MOLECULAR CHARACTERIZATION AND GASTROINTESTINAL TRACT ECOLOGY OF COMMENSAL HUMAN FOOD-BORNE BACTERIAL PATHOGENS IN THE CHICKEN
Location: Poultry Microbiological Safety Research
Title: Campylobacter coli naturally resistant to elevated levels of gentamicin as a marker strain in poultry research
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 8, 2009
Publication Date: June 1, 2009
Citation: Cox Jr, N.A., Richardson, L.J., Berrang, M.E., Cray, P.J., Buhr, R.J. 2009. Campylobacter coli naturally resistant to elevated levels of gentamicin as a marker strain in poultry research. Journal of Food Protection. 72(6):1288-1292.
Interpretive Summary: In order for adequate development of intervention and a reduction in Campylobacter spp. colonization rate of broiler flocks, an improved understanding of the ecology and physiology of Campylobacter spp. in poultry is needed. Developing and using suitable Campylobacter strains in research projects as markers could allow for studies to be conducted that are currently not feasible or very difficult to conduct. Performing inoculation studies with characterized strains of Campylobacter presently available requires utilization of molecular techniques to determine the similarity of the isolates obtained and the isolates used for inoculation in the study and is both costly and time consuming. In the current study, a C. coli strain that was resistant to gentamicin at 400ug/ml allowed for evaluation of strain as a potential Campylobacter marker organism. The C. coli strain was efficacious in inoculation studies within poultry and could be used for numerous future inoculation or research studies.
Inoculation studies with Campylobacter are limited without a suitable marker. The purpose of the study was to screen Campylobacter strains (n>2,000) obtained from poultry carcass rinses through the National Antimicrobial Resistant Monitoring System (NARMS) for resistance to gentamicin and evaluate a specific strain’s efficacy as a marker. A C. coli strain was resistant to gentamicin above 32ug/ml. Gentamicin was incorporated into media (Campy-cefex, Brucella, and blood agar) from 0 to 1000 ug/ml and the strain streaked to determine gentamicin resistance. The C. coli strain’s upper level of growth on Campy-cefex plates was 400 ug/ml, on blood agar plates was 300 ug/ml, and brucella agar plates was 200 ug/ml. Ceca and post-pick carcass rinses were obtained and streaked onto Campy-cefex agar with the above gentamicin levels to evaluate extraneous microflora exclusion. Campy-cefex agar containing gentamicin prevented from the ceca and reduced from the rinse extraneous microflora. The C. coli strain was orally or intracloacally inoculated into day-of-hatch chicks. At 1, 3, and 6 wks-of-age, inoculated broilers were removed and several tissue types sampled for strains presence. At 6 wks-of-age, 10 additional pen-mates were sampled. The C. coli strain readily colonized chicks, disseminated to body tissues, colonized pen-mates and persisted throughout the 6 week grow-out. The C. coli strain was readily isolated by drag-swabs from the litter within the pens. The C. coli strain’s unique characteristic, being resistant to high levels of gentamicin allows for a marker which can be used in a wide range of Campylobacter research projects.