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MICROBIOLOGY LEGEND
CYCLE 31 ORGANISM 5
Campylobacter jejuni
Campylobacter jejuni is a species of curved, helical-shaped, non-spore forming, Gram-negative, micro-aerophilic bacteria commonly found in animal faeces. It is one of the most common causes of human gastroenteritis in the world. Food poisoning caused by Campylobacter species can be severely debilitating, but is rarely life-threatening. It has been linked with subsequent development of Guillain-Barré syndrome (GBS), which usually develops two to three weeks after the initial illness.
C. jejuni is commonly associated with poultry, and it naturally colonizes the digestive tract of many bird species. One study found that 30% of European starlings in farm settings in Oxfordshire, United Kingdom, were carriers of C. jejuni. It is also common in cattle, and although it is normally a harmless commensal of the gastrointestinal tract in these animals, it can cause campylobacteriosis in calves. It has also been isolated from wombat and kangaroo faeces, being a cause of bushwalkers' diarrhea. Contaminated drinking water and unpasteurized milk provide an efficient means for distribution. Contaminated food is a major source of isolated infections, with incorrectly prepared meat and poultry normally the source of the bacteria.
Disease Infection with C. jejuni usually results in enteritis, which is characterized by abdominal pain, diarrhea, fever, and malaise. The symptoms usually persist for between 24 hours and a week, but may be longer. Diarrhea can vary in severity from loose stools to bloody stools. The disease is usually self-limiting. However, it does respond to antibiotics. Severe (accompanying fevers, blood in stools) or prolonged cases may require ciprofloxacin, erythromycin, azithromycin or norfloxacin. The drug of choice is usually erythromycin. About 90% of cases respond to ciprofloxacin treatment. Fluid and electrolyte replacement may be required for serious cases. Although enteritis and diarrheal syndromes remain the most common manifestations of Campylobacter infections, other diseases have emerged during the past few years.
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P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5 Bryanston Gate, 170 Curzon Road Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za Tel: +27 (011) 463 3260 Fax: +27 (011) 463 3036 Fax to Email: + 27 (0) 86-557-2232 e‐mail : [email protected] Cases of septic arthritis, meningitis and proctocilitis secondary to C. jejuni infection have been reported. There have now been several reports that associate C. jejuni infection with Guillain- Barré syndrome (GBS), an acute demyelinating disease of the peripheral nerves.
Laboratory Identification It may be possible to make a presumptive diagnosis of Campylobacter enteritis by observing characteristic gram-negative, curved, S-shaped, gull-winged, or long spiral forms in Gram-stained preparations of diarrheal stools. One could consider examining wet mounts or stained smears of all diarrheal stool specimens for polymorphonuclear leukocytes and the presence of bacterial forms suggestive of Campylobacter species. Stool specimens for Campylobacter species are not further processed in some laboratories unless polymorphonuclear leukocytes are present. The rationale for this practice is that it is unlikely that Campylobacter species will be recovered in clinically significant numbers in stool specimens devoid of leukocytes. The expenditure of time and use of special culture media for specimens in which there is little chance to recover significant microbes is not considered cost effective.
Successful isolation of C. jejuni from stool depends on the use of selective media (e.g., Campy-Thio, Campy-BAP), incubation at an elevated temperature (42°C), and the proper incubation atmosphere (5% oxygen, 10% CO2, 85% nitrogen). A membrane filtration technique used with non selective blood agar plates has been reported to be as effective as the use of selective media for the isolation of C. jejuni. This method has the advantage of allowing the isolation of antibiotic- sensitive Campylobacter for the past several decades, the selective culture media and special incubation conditions necessary to recover Campylobacter species have been used in most clinical microbiology laboratories. Various procedures can be used to provide a suitable gaseous atmosphere for cultivating micro-aerophilic Campylobacter. These include evacuation-replacement procedures, disposable gas generators, and the use of the Fortner principle.
Gram stain of Campylobacter jejuni Culture on CAMPY blood agar
Identification from culture The appearance of colonies on selective Campylobacter agars that has been incubated at 42°C in the gaseous environment described previously is already presumptive evidence that the organism is one of the thermophilic Campylobacter species (most commonly C. jejuni). The morphology of
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P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5 Bryanston Gate, 170 Curzon Road Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za Tel: +27 (011) 463 3260 Fax: +27 (011) 463 3036 Fax to Email: + 27 (0) 86-557-2232 e‐mail : [email protected] Campylobacter species on selective agar varies from flat, gray, irregular-shaped colonies that may be either dry or moist to colonies that are round and convex and glistening with entire edges. There is tendency for Colonies to form confluent growth along the streak lines on the agar surface. Haemolytic reactions are not observed on blood agar. The identification can be further confirmed by performing rapid catalyse and cytochrome oxidase tests (C. jejuni, C. coli, and C. lari are positive for both), On occasion, thermophilic bacterial species other than Campylobacter species, notably Pseudomonas aeruginosa, may break through and grow on the selective media. It is unlikely; however that P. aeruginosa would be confused with C. jejuni. The colony morphology of the two organisms is different; and if there were any question, a Gram stain would quickly differentiate Campylobacter species from P. aeruginosa.
Gram-stained preparations from colonies of C. jejuni after 24 to 48 hours incubation on blood agar show characteristic gram-negative, curved, ‘S’ – shaped, gull-winged, or long spiral forms, Coccoid forms are more commonly seen in older cultures of C. jejuni, particularly after colonies have been exposed to ambient air. Strict adherence to usual Gram stain timing is important because Campylobacter species are typically faintly staining. For this reason, one could consider extending the staining time of the safranin counterstain to at least 10 minutes to allow for greater staining intensity. Once isolated both subspecies of C. jejuni can be easily identified since they are the only Campylobacter’s that hydrolyze hippurate. In addition, this species is resistant to cephalothin and usually is susceptible to nalidixic acid, although resistant isolates are occasionally encountered.
Treatment Quinolone antibiotics, as Cipro or Levaquin are effective therapy for Campylobacter enteritis, shortening the clinical course by days, with a rapid improvement in patient well being. Dehydrated children may require intravenous fluid treatment in a hospital. The illness is contagious, and children must be kept at home until they have been clear or symptoms for at least two days. Good hygiene is important to avoid contracting the illness or spreading it to others. Intestinal perforation is very rare; increased abdominal pain and collapse require immediate medical attention
References 1. http://en.wikipedia.org/wiki/Campylobacter 2. Koneman’s colour atlas and textbook of diagnostic microbiology, by Washington C. Winn, Elmer W. Koneman.
Questions 1. Discuss the morphological characteristics of Campylobacter jejuni 2. Discuss the role of C. jejuni in disease. 3. Discuss the lab identification of C. jejuni.
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