Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2006
Publication Date: 6/1/2007
Citation: Englen, M.D., Hill, A.E., Dargatz, D.A., Ladely, S.R., Cray, P.J. 2007. Prevalence and antimicrobial resistance of campylobacter in u.s. dairy cattle. Journal of Applied Microbiology. 102(6):1570-1577. Interpretive Summary: The emergence of food-borne bacterial pathogens such as Campylobacter that are resistant to antimicrobials has become a significant problem worldwide. Two species, Campylobacter jejuni and C. coli, account for the great majority of human infections. In the present study, the prevalence of Campylobacter and its susceptibility to eight antimicrobials was examined in U.S. dairy cattle from 21 states. Nearly 98% of the 96 dairy operations sampled were positive for Campylobacter and Campylobacter was isolated from 51% (735/1435) of all fecal samples. Notable resistance to tetracycline (48.2%), nalidixic acid (4.3%), and ciprofloxacin (3.0%) was observed with C. jejuni, while C. coli showed resistance to all antimicrobials tested except chloramphenicol and ciprofloxacin. The C. coli isolates also had significantly higher levels of resistance to macrolides and tetracycline compared to C. jejuni. Campylobacter coli appears to acquire antimicrobial resistance more readily than C. jejuni. Although Campylobacter is common in U.S. dairy cattle, this livestock source has not proven to be a major source of human infection. This work is useful to producers, regulatory agencies, and researchers in food safety and antimicrobial resistance. It provides valuable new information on the prevalence and antimicrobial resistance of an important food-borne pathogen from a major sector of the U.S. food supply.
Technical Abstract: Objective: To obtain an overview of the prevalence and antimicrobial resistance of Campylobacter in feces of U.S. dairy cows in 2002. Methods and Results: Feces from 1435 cows, representing 96 dairy operations in 21 U.S. states, were collected for culture of Campylobacter. A total of 735 Campylobacter strains were isolated (51.2% positive samples) with 94 operations positive (97.9%) for Campylobacter. From this collection, 532 isolates (473 C. jejuni and 59 C. coli) were randomly selected for susceptibility testing to eight antimicrobials: azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid and tetracycline. The C. jejuni isolates exhibited resistance to tetracycline (47.4%), nalidixic acid (4.0%), and ciprofloxacin (2.5%), while the C. coli strains exhibited resistance to all antimicrobials except chloramphenicol and ciprofloxacin. Only 3.6% of the C. jejuni isolates were resistant to two or more antimicrobials but 20.3% of the C. coli strains were multi-resistant. Conclusions: On most operations, at least one cow was positive for Campylobacter and more than half of the cows sampled were shedding Campylobacter. The C. coli isolates had significantly higher levels of resistance to macrolides and to tetracycline compared to the C. jejuni strains, but were susceptible to ciprofloxacin. Significance and Impact of the Study: This study demonstated a high prevalence of Campylobacter on U.S. dairy operations; however, U.S. dairy cattle have not been recognized as a major source of human infection compared to poultry. Campylobacter coli appears to develop antimicrobial resistance more readily than C. jejuni from the same environment.