Upon resumption of Campylobacter-positive samples, the isolates were again PS C. jejuni for the first 504 h (21 D). However, C. coli resistant to both tetracycline and streptomycin (TS) appeared suddenly in Trial 2 at 672 h (28 D). TS C. coli was only encountered at this single time point, with all isolates in the last timepoint at 960 h (40 D) being PS C. jejuni (Fig. 4). Testing of 11 C. jejuni isolates (5 from Trial 1 and 6 from Trial 2) for resistance to chloramphenicol failed to identify any that were resistant to this antibiotic. TS C. coli (one tested isolate) also lacked resistance to this antibiotic.

Treatment was not accompanied by changes in florfenicol MIC

Susceptibility to florfenicol was assessed by MIC testing of 16 isolates in Trial 1 (3 pre-T and 13 post-T) and 11 (2 pre-T and 9 post-T) isolates in Trial 2. Of these tested isolates, 7 isolates (4 in

Trial 1 and 3 in Trial 2) were tested for chloramphenicol resistance. In addition, ciprofloxacin, tetracycline, nalidixic acid, and streptomycin MIC was tested for selected isolates, including 13 in Trial 1 and 7 in Trial 2. In Trial 1, the average MIC values for ciprofloxacin, tetracycline, and florfenicol were similar before and after treatment for pan-sensitive strains, but the average nalidixic acid MIC increased 3-fold post-T (Table 3). In Trial 2, concurrently, the average MIC values for ciprofloxacin, nalidixic, and florfenicol were similar before and after treatment for pan-sensitive strains, while the average tetracycline MIC increased 2-fold after treatment. The

MICs for the C. jejuni PS isolates consistently remained below the threshold for resistance in both trials. As anticipated, the tetracycline MICs for C. jejuni TQ and C. coli TS strains encountered post-T were high (between 24-64 µg/ml and >256 µg/ml, respectively). Of the five

C. jejuni TQ isolates tested for MIC to tetracycline in Trial 1, one had a MIC of 24 µg/ml, two had a MIC of 48 µg/ml, and one had a MIC of 64 µg/ml. (Table S1). Similarly, streptomycin

MIC for C. coli TS isolates were >128 µg/ml (Table 3). In agreement with their designation as fluoroquinolone resistant, ciprofloxacin and nalidixic acid MIC values for C. jejuni TQ isolates ranged between 6-8 µg/ml and >256 µg/ml, respectively. The tetracycline, nalidixic acid, and ciprofloxacin MIC results of one of the TQ tested isolates gave inconsistent results. Florfenicol

MICs remained similar pre- and post-treatment, with a range between 1-2 µg/ml and averaging

1.6 µg/ml in both trials (Table 3 and Table S1).

DISCUSSION

Significant reduction in Campylobacter positive samples was noted between 36-96 h in Trial 1 and between 24-96 h in Trial 2. Knowing the pharmacokinetics of florfenicol, this would fit with when you would expect peak drug concentrations to be found in these steers. Elimination of florfenicol is prolonged (18 h) after IM injection, and 27 h after 40 mg/kg subcutaneously

(Papich 2016, Lobell et al., 1994). Gut lumen half-life is not known.

The overall prevalence of Campylobacter spp. in fecal samples of apparently healthy cattle was

64.5% (n=40/62). This is almost twice as high as findings in other similar studies reported on the prevalence level of Campylobacter spp. in cattle from different countries, including Malaysia

(33%) (Premarathne et al., 2017), Japan (39.6%) (Haruna et al., 2013), and Chile (35.9%)

(Fernandez and Hitschfeld 2009). Studies in the U.S. found only 19.2% Campylobacter prevalence levels in samples collected from feedlot, mature cows, and bulls (Sanad et al., 2011).

However, other studies have showed different prevalence of Campylobacter in the U.S.; Sato et al., isolated Campylobacter from 27.9% of the fecal samples collected in dairy herds; while

Gharst et al., reported Campylobacter recovery of 23.4% from feces of mature cattle at slaughter

(Sato et al., 2004, Gharst et al., 2006). This apparent difference in our values could be due to the low sample size in this study and overall design of the study. Although 40/62 pooled samples were positive, only one animal at each time point may have been positive. Combining/pooling the samples together may have attributed to the high prevalence. Additionally, the differences in the prevalence of cattle-associated Campylobacter can also be associated with other factors, including but not limited to, animal type (dairy versus feedlot), age, seasonal variations, geographic location, and methods of isolation.

C. jejuni was the most frequent (94.3%) species in the current study, followed by C. coli (4.3%) and C. hyointestinalis (2%). The latter was resistant only to nalidixic acid and briefly seen only in pre-treatment samples from Trial 1. This is congruent with many studies, showing a preferred prevalence of C. jejuni over C. coli in cattle (Karama et al., 2020, Premarathne et al., 2017, Cha et al., 2017, Kashoma et al., 2015). The percentage of C. jejuni versus C. coli differs from study to study possibly due to differences in farming practices, geographic locations, farm location and proximity to other livestock such as poultry. Additionally, season has been shown to affect C. jejuni prevalence in cattle, with higher peaks in warmer months (Cha et al., 2017, Grove-White et al., 2010). Since sampling occurred during the summer, it is possible the higher temperatures contributed to the high prevalence of C. jejuni. Additionally, by using a higher temperature, we are preferentially recovering C. jejuni and C. coli as C. fetus grows better at 37°C.

Antimicrobial resistance profiling revealed that 28.4% (66/232) of Campylobacter isolates were resistant to one or more antimicrobial agents. Multidrug resistance (resistance to two or more antimicrobial classes) was recorded in 27% (63/232) of isolates, including C. jejuni TQ and C. coli TS, encountered exclusively post-T in Trial 1 and Trial 2, respectively. This is congruent with several studies showing similar proportions of multi-resistant Campylobacter isolates recovered from cattle fecal samples (Karama et al., 2020, McCrackin 2016). The antimicrobial resistance in the study of Englen et al. showed 60% were resistant to one or more antimicrobials, while 19.6% were resistant to two or more antimicrobials (Englen et al., 2005). This apparent discrepancy may be due to the number of antimicrobials tested. Our study tested against 8 antibiotics while Englen et al. tested against 12 antibiotics. Of the 28.4% drug resistant

Campylobacter isolates, 27% shared resistance to tetracycline. This is lower than the studies of

Sanad et al. in which 47.7% and 49.1% of C. jejuni isolated from dairy and feedlot cattle,

respectively, were resistant to tetracycline (Sanad et al., 2011). Englen et al. also showed similar resistance levels to tetracycline in dairy (47.4%) and feedlot cattle (49.1%) (Englen et al., 2006,

Englen et al., 2005).

An estimated 22.8% of the C. jejuni isolates, all encountered from trial post-T, were ciprofloxacin- and nalidixic acid- resistant. Sanad et al. reported similar prevalence of ciprofloxacin-resistant C. jejuni strains (23.7%) (Sanad et al., 2011). However, Englen et al. found nalidixic acid and ciprofloxacin resistance at much lower prevalence among C. jejuni from feedlot cattle; at 10.2% and 1.8%, respectively (Englen et al., 2005). Campylobacter coli was only detected at one time point in the current study, and all the isolates were resistant to both tetracycline and streptomycin. Significantly higher prevalence of resistance to tetracycline

(65.7%) was reported by others (Englen et al., 2005). The resistance of nalidixic acid observed in these studies is intriguing, as this antimicrobial is not used clinically on cattle. Tetracyclines are the most common medically important antimicrobial used in cattle and are used for prevention, control, and therapeutic treatment; therefore, it is concerning to see the percentage of isolates resistant to tetracycline in the trials. Administration of florfenicol may have changed the dynamics of the microbiota of the steers leading to the original pan-sensitive strain to appear after Campylobacter presence resumed and later allowing the TQ strain to become more noticeable in the late stages. Resistance to tetracycline is found on the plasmid while resistance to nalidixic acid is caused by a point mutation. These two different antibiotic resistance profiles indicate two events must be happening to get resistance to TQ. Generally, one would not expect to get multidrug resistance on a plasmid. However, once drug concentrations get below minimum inhibitory concentration (after 96 h), it may be putting stress on the Campylobacter

organisms, perhaps leading to an SOS response that increases their mutations frequency, possibly increasing their competency.

Resistance against ciprofloxacin is of clinical significance because this antimicrobial is used to treat human campylobacteriosis. Studies in the U.S. have indicated rising fluoroquinolone resistance in Campylobacter, specifically to ciprofloxacin (Tang et al., 2017, Yang et al., 2019).

A study in Southwestern Alberta, Canada have shown an increasing resistance to ciprofloxacin since 2004 with a peak resistance rate of 30% in 2016 (Inglis et al., 2020). The observed lack of resistance to erythromycin, gentamicin, and kanamycin was not surprising. Prevalence of resistance to macrolides is approximately 10,000-fold lower than that of fluoroquinolone resistance (Yang et al., 2019, Wieczorek and Osek 2013). This can explain why we did not see resistance to erythromycin and potentially confirms macrolides as the treatment of choice for campylobacteriosis in the U.S as these Campylobacter isolates would be susceptible to this drug.

Susceptibility to florfenicol was assessed by MIC testing of 27 isolates (16 in Trial 1 and 11 in

Trial 2); of those 27 isolates, only 7 isolates (4 in Trial 1 and 3 in Trial 2) were tested for chloramphenicol resistance. Florfenicol MIC was below threshold (averaging 1.6 µg/ml) and no isolates were found to be chloramphenicol resistant. No difference in florfenicol MIC was found between pre- or post-treatment, ranging between 1-2 µg/ml. Despite potential selective pressure by florfenicol administration, no resistance to chloramphenicol was seen in either study.

Although chloramphenicol was banned in the U.S. many years ago, florfenicol is still often used for treatment of respiratory disease in feedlot cattle (Coetzee, et al., 2019, Waldner et al., 2019).

Resistance to chloramphenicol in Campylobacter typically confers cross-resistance to florfenicol by specific resistance genes, such as floR (Ma et al., 2004), and none of the tested isolates were

chloramphenicol- or florfenicol-resistant. Co-selection of resistance when florfenicol is used has never been addressed very well. One of the unfortunate byproducts of administration of antibiotics is co-selection. One would expect selection for florfenicol resistant strains, along with resistance to nalidixic acid or a different antibiotic. However, although the MIC of florfenicol did not change, nonetheless we still selected for resistant isolates. Perhaps, combining/pooling samples together may have influenced the findings of this study as perhaps only one steer could have been harboring this resistant isolate.

Overall, the MIC values of antibiotics tested for both trials stayed relatively the same before and after treatment for pan-sensitive strains, except that the nalidixic acid MIC increased 3-fold in

Trial 1 and tetracycline MIC increased 2-fold in Trial 2. Resistance to fluoroquinolones is the result of a single point mutation in the gyrA gene and evidence has shown mutation frequency to fluoroquinolone resistance is high (Yan et al., 2006, Yang et al., 2019). Appearance of random mutations may have been selectively pressured by the presence of florfenicol. As time passed in the post-treatment group, these nalidixic acid resistant mutants may have continued to multiply, thus increasing the MIC 3-fold. This is also indicative of the fact we started seeing frequent appearance of C. jejuni TQ isolates in the late post-T period in Trial 1. Resistance to tetracycline is conferred by the tet(O) gene frequently located on plasmids and in the presence of antimicrobial selection, conjugation plays a major role in the transfer of this plasmid-mediated resistance (Wieczorek and Osek 2013). The high prevalence of conjugative tet(O) plasmids and the selective pressure of antimicrobials may have contributed to the high number of tetracycline resistant isolates found in these trials and potentially explain the 2-fold increase in MIC of tetracycline in PS C. jejuni isolates post-T in Trial 2. The 2-fold and 3-fold increase in MIC of nalidixic acid and tetracycline, respectively, indicates there must be other mechanisms at play,

for example antimicrobial pumps may be one. Nonspecific mechanisms may be upregulated in response to stress. Some examples may include CME, Campylobacter multidrug resistant pump.

To determine if different mechanisms are at play, sequencing the different strains and comparing known sequences of C. jejuni could prove beneficial. This would help identify if the strain seen in this study has a known resistance mutation that may be associated with an efflux pump or some other antibiotic resistance mechanism. Other than sequencing, gel electrophoresis or PCR digestion profiles could be used to differentiate between strains.

Of note, the one isolate in trial 1 with the phenotype TQ was based on the standard tests (MHA growth at 32 ug/ml Nal and MHA growth at 1ug/ml Cip) but could not be confirmed with the strips. MIC testing of this TQ isolate provided confusing data, with values below the resistance threshold according to NARMS resistance breakpoints. Testing showed resistance to tetracycline and ciprofloxacin, but sensitivity to nalidixic acid; upon retesting of the TQ isolate, results showed sensitivity to ciprofloxacin, but resistance to nalidixic acid. The reasons behind these contradictory results are currently unknown; more testing will need to be completed to confirm.

TABLES/FIGURES

Table 1-1. Sample collection employed in this study within two separate trials

Time related to Trial 1 (samples, isolates) Trial 2 (samples, isolates)

treatment

Pre-Treatment -2d, -1d, 0 h P Pre 0 h, 0 h

(2, 6), (2, 6), (2, 3) (2, 12), (2, 10)

Post-Treatment 12-24h 12-36h

(3, 20) (3, 19)

120-168h, samples each 24 h 120-170h, samples each 24 h

(5, 30) (6, 36)

14 d-28 d, samples each 7 d 14-28d, samples each 7 d

(6, 44) (4, 28)

38 d 40 d

(2, 12) (1, 6)

Total (22, 121) (18, 111)

Table 1-2. Resistance and susceptibility breakpoints according to NARMS. [NARMS] National

Antimicrobial Resistance Monitoring System. NARMS 2006 executive report. Laurel, MD: U.S.

Department of Health and Human Services, 2006.

Antimicrobial Tentative Tentative MIC MIC MIC

Agent breakpoint breakpoint range range for range for

(µg/ml) for (µg/ml) for (µg/ml) PS resistant

resistance of susceptibility isolates isolates

Campylobacter of (µg/ml) (µg/ml)

spp. Campylobacter

spp.

Ciprofloxacin ≥1 ≤0.5 0.002-32 0.064-.25 6-8

Tetracycline ≥2 ≤1 0.016-256 0.047-.25 24-256

Nalidixic acid ≥32 ≤16 0.016-256 2-16 0-64

Florfenicol ≥8 ≤4 0.016-256 1-2 1.5-2

Streptomycin ≥32 ≤16 2-128 N/A >128

Table 1-3. Average, range, and median minimum inhibitory concentration (MIC) in µg/ml of the antibiotics tested for pan-sensitive and resistant strains

Trial 1 Ciprofloxacin Tetracycline Nalidixic Florfenicol Streptomycin

average average acid average average

(range; (range; average (range; (range;

median) median) (range; median) median)

(µg/ml) (µg/ml) median) (µg/ml) (µg/ml)

(µg/ml)

PS C. .094 .19 2 1.5 (.75-2;1)

jejuni

pre-T

PS C. .088 (.032- .15 (.047-.25; 6.25 (1.5- 1.65 (1.5-

jejuni .125; .079) .125) 12; 4.5) 2;1.5)

post-T

TQ C. 6.8 (6-8; 7) 46 (24-64; >256 1.7 (1.5-

jejuni 48) 2;1.5)

post-T

Table 1-3 (Continued).

Trial 2 Ciprofloxacin Tetracycline Nalidixic Florfenicol Streptomycin

average average acid average average

(range; (range; average (range; (range;

median) median) (range; median) median)

(µg/ml) (µg/ml) median) (µg/ml) (µg/ml)

(µg/ml)

PS C. .16 (.064-.25; .094 7 (6-8; 7) 1.5 (1.5-

jejuni .157) 2;1.75)

pre-T

PS C. .13 (.094-.19; .19 (.125-.25; 6.25 (2- 1.6 (1-3;1.5)

jejuni .125) 0.19) 16; 3.5)

post-T

TS C. coli >256 1.5 >128

post-T

Figure 1-1. Schematic diagram of the administration of florfenicol in cattle. Six steers 5-6 months of age with a weight of 153-251 kg were given two different doses of florfenicol. Three steers were injected subcutaneously once with a high dose of florfenicol (40mg/kg), while the other three were injected intramuscularly twice with a low dose of florfenicol (20mg/kg), once at

0 h and once at 48 h. One steer from each treatment group was housed together with one steer from the other treatment group.

Figure 2-1. Isolation and characterization of Campylobacter from bovine feces. 150g of feces

were collected from six different calves. Approximately 3g per feces were homogenized into a

composite and 0.1g of the composite was placed into two 2-mL tubes of Bolton broth with

supplements and lysed horse blood. At each time point, two separate subsamples from the composited material were processed in parallel and the two enrichment tubes were incubated in

anaerobic jars containing Campy GasPaks at 37ᵒC for 24 h (A). Approximately 150 µl of

overnight cultures were serially diluted into Mueller Hinton Broth (MHB) to 10-4 and 50 µl of appropriate dilutions (0, 10-2, 10-4) were spread-plated on modified charcoal-cefoperazone agar

(mCCDA) with the corresponding supplement and incubated microaerobically at 42ᵒC for 48 h

(B). Following 48h incubation, 3-4 positive colonies per sample were purified on Mueller Hinton

Agar (MHA) agar and incubated at 42ᵒC for 24 h. Colonies were then characterized for species

identification via PCR with hip and ceu primers for C. jejuni and C. coli, respectively. Non-C. jejuni and non-C. Coli isolates were tested for C. fetus targeting 23S rRNA. Colonies were also

tested against eight antibiotics, chloramphenicol, tetracycline, streptomycin, nalidixic acid, gentamicin, ciprofloxacin, erythromycin, and kanamycin. Colonies were later preserved at -80ᵒC

in brain heart infusion broth with 20% sterile glycerol (C).

(A)

(B)

(C)

Figure 3-1. Prevalence of Campylobacter-positive samples in Trial 1 (A) and Trial 2 (B).

Subsamples positive for Campylobacter is shown in percentage throughout both trials over 912 h

for Trial 1 and 960 h in Trial 2. Pronounced transient reduction of positive Campylobacter

subsamples are shown between 24 h to 96 h, with resumption of positive Campylobacter

subsamples after 120 h.

(A)

100

40 Positive (%) Positive 20

0 -48 0 24 48 72 96 144 336 672

Time (h)

(B)

100 80 60 40

20(%) Positive

12 24 36 48 60 72 84 96

120 144 170 336 504 672 960 Time (h)

Figure 3-2. Percentage of Campylobacter species antimicrobial resistance (AMR) profiles in

Trial 1 over 912 h (A) and Trial 2 over 960 h (B). Blue lines represent pan-sensitive C. jejuni (PS

C. jejuni), orange lines represent nalidixic acid resistant C. hyointestinalis (NalR C. hyo), grey lines represent C. jejuni resistant to nalidixic acid, tetracycline, and ciprofloxacin (TQ C. jejuni),

and green lines represent C. coli resistant to tetracycline and streptomycin (TS C. coli).

(A) 100 80 60 40

20Percentage 0

PS C. jejuni NalR C. hyo Time (h) TQ C. jejuni

(B) 100 80 60

40 Percentage 20 0

PS C. jejuni TS C. coli Time (h)

REFERENCES

1. Acheson D. and Allos B. Campylobacter jejuni Infections: Update on Emerging Issues

and Trends. 2001. Clinical Infectious Diseases.

2. Wesley I., Wells S., Harmon K., Green A., Schroeder-Tucker L., Glover M., and

Siddique I. Fecal Shedding of Campylobacter and Arcobacter spp. in Dairy Cattle. 2000.

Applied and Environmental Microbiology. 10.1128/aem.66.5.1994-2000.2000

3. Lapierre L., Arias M., and Fernandez H. Antimicrobial Resistance in Campylobacter spp.

2016. Campylobacter spp. and Related Organisms in Poultry. 165-183. I 10.1007/978-3-

319-29907-5_10

4. Moore J., et al. 2005. Campylobacter. Vet. Res. 36(3): 351-82. 10.1051/vetres:2005012

5. CDC. Campylobacter (Campylobacteriosis). 2019. CDC.

https://www.cdc.gov/campylobacter/index.html

6. Tang Y., Sahin O., Pavlovic N., LeJeune J., Carlson J., Wu Z., Dai L., Zhang O. Rising

fluoroquinolone resistance in Campylobacter isolated from feedlot cattle in the United

States. 2017. Sci Rep. 7(494). https://doi.org/10.1038/s41598-017-00584-z.

7. Bae W., Kaya K., Hancock D., Call D., Park Y., Besser T. Prevalence and Antimicrobial

Resistance of Thermophilic Campylobacter spp. from Cattle Farms in Washington State.

2005. Applied and Environmental Microbiology. 169-174. 10.1128/AEM.71.1.169–

174.2005

8. Coetzee J, Magstadt D, Sidhu P, Follett L, Schuler A, Krull A, Cooper V, Engelken T,

Kleinheiz M, and O’Connor A. Association between antimicrobial drug class for

treatment and retreatment of bovine respiratory disease (BRD) and frequency of resistant

BRD pathogen isolation from veterinary diagnostic laboratory samples. 2019. PLoS One.

14(12): e0219104

9. Waldner C, Parker S, Gow S, Wilson D, Campbell J. Antimicrobial usage in western

Canadian cow-calf herds. 2019. Can Vet J. 60(3): 255-267.

10. Landers T, Choen B, Wittum T, and Larson E. A review of antibiotics use in food

animals: perspective, policy, and potential. 2012. Public Health Rep. 127(1): 4-22.

11. Holman D, Yang W, Alexander T. Antibiotic treatment in feedlot cattle: a longitudinal

study of the effect of oxytetracycline and tulathromycin on the fecal and nasopharyngeal

microbiota. 2019. Microbiome. 7(86). https://doi.org/10.1186/s40168-019-0696-4

12. Ball J, Kegley E, Sarchet P, and Powell J. Comparison of treatment protocols for bovine

respiratory disease in high risk, newly received beef calves. 2019. Applied Animal

Sciences. https://doi.org/10.15232/aas.2018-01836

13. Gharst G, Hanson D, and Kathariou S. 2006. Effect of Direct Culture Versus Selective

Enrichment on the Isolation of Thermophilic Campylobacter from Feces of Mature

Cattle at Harvest. J Food Prot. 69(5):1024-7. doi: 10.4315/0362-028x-69.5.1024.

14. Smith K., Reimers N, Barnes H.J., Lee B.C., Siletzky R, and Kathariou S. 2004.

Campylobacter colonization of sibling turkey flocks reared under different management

conditions. J. Food prot. 67:1463-1468.

15. Good L, Miller W, Niedermeyer J, Osborne J, Siletzky R, Carver D, and Kathariou S.

2019. Strain-Specific Differences in Survival of Campylobacter spp. in Naturally

Contaminated Turkey Feces and Water. Appl Environ Microbiol. 85:e01579-19.

https://doi.org/10.1128/AEM .01579-19.

16. Heuer O, Pedersen K, Andersen J, and Madsen M. Prevalence and antimicrobial

susceptibility of thermophilic Campylobacter in organic and conventional broiler flocks.

2008. Letters in Applied Microbiology. 33: 269-274. https://doi.org/10.1046/j.1472-

765X.2001.00994.x

17. Yang Y, Feye K Shi Z, Pavlidis H, Kogut M, Ashworth A, and Ricke S. 2019. A

historical review of antibiotic resistance of foodborne Campylobacter. Front Microbiol.

10:1509. 10.3389/fmicb.2019.01509

18. Alfredson D and Korolik V. 2007. Antibiotic resistance and resistance mechanisms in

Campylobacter jejuni and Campylobacter coli. FEMS Microbiol Lett. 277: 123-132.

10.1111/j.1574-6968.2007.00935.x

19. Sproston E, Wimalarathna H, and Sheppard S. 2018. Trends in fluoroquinolone

resistance in Campylobacter. Microb Genom. 4(8): e000198. 10.1099/mgen.0.000198

20. Inglis G, McAllister T, Busz H, Yanke L, Morck D, Olson M, Read R. 2005. Effects of

Subtherapeutic Administration of Antimicrobial Agents to Beef Cattle on the Prevalence

of Antimicrobial Resistance in Campylobacter jejuni and Campylobacter hyointestinalis.

Applied and Environmental Microbiology. 71: 3872-3881. 10.1128/AEM.71.7.3872–

3881.2005

21. (NARMS) National Antimicrobial Resistance Monitoring System. NARMS 2006

executive report. Laurel, MD: U.S. Department of Health and Human Services. 2006.

https://www.fda.gov/media/83619/download

22. Karama M, Kambuy K, Cenci-Goga B, Malahlela M, Jonker A, He C, Ombui J, Tshuma

T, Eltter E, and Kalake A. 2020. Occurrence and antimicrobial resistance profiles of

Campylobacter jejuni, Campylobacter coli, and Campylobacter upsaliensis in beef cattle

on cow-calf operations in South Africa. 7:440-446. Foodborne Pathogens and Disease.

10.1089/fpd.2019.2703.

23. Premarathne J, Anuar A, Thung T, Satharasinghe D, Jambari N, Abdul-Mutalib N, Huat

J, Basri D, Rukayadi Y, Nakaguchi Y, Nishibuchi M, and Radu S. Prevalence and

antibiotic resistance against tetracycline in Camplyobacter jejuni and C. coli in cattle and

beef meat from Selangor, Malaysia. 2017. Front Microbiol. 8:2254.

10.3389/fmicb.2017.02254

24. Fernandez H and Hitschfeld M. Occurrence of Campylobacter jejuni and Campylobacter

coli and their biotypes in beef and dairy cattle from the south of Chile. 2009. Braz J

Microbiol. 40(3): 450-454. 10.1590/S1517-83822009000300005

25. Haruna M, Sasaki Y, Murakami M, Mori T, Asai T, Ito K, and Yamada Y. Prevalence

and antimicrobial resistance of Campylobacter isolates from beef cattle and pigs in japan.

J. Vet. Med. Sci. 75(5): 625-628. 10.1292/jvms.12-0432

26. Sanad Y, Kassem I, Abley M, Gebreyes W, LeJeune J, Rajashekara G. 2011. Genotypic

and Phenotypic Properties of Cattle- Associate Campylobacter and Their Implications to

Public Health in the USA. PLOS One. E25778.

https://doi.org/10.1371/journal.pone.0025778

27. Englen M, Hill A, Dargatz D, Ladely S, Fedorka-Cray P. Prevalence and antimicrobial

resistance of Campylobacter in US dairy cattle. 2006. Journal of Applied Microbiology.

102:6. https://doi.org/10.1111/j.1365-2672.2006.03189.x

28. Englen M, Fedorka-Cray P, Ladely S, and Dargatz D. Antimicrobial resistance patterns

of Campylobacter from feedlot cattle. 2005. J Appl Microbiol. 99(2):285-91.

10.1111/j.1365-2672.2005.02609.x.

29. Kashoma I, Kassem I, Kumar A, Kessy B, Gebreyes W, Kazwala R, and Rajashekara G.

Antimicrobial resistance and genotypic diversity of Campylobacter isolated from pigs,

dairy, and beef cattle in Tanzania. 2015. Front Microbiol. 6:1240.

10.3389/fmicb.2015.01240

30. Cha W, Mosci R, Wengert S, Vargas C, Rust S, Bartlett P, Grooms D, and Manning S.

Comparing the genetic diversity and antimicrobial resistance profiles of Campylobacter

jejuni recovered from cattle and humans. 2017. Front. Microbiol.

https://doi.org/10.3389/fmicb.2017.00818

31. Grove-White D, Leatherbarrow A, Cripps P, Diggle P, and French N. Temporal and

farm-management-associated variation in the faecal-pat prevalence of Campylobacter

jejuni in ruminants. 2010. Epidemiol Infect. 138(4):549-58.

10.1017/S0950268809991051

32. Tang Y, Sahin O, Pavlovic N, LeJeune J, Carlson J, Wu Z, Dai L, Zhang Q. Rising

fluoroquinolone resistance in Campylobacter isolated from feedlot cattle in the United

States. 2017. Sci Rep. 7:494. 10.1038/s41598-017-00584-z

33. Inglis G, Gusse J, House K, Shelton T, and Taboada E. Tetracycline resistant

Campylobacter jejuni subtypes emanating from beef cattle administered non-therapeutic

chlortetracycline are longitudinally transmitted within the production continuum but are

not detected in ground beef. 2020. Microorganisms. 8, 23.

doi:10.3390/microorganisms8010023

34. Lobell R, Varma K, Johnson J, Sams R, Gerken D, Ashcraft S. Pharmacokinetics of

florfenicol following intravenous and intramuscular doses to cattle. 1994. J. vet.

Pharmacol. Therap. 17, 253-258

35. Yang Y, Feye K, Shi Z, Pavlidis H, Kogut M, Ashworth A, and Ricke S. A historical

review on antibiotic resistance of foodborne Campylobacter. 2019. Front. Microbiol.

https://doi.org/10.3389/fmicb.2019.01509

36. Yan M, Sahin O, Lin J, and Zhang Q. Role of the CmeABC efflux pump in the

emergence of fluoroquinolone resistant Campylobacter under selection pressure. 2006. J.

Antimicrob. Chemother. 58, 1154-1159. 10.1093/jac/dkl412

37. Wieczorek K and Osek J. Anitmicrobial resistance mechanisms among Campylobacter.

2013. BioMed Research International. https://doi.org/10.1155/2013/340605

38. http://www.liofilchem.net/en/pdf/mic_brochure.pdf

39. McCrackin, et al 2016. Effect of antimicrobial use in agricultural animals on drug-

resistant foodborne campylobacteriosis in humans: a systematic literature review. 2016.

Crit Rev Food Sci Nutr. 2;56(13):2115-32. 10.1080/10408398.2015.1119798.

40. Sato K, Bartlett P. Kaneene J, and Downes F. Comparison of prevalence and

antimicrobial susceptibilities of Campylobacter spp. isolates from organic and

conventional dairy herds in Wisconsin. 2004. Applied and Environmental Microbiology.

70 (3); 1442-1447. 10.1128/AEM.70.3.1442–1447.2004

41. Ma L, Shen Z, Naren G, Li H, Xia X, Wu C, Shen J, Zhang Q, and Wang Y.

Identification of a novel G2073A mutation in 23S rRNA in amphenicol-selected mutants

of Campylobacter jejuni. 2014. PLOS One. https://doi.org/10.1371/journal.pone.0094503

42. Papich M. Florfenicol. Saunders Handbook of Veterinary Drugs (Fourth Edition): Small

and Large Animals. 2017. Can Vet J. 327-329. https://doi.org/10.1016/B978-0-323-

24485-5.00264-3

CHAPTER 3: Comparison of Campylobacter strains with different antimicrobial resistance

profiles in cattle feces

ABSTRACT

Campylobacter is a leading foodborne pathogen responsible for the diarrheal illness campylobacteriosis. Antibiotic resistance in Campylobacter is often conferred by point mutations; point mutations in the gyrA gene confers high resistance to fluoroquinolones and point mutations in 23S rRNA confers high resistance to macrolides. These point mutations are naturally selected for by the environment; antibiotic selective pressure has been shown to select for fluoroquinolone resistance. Additionally, resistance to fluoroquinolones confers a fitness advantage to C. jejuni. Our objective was to determine whether specific antibiotic resistance in

Campylobacter confers a fitness advantage in cattle feces. Three isolates with different antibiotic resistance profiles (pan-sensitive (PS) C. jejuni, tetracycline- and fluoroquinolone-resistant (TQ)

C. jejuni, and nalidixic acid-resistant C. hyointestinalis) were selected and their survival in feces was measured over several time points at either 4ᵒC or 25ᵒC over 5 and 2 days, respectively.

Survival length differed between temperatures, with a significantly prolonged survival at 4ᵒC over 25ᵒC. At 25ᵒC, the C. jejuni strains declined at a similar rate, while the C. hyointestinalis (C. hyo) declined much slower than the other strains. At 4ᵒC, C. hyo declined much faster than the C. jejuni strains. Overall, C. hyo had a lower survival than the C. jejuni strains at both temperatures.

Temperature at 4ᵒC had more variation in reduction rates between all three strains compared to those at 25ᵒC. Understanding whether a correlation between antimicrobial resistance profiles and survival of Campylobacter in transmission-vehicles, such as feces, exists can potentially help prevent dissemination of Campylobacter.

INTRODUCTION

Campylobacter is a zoonotic organism that has become the leading cause of the foodborne illness campylobacteriosis. Campylobacter colonizes avian species, such as chickens and turkeys, and livestock, such as pigs, sheep, and cattle. This colonization capacity provides a zoonotic route among different animal species and increases the chances of the spread of Campylobacter from farm to farm and from animals to humans (Soro et al., 2020). Poultry is the considered the primary reservoir for Campylobacter and the main food vehicle for campylobacteriosis.

However, cattle have also been implicated as a major reservoir and transmission vehicle for

Campylobacter (Silva et al., 2011, Sanad et al., 2011, Englen et al., 2006). Although campylobacteriosis is self-limited, antibiotics are occasionally used for prolonged or unusually severe clinical symptomology. Overuse of antibiotics in both the clinical and food animal rearing settings has been associated with an increase in antibiotic-resistant strains of Campylobacter

(Silva et al., 2011, Bennani et al., 2019). These antibiotic resistant strains may complicate treatment of human campylobacteriosis, leading to prolonged infections, increased mortality and co-morbidity rates, and increased hospitals costs (Lapierre et al., 2016, Silva et al., 2011).

Antimicrobial resistance is seen as a serious threat to human and animal health with significant economic impacts.

Several mechanisms have been associated with antimicrobial resistance in Campylobacter.

Macrolides and fluoroquinolones have been the most common antibiotics used to treat human infections (McCrackin 2016, Alfredson and Korolik 2009. Resistance to fluoroquinolones in

Campylobacter has been mainly due to mutations in the gyrA gene; specific point mutations have been associated with high resistance levels to ciprofloxacin and nalidixic acid (Alfredson and

Korolik 2007, Engberg et al., 2001). Resistance to macrolides in Campylobacter has been

primarily associated with point mutations in the 23S rRNA gene (Wei and Kang 2018, Engberg et al., 2001). Both macrolide and fluoroquinolone resistance arise from naturally occurring point mutations that are favored or disfavored by environmental conditions. In the presence of antibiotics, these point mutations are selected, allowing this mutation to become dominant (Yang et al., 2019, Luo et al., 2003, McDermott et al., 2002). Mutation frequency rates for resistance to fluoroquinolone have been shown to be significantly higher than those conferring resistance to macrolides (Yang et al., 2019) perhaps correlating with the increased trend of fluoroquinolone- resistant Campylobacter isolates. Although tetracyclines are minimally used for treatment of

Campylobacter, resistance to this antibiotic is frequently seen in Campylobacter spp. (Sanad et al., 2011, Englen et al., 2006, Englen et al., 2005). Resistance to tetracycline is conferred by the tet(O) gene frequently located on self-transmissible plasmids (Wieczorek and Osek 2013).

There has been a general understanding that acquisition of drug resistance, specifically resistance conferred by chromosomal mutations, entails a biological cost for pathogens, altering growth, survival, and transmission inside and outside the host (Andersson 1999). Generally, this means lower fitness in the absence of antibiotic selection pressure compared to non-resistant bacteria.

However, in C. jejuni, fluoroquinolone resistance may confer a fitness advantage over susceptible isolates. Current prevalence of fluoroquinolone-resistant C. jejuni and C. coli in the

USA is 35.4% and 74.4%, respectively (Tang et al., 2017). Concurrently, a rise of nalidixic acid resistance has been seen from 8.2% in 1990 to 26.3% in 2004 (Gallay et al., 2007, Luber et al.,

2003). Similarly, a rise in ciprofloxacin resistance has been seen in the U.S. (Tang et al., 2017,

Yang et al., 2019). A study in Southwestern Alberta, Canada shows an increasing resistance to ciprofloxacin since 2004 with a peak resistance rate of 30% in 2016 (Inglis et al., 2020). With

these rising trends, one is to ask whether this is due to the fitness advantage gained through point mutations conferring fluoroquinolone resistance.

Survival in feces and the environment is critical for transmission in the farm ecosystem and yet, limited information exists on the survival of Campylobacter species to survive transmission- relevant vehicles, such as feces, and more importantly, how the use of antibiotics may affect their survival. In this study, three strains with different antimicrobial profiles were selected: one strain of nalidixic-resistant (NalR) C. hyointestinalis, and one strain each of C. jejuni that was pan- sensitive (PS) and resistant to both tetracycline and fluoroquinolone (TQR). We assessed survival of these three strains in cattle feces at two temperatures, 4ᵒC and 25ᵒC. Understanding the prevalence of Campylobacter species and their antibiotic resistance in cattle feces and understanding if certain strains differ in feces can increase our knowledge of Campylobacter and potentially affect how we can combat the dissemination of Campylobacter, including antibiotic- resistant strains.

METHODS

Bacterial strains and growth media

Strains used in this study included PS C. jejuni, nalidixic acid-resistant (NalR) C. hyointestinalis, and TQ-resistant (TQR) C. jejuni (resistant to ciprofloxacin, nalidixic acid, and tetracycline).

NalR C. hyointestinalis (CSE5221919-2A), PS C. jejuni (CSE52319-1A), and TQR C. jejuni

(CSE52719-1A) were isolated from 0 h, 24 h, and 144 h, respectively, in a florfenicol treatment trial (Trial 1, described in Chapter 2). These strains are hereafter designated as C. hyo, CJ PS, and CJ TQ, respectively. One unknown isolate was sent off for sequencing and species was confirmed to be C. hyointestinalis. Frozen Campylobacter strains were cultured on Mueller

Hinton Agar (MHA) (Becton, Dickinson and Co.) and incubated at 42ᵒC microaerobically for 24 h.

Cattles feces:

All cattle were housed in the same barn, and under the same care and management conditions.

2-24 h.

Assessment of Campylobacter survival in bovine feces:

To measure existing background Campylobacter growth in cattle feces, 1g of cattle feces was suspended in 10 mL sterile diH2O. The suspension was spot enumerated for existing

Campylobacter from undiluted to 10-5 dilution. A volume of 0.1 mL of the undiluted and 0.1 mL of the 10-1 dilution were spread plated on modified charcoal-cefoperazone agar (mCCDA) with the corresponding supplement (Oxoid, Ogdensburg, NY).

Frozen Campylobacter strains were cultured on Mueller Hilton agar (MHA) and incubated at

42ᵒC microaerobically for 24 h. Following incubation, the inoculum of each strain was prepared by suspending 3 loopfuls of each bacterial culture in 3 mL diH2O. Cell suspensions were centrifuged for 10 min at 13,000 RPM, supernatant was discarded, and cells were resuspended in

3 mL of diH2O. Optical density of the bacteria was measured using OD600 and was adjusted by adding diH2O until all cell suspensions had similar OD readings. All cell suspensions were subsequently diluted to 10-8 and spot-plated on MHA.

In three separate 50 ml tubes, 10g of feces were mixed with 1 mL of each inoculum and vortexed until fully homogenized. An amount of 0.1g of the mixture was suspended in 1 mL of diH2O and spot enumerated (10 µl spots) on mCCDA from 10-1 to 10-8 at each time point. While the plates for both trials were incubated at 42ᵒC, feces were stored at either 4ᵒC or 25ᵒC. For survival at

4ᵒC, time points were taken every 24 h. For survival at 25ᵒC, time points were taken every 2 h for the first 6 h and then every 24 h thereafter. Time point 0 h was taken after mixing feces with inoculum. Colonies were enumerated post-inoculation at each time point. Two trials were completed per temperature and duplicate spots were averaged together for data analysis. Due to potential contamination, putative Campylobacter colonies were using microscopy for confirmation. T-test was performed to determine significance of log reduction between strains.

RESULTS

Campylobacter survival in feces was monitored at 25ᵒC and 4ᵒC with two trials for each temperature. During this study, several challenges arose with background bacteria on the selective media (due to background bacteria in feces), resulting in termination of the studies at the specific time points (48 h for 25ᵒC and 120 h for 4ᵒC). Survival length differed between temperatures, with a significantly prolonged survival at 4ᵒC over 25ᵒC (Fig. 1). At 25ᵒC, the C. jejuni strains declined at a similar rate, with an average log reduction of 0.56 for CJ TQ and 0.68 for CJ PS. C. hyo declined much slower with an average log reduction of 0.11 (Fig. 2A). In contrast, at 4ᵒC, C. hyo declined much more rapidly than the other strains with an average log reduction of 0.32 compared to 0.034 for CJ TQ and -0.06 for CJ PS (Fig. 2B). At time point 0 h at 4ᵒC, CJ TQ declined much rapidly than CJ PS even though the original inoculum was similar

(10.3 and 10.6 log CFU/g for CJ PS and CJ TQ, respectively) (Fig. 1B). However, after 24 h,

both C. jejuni strains declined at similar rates. C. hyo had more variation in reduction throughout the 120 h, with a log reduction range between -0.60 and 1.61; the log reduction was the lowest at

0 h (-0.60) and the highest at 72 h (1.61). Overall, C. hyo had a lower survival than the C. jejuni strains at both temperatures (Fig 1). C. hyo did have a lower inoculum count than the C. jejuni isolates at both temperatures but may be due to slightly different ODs.

At 4ᵒC, t-test results indicated that at 24 h and 120 h, there was a significant difference in log reduction between C. hyo and CJ PS. At 25ᵒC, there was a significant difference at 4 h and 6 h between C. hyo and CJ PS. Additionally, there was a significant difference at 2 h between C. hyo and CJ TQ. Although the C. jejuni strains declined similarly at 25ᵒC, there was a significant difference in log reduction at 2 h between the two C. jejuni strains.

DISCUSSION

Mutations conferring antibiotic resistance can entail a cost to pathogens; however, point mutations, specifically to the gyrA gene, have been shown in several studies to confer a fitness advantage to fluoroquinolone resistant C. jejuni. In chickens co-inoculated with fluoroquinolone- resistant and fluoroquinolone-susceptible C. jejuni, the fluoroquinolone-resistant isolates outcompeted the fluoroquinolone-susceptible isolates in the absence of antibiotic selective pressure. Additionally, when mono-inoculated, the fluoroquinolone-resistant isolates did not lose their resistance to fluoroquinolone or their resistance-conferring point mutation in gyrA even in the prolonged absence of antibiotics (Luo et al., 2005). Together, these striking results indicate a fitness advantage from the single point mutation of gyrA that confers high-level resistance to fluoroquinolone in Campylobacter. This increased fitness advantage and high mutation

frequency may contribute to the rapidly increasing trend of fluoroquinolone-resistant

Campylobacter worldwide.

To answer whether these strains with antibiotic resistance differ in fitness in transmission- relevant vehicles such as feces, three Campylobacter strains with different antibiotic resistance profiles were selected. One nalidixic acid-resistant C. hyointestinalis strain and two C. jejuni strains, one pan-sensitive and one resistant to tetracycline, nalidixic acid, and ciprofloxacin (TQ) were selected. Their survival in feces was measured over several time points at either 4ᵒC or

25ᵒC (Figure 1) and a pronounced difference in survival length between the temperatures was seen, 5 days and 2 days, respectively. It is not uncommon to have differences in survival between these two temperatures. Campylobacter spp. have been detected in cattle feces after incubation for 1-3 weeks at 5ᵒC and after incubation for 1 week at 30ᵒC (Olson 2001) and C. jejuni has been known to have a longer survival at 4ᵒC than at 25ᵒC (Solow et al., 2003, Hunt et al., 2000).

Survival was similar between the two C. jejuni strains, while C. hyo had a lower survival throughout both temperatures (Fig 1). C. hyo had a lower starting inoculum at both temperatures which may account for the difference in log CFU/g post inoculation. At 25ᵒC, both C. jejuni strains had similar log reduction, 0.56 for CJ TQ and .68 for CJ PS. There was a slight difference in the log reduction of the C. jejuni strains at 4ᵒC, with a log reduction of 0.034 for CJ TQ and -

0.06 for CJ PS. Although the C. hyo strain declined much slower (log reduction of 0.11) than the

C. jejuni strains at 25ᵒC, it declined much faster at 4ᵒC (log reduction of 0.32). There does not seem to be a correlation between antimicrobial resistance profiles and survival, but species may be a factor in survival at different temperatures. However, we cannot accurately attribute survival results to antibiotic resistance profiles as we do not know the genetic background of the strains.

The strains are most likely not isogenic, except for resistance, which makes it difficult to

compare. If we could take two variants, one PS C. jejuni isolate and one NalR mutant, that are isogenic, except for resistance, we can determine if the antibiotic resistance profiles attributes directly to the survival in cattle feces.

C. jejuni is one of the most prevalent species of Campylobacter found in cattle feces and in human isolates causing campylobacteriosis (Wesley et al., 2000, Tang et al., 2017, Bae et al.,

2005, Lapierre et al., 2016). Key features of C. jejuni that have been linked to survival include biofilms, enzymes, regulators, and flagella (Gundogdu and Wren 2020). It is conceivable that C. jejuni has certain features that enable it to outcompete other species at certain temperatures. The optimal growth temperature of C. jejuni is between 37ᵒC and 42ᵒC; however, C. jejuni has been known to survive at 4ᵒC albeit with lower survival (Haddad et al., 2009).

A major limitation of this study was the background microbes growing on the selective media at certain time points in the trials. Studies have shown that several pathogens, including other bacteria, mold, and fungi often inhabit feces and can potentially outcompete Campylobacter spp., leading to severe contamination after a certain time (Inglis et al., 2010). Other limitations of this study include short period of study, small number of strains, and small number of strains per antimicrobial resistance profile (only one strain per AMR profile was studied). These limitations prevent us from connecting antimicrobial resistance profile to survival.

FIGURES

(A).

9 Survival 25°C

LogCFU/g 6 Inoculum 0 2 4 6 24 48 Time (h) PS C. jejuni NalR C. hyointestinalis TQ C. jejuni

(B).

Survival 4°C 9 8 7 6 LogCFU/g 5 Inoculum 0 24 48 72 96 120 Time (h) PS C. jejuni NalR C. hyointestinalis TQ C. jejuni

Figure 4-1: Survival of Campylobacter hyointestinalis and Campylobacter jejuni in bovine feces. Feces were inoculated with the individual strains in duplicate as described in Materials and

Methods and incubated at (A) 25ᵒC or (B) 4ᵒC. The survival of the three strains for 4ᵒC was calculated over a period of 72 h for the first trial and 120 h for the second trial. The data plotted was an average of duplicate measurements (n=2) for each bacterial species.

(A).

4 Log Reduction 25°C

0 2 4 6 24 48 Log Reduction CFU/g LogReduction -2 Time (h) PS C. jejuni NalR C. hyo (B).

4 Log Reduction 4°C 3 2 1 0

-1 0 24 48 72 96 120 Log Reduction CFU/g LogReduction -2 Time (h) PS C. jejuni NalR C. hyo

Figure 4-2: Log reduction of Campylobacter hyointestinalis and Campylobacter jejuni in bovine feces relative to inoculum. Log reduction was calculated using the survival data shown in Figure

1. Feces were inoculated with the individual strains in duplicate as described in Materials and

Methods and incubated at (A) 25ᵒC or (B) 4ᵒC. Vertical lines represent error bars.

REFERENCES

1. Luo N, Pereira S, Shain O, Lin J, Huang S, Michel L, Zhang Q. Enhanced in vivo fitness

of fluoroquinolone-resistant Campylobacter jejuni in the absence of antibiotic selection

pressure. 2005. Proc Natl Acad Sci USA. 102(3): 541-546. 10.1073/pnas.0408966102

2. Levin BR, Perrot V, Walker N. Compensatory mutations, antibiotic resistance and the

population genetics of adaptive evolution in bacteria. 2000. Genetics. 154(3):985-97.

3. Andersson D, Levin B. The biological cost of antibiotic resistance. 1999. 2(5):489-93.

Curr Opin Microbiol.

4. Luo N, Sahin O, Lin J, Michel LO, Zhang Q. In vivo selection of Campylobacter isolates

with high levels of fluoroquinolone resistance associated with gyrA mutations and the

function of the CmeABC efflux pump. 2003. Antimicrob Agents Chemother. 47(1):390-4

5. McDermott PF, Bodeis SM, English LL, White DG, Walker RD, Zhao S, Simjee S,

Wagner DD. Ciprofloxacin resistance in Campylobacter jejuni evolves rapidly in

chickens treated with fluoroquinolones. 2002. J Infect Dis. 185(6):837-40.

6. Bennani H, Mateus A, Mays N, Eastmure E, Stark K, Hasler B. Overview of evidence of

antimicrobial use and antimicrobial resistance in the food chain. 2019. Antibiotics. 9, 49.

doi:10.3390/antibiotics9020049

7. McCrackin, et al 2016. Effect of antimicrobial use in agricultural animals on drug-

resistant foodborne campylobacteriosis in humans: a systematic literature review

8. Alfredson D and Korolik V. 2007. Antibiotic resistance and resistance mechanisms in

Campylobacter jejuni and Campylobacter coli. FEMS Microbiol Lett. 277: 123-132.

10.1111/j.1574-6968.2007.00935.x

9. Soro A, Whyte P, Bolton D, Tiwari B, Strategies and novel technologies to control

Campylobacter poultry chain: A review. 2020. Wiley. 1-25. 10.1111/1541-4337.12544

10. Wei B and Kang M. Molecular basis of macrolide resistance in Campylobacter strains

isolated from poultry in South Korea. 2018. Food Microbiology.

https://doi.org/10.1155/2018/4526576

11. Engberg J, Aarestrup F, Taylor D, Gerner-Smidt P, and Nachamkins I. Quinolone and

macrolide resistance in Campylobacter jejuni and C. coli: resistance mechanisms and

trends in human isolates. 2001. Emerging Infectious Diseases. 7;1

12. Yang Y, Feye K, Shi Z, Pavlidis H, Kogut M, Ashworth A, and Ricke S. A historical

review on antibiotic resistance of foodborne Campylobacter. 2019/ Front.

Microbiol. https://doi.org/10.3389/fmicb.2019.01509

13. Lapierre L., Arias M., and Fernandez H. Antimicrobial Resistance in Campylobacter spp.

2016. Campylobacter spp. and Related Organisms in Poultry. 165-183.

14. Luber P, Wagner J, Hahn H, Bartelt E. Antimicrobial resistance in Campylobacter jejuni

and Campylobacter coli strains isolated in 1991 and 2001-2002 from poultry and humans

in berlin, Germany. 2003. Antimicrob Agents Chemother. 47(12): 3825-3930.

10.1128/AAC.47.12.3825-3830.2003

15. Gallay A, Prouzet-Mauleon V, Kempf I, Lehours P, Labadi L, Camou C, Denis M, de

Valk H, Descenlos J, and Megraud F. Campylobacter antimicrobial drug resistance

among humans, broiler chickens, and pigs, France. 2007. Emerg Infect Dis. 13(2): 259-

266. 10.3201/eid1302.060587

16. Wieczorek K and Osek J. Antimicrobial resistance mechanisms among Campylobacter.

2013. BioMed Research International. https://doi.org/10.1155/2013/340605

17. Andersson D, Patin S, Nilsson A, and Kugelberg. The biological cost of antibiotic

resistance. 2007. Enzyme-Mediated Resistance to Antibiotics.

10.1128/9781555815615.ch21

18. Wesley I., Wells S., Harmon K., Green A., Schroeder-Tucker L., Glover M., and

Siddique I. Fecal Shedding of Campylobacter and Arcobacter spp. in Dairy Cattle. 2000.

Applied and Environmental Microbiology.

19. Gundogdu O and Wren B. Microbe Profile: Campylobacter jejuni- survival instincts.

2020. Microbiology. 66:230–232. 10.1099/mic.0.000906

20. Olson M. Human and animal pathogens in manure. 2001. In Livestock Options for the

Future National Conference. Agriculture and Agri-Food.

http://www.stopthehogs.com/pdf/pathogens.pdf

21. Inglis G, McAllister T, Larney F, Topp E. Prolonged Survival of Campylobacter Species

in Bovine Manure Compost. 2010. Applied and Environmental Microbiology. 76(4);

1110-1119. 10.1128/AEM.01902-09

22. Haddad N, Burns C, Bolla J, Prevost H, Federighi M, Drider D, and Cappelier J. Long-

term survival of Campylobacter jejuni at low temperatures is dependent on

polynucleotide phosphorylase activity. 2009. App Environ Microbiol. 75(23); 7310-7318.

10.1128/AEM.01366-09

23. Solow B, Cloak O, and Fratamico P. Effect of temperature on viability of Campylobacter

jejuni and Campylobacter coli on raw chick or pork skin. 2003. Journal of Food

Protection. 66(11); 2023-2031. https://doi.org/10.4315/0362-028X-66.11.2023

24. Hunt J, Abeyta C, and Tran T. BAM Chapter 7: Campylobacter. 2000. Bacteriological

Analytical Manual (BAM). FDA. https://www.fda.gov/food/laboratory-methods-

food/bam-chapter-7-campylobacter