Epidemiology and antimicrobial resistance of Campylobacter spp. in food animals and humans in northern Thailand.

摘要

Campylobacter spp. have been recognized as major foodborne pathogens in developed and developing countries. Recently, Campylobacter spp. with resistance to antimicrobial agents have been identified in various parts of the world, including Thailand. It is also widely speculated that the use of antimicrobial agents in food animals may be contributing to the antimicrobial resistance problem in humans. Because there was limited information on Campylobacter spp. in food animals in Thailand, and to determine whether food animals were an important source of Campylobacter spp. with resistance to antimicrobial agents, a study was designed to address six objectives: (1) validate the use of a fluorogenic PCR assay to identify C. jejuni from field samples; (2) determine the frequencies and the antimicrobial susceptibility level of Campylobacter spp. isolated from food animals and farm workers at farms, slaughterhouses, and markets; (3) compare the frequencies of Campylobacter spp . with resistance to antimicrobial agents in food animals, food products and farm workers; (4) determine what risk factors associated with the observed frequencies of antimicrobial resistance; (5) determine whether antimicrobial use in feed and treatment on pig and chicken farms is associated with the frequency of antimicrobial resistance in Campylobacter; and (6) determine the association between mutation in the gyrA gene of C. jejuni and level of resistance to ciprofloxacin.; A combination of cross-sectional and prospective study designs were used. Samples were collected from pigs and chickens at the farm, slaughterhouse, and market in 2000 and 2001. Farm and slaughterhouse worker stool samples were also collected. Isolation of Campylobacter spp. was done using enrichment and selective media, and suspect colonies were confirmed using oxidase test, catalase test and gram staining. In vitro susceptibility testing was done using the microbroth dilution technique, for ciprofloxacin, erythromycin, gentamycin, azithromycin, clindamycin, chloramphenicol, nalidixic acid, and tetracycline. Results of susceptibility testing were reported in minimum inhibitory concentrations (MICs), and isolates were classified as resistant based on breakpoints from the National Committee for Clinical Laboratory Standards. Fluorogenic PCR was used to identify C. jejuni and the Thr-86-to-Ile mutation in the gyrA gene of C. jejuni.; The prevalence of Campylobacter spp. in pigs was found to be 73.6% at the farm, 45.6% at the slaughterhouse, and 24.6% at the market. In chickens, the prevalence was 73.4% at the farm, 40.6% at the slaughterhouse, and 47.2% at the market. In humans, the prevalences of Campylobacter spp. were 12.5% and 0% in pig farm workers and chicken farm workers, respectively. Resistance was found to all antimicrobial agents tested in chickens and pigs at farms, slaughterhouses and markets. The most prevalent forms of resistance seen were to ciprofloxacin, nalidixic acid, and tetracycline. The prevalence of resistance was higher for those antimicrobial agents to which animals were exposed. There was very high agreement between ciprofloxacin resistance and the presence of the Thr-86-to-Ile mutation in gyrA gene.