Nasal Carriage of Methicillin Resistant Staphylococcus Aureus in Livestock and Farm Workers in Two Communities in Lagos, Nigeria Adesida, Solayide A.,1* Oke, Anu-Oluwapo O.,2 Amosun, Elizabeth A.3 and Coker, Akitoye. O.4 1 Department of Microbiology, Faculty of Science, University of Lagos, Akoka, Lagos, Nigeria. 2 Department of Medical Microbiology and Parasitology, College of Medicine, University of Lagos, Idi-araba, Lagos, Nigeria. 3 Department of Veterinary Microbiology, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Oyo State, Nigeria. 4 Department of Microbiology and Parasitology, Babcock University Teaching Hospital, Ilishan-Remo, Ogun State, Nigeria. * Corresponding Author: Dr. Adesida, Solayide A., Department of Microbiology, Faculty of Science, University of Lagos, Akoka, Lagos, Nigeria; Phone: +234 8024924343; Email: [email protected] ABSTRACT The epidemiology of methicillin resistant Staphylococcus aureus (MRSA) is dynamic and the associated public health risk is likely to increase in settings where there is close interaction between humans and animals. This study assessed the occurrence of antimicrobial resistance among S. aureus from livestock and farm personnel, and estimated methicillin-resistance among the isolates. Two hundred and fifty (250) nasal specimens were collected from sheep, goats, cows and farm personnel who had contact with the animals in two farms in a sub- urban region within Lagos State. Antibiotic susceptibility test was performed using disk diffusion method. The presence of mecA and mecC gene was determined by PCR. S. aureus was recovered from 141 (56.4%) of the 250 nasal samples analyzed: 32 (22.7%) from cows, 25 (17.7%) from sheep, 32 (22.7%) from pigs, 24 (17.0%) from goats and 28 (19.9 %) from farm workers. Ten isolates, consisting of 4 from cows (8%), 3 from pigs (6%), and 3 from farm personnel (6%), were positive for MRSA. The human-MRSA were recovered from pig workers (2) and a cow farm worker (1). All MRSA strains were resistant to at least three different antimicrobial categories. The MSSA strains were classified into thirteen antibiotypes of various subtypes. mecC – MRSA was not detected. The high frequency of S. aureus with phenotypic multidrug resistance traits encountered in this study presents a major public health issue. Thus, practices directed at minimizing the burden of antimicrobial resistance in farm animals should be initiated. Keywords: Colonization; Farm Personnel; Livestock; Staphylococcus aureus INTRODUCTION are often carriers and rarely infected (5), but have the capabil- Staphylococcus aureus has been implicated in a variety of in- ity for disseminating the pathogen in the general population. In human, the bacterium is often carried asymptomatically fections in humans and animals. The organism represents at various body sites and such carriage could increase the a serious public health burden in hospital and community risk of developing infections as well as assist in spreading settings, as well as an economic and animal welfare problems the pathogens to other humans. It is a notable cause of skin in farm animals. It is a major cause of S. aureus mastitis in and soft tissue infection, bacteraemia and food poisoning in cows (1, 2) and may lead to great economic losses in the humans (6). dairy industry. For chickens, S. aureus is associated with severe The persistence and virulence of S. aureus are con- infections including comb necrosis, bacterial chondronecrosis sequences of its increased antibiotic selective pressure. with osteomyelitis, septicaemia and ‘‘bumble foot’’ (3, 4). Pigs Methicillin-resistant S. aureus (MRSA) is the most frequently Israel Journal of Veterinary Medicine Vol. 74 (1) March 2019 Multidrug resistant Staphylococcus aureus in Farm Settings 23 Research Articles described antibiotic resistant strain with ability to acquire of human S. aureus isolates (21-22). In addition, the use resistance to various classes of antibiotics and virtually to all of antimicrobial agents in animal production is a common β-lactam antibiotics (7). For the past 25 years, high domi- phenomenon (23). In the South-East region of the country, nance of MRSA has been consistent in hospitals globally the antibiotic susceptibility test of S. aureus from goats, sheep, (8). Furthermore, large reservoirs of Community-associated cow, pigs and rabbits revealed that 79% of the S. aureus strains (CA) MRSA strains existing outside health care facilities were resistant to one or more of the antimicrobial agents are increasingly reported as significant pathogens in many tested (24). Also, examination of S. aureus from bovine countries (9). However, a recent shift in MRSA epidemiology mastitic milk in the North-Central region of the country involves its emergence in animals including pets and live- revealed that only two out of the twenty six (7.6%) isolates stock (10). This variant designated as Livestock-associated examined were positive for mecA-MRSA (25). However, MRSA (LA-MRSA) was discovered in early 2000 among much less is known about the animal reservoirs of MRSA pigs and pig farmers in the Netherlands (11). Ever since, a in the South-western region. considerable number of studies in several European coun- Lagos, a metropolitan city, is characterised by intensive tries, USA and Asia have focussed on LA-MRSA (11, 12). livestock (especially poultry and pigs) farming practices in the Other reservoirs of LA-MRSA include cattle, poultry and sub-urban region. This could be a huge problem considering wild animals (10, 13). recognition and spread of the new MRSA strains among food Like other MRSA variants, LA-MRSA is assumed animals and their human contacts worldwide (26). Therefore, to be multidrug resistant in nature, displaying resistance we were prompted to evaluate the presence of MRSA in β to ≥3 antimicrobial classes in addition to -lactams (14, cattle (sheep, goats, and cows), pigs and their human contacts 15). It differs from HA-MRSA and CA-MRSA in its in two farms located in the sub-urban region of Lagos State. genomic composition (16) and could harbour the mecA We aimed to determine the antibiotic susceptibility patterns homologue or the mecC (originally called mecALGA251), of the isolates and the occurrence of mecA- and mecC-MRSA which has 70% similarity to mecA at the DNA level (17). strains. Generally, the mec gene encodes for an altered form of penicillin-binding protein (PBP), which has a reduced MATERIALS AND METHODS affinity for beta-lactam antibiotics. At amino acid level, mecC encodes PBP2c and has about 63% amino acid Study Area and Sampling homology with PBP2a (17). Basically, mecA – positive We studied two livestock hubs in two communities in Lagos, MRSA strains have been detected in animals, humans Nigeria. Both sites are approximately 23.8 km apart. The and the environment and they may harbor virulence genes centers were selected due to cattle and pigs rearing activi- which can complicate the development and management ties. Although, information on the total population of the of infections (6). Similarly, human acquisition of MRSA livestock on the farms was not ascertained, management carrying mecC could occur as a result of direct contact with operations are based on private-public partnership between livestock, contaminated environment or food products the State and individuals. Samples were collected based on (18). Its zoonotic transmission potential was reported in consultation and consents of the personnel who had direct Spain where a patient with mecC-positive MRSA sepsis contacts with the animals. Furthermore, permission was ob- died in the emergency department (19). In another study, tained from the Lagos State Ministry of Agriculture prior Petersen et al. (20) provided evidence of transmission to sampling. Nasal samples were randomly collected from and development of infections in two persons who had two hundred (200) animals and fifty (50) farm workers. The contact with cows and sheep carrying mecC MRSA strains. farm workers assisted with the collection of samples from The authors inferred that mecC-carrying MRSA can be the animals. The procedure for specimen collection was non- exchanged between humans and ruminants. invasive and there was no observable scar inflicted on the In Nigeria, mecA-MRSA colonisation and infection is subjects during the process. All human participants signed a widespread problem and a large number of studies have informed consent forms. All processes were closely supervised focused on the phenotypic as well as genotypic analyses by one of the investigators. 24 Adesida, Solayide A. Israel Journal of Veterinary Medicine Vol. 74 (1) March 2019 Research Articles Bacterial Isolation and Identification Table 1: Staphylococcus aureus isolated from animal and human sources The nasal swab was collected from both nostrils of each Sample Source No. of Samples Frequency of Collected S. aureus isolation (%) animal and participating farm personnel using sterile cotton- Farm Personnel 25 16 (6.4%) tipped swabs. Specimens were transported immediately to Cows 50 32 (12.8%) the Microbiology laboratory. The swabs were incubated for Sheep 50 25 (10%) o 24h at 37 C in brain heart infusion broth (Oxoid, UK) and Goats 50 24 (9.6%) then streaked onto mannitol salt agar and incubated at the Pigs 50 32 (12.8%) same conditions. Colonies were purified and stored at -20OC Farm Personnel 25 12 (4.8%) in 10% glycerol-brain heart infusion broth for subsequent Total 250 141 (56.4%) analysis. Presumed colonies of S. aureus were