An official website of the United States government.
<OL> <LI> Identify sources of foodborne pathogens in the farm-to-fork continuum including on-farm, processing and post harvest. <LI> Study the diversity/clonality of foodborne pathogenic strains collected at preharvest, processing and postharvest stages using phenotypic and genotypic methods. <LI> Compare foodborne pathogen load and antimicrobial resistant strain dissemination between pigs raised conventionally and those raised in antimicrobial-free farms. <LI> Disseminate research findings to producers and consumers on the potential sources and necessary precautions to minimize the dissemination of antimicrobial resistant foodborne pathogens.
NON-TECHNICAL SUMMARY: The swine industry is often implicated as one of the most significant contributors to foodborne infections in humans. This group will perform a comprehenive study on the source and diversity of antimicrobial resistant foodborne pathogens in the farm-to-fork continuum.
<P>
APPROACH: The proposed study will encompass three major aspects; preharvest, processing and postharvest, in the farm to fork continuum. At each of these steps, appropriate samples for isolation and identification of three foodborne pathogens will be collected. Foodborne pathogens will be isolated at the laboratories of the 3 investigators who have extensive experience in the area. Phenotypic (antimicrobial susceptibility, serotyping adn phage typing) and genotypic (DNA fingerprinting) characterization methods, which are proven to have high discriminatory power, reproductibility and efficiency. Analysis and interpretation of results will then be conducted using statistical and molecular epidemiology approaches. Results from research will then be transferred to producers (at preharvest), processors (harvest) and consumers (post harvest) through web sites dedicated for the purpose and educational seminars. <P>
PROGRESS: 2006/08 TO 2007/09<BR>
OUTPUTS: Samples were collected from 55 farm-slaughter pairs 20 from North Carolina (10 conventional and 10 antimicrobial free farms), 16 sites from Ohio (9 conventional and 7 ABF) and 19 sites from Wisconsin (6 conventional and 13 ABF). Salmonella prevalence and antimicrobial resistance: Pigs from ABF farms had increased odds of Salmonella detection in farm collected fecal samples compared with conventional farms, (OR= 2.4, p<0.01). No differences were found for carcass swabs. The proportion of Salmonella positive fecal samples among ABF farms was 27.3% and 12.3% for conventional farms. The proportion of resistance detected was as follows- Tetracycline 65.1%, streptomycin 23.5%, amoxicillin/clavulanic acid 22.8%, ampicillin 22.1%, chloramphenicol 16.8%, sulfafizoxazole 4.0%, cefoxitin 4.0%, trimethoprim/sulphamethoxazole 1.3% and kanamycin 1.0%. No resistant isolates were detected for amikacin, ceftriaxone, ciprofloxacin, gentamicin, nalidixic acid or ceftiofur. Campylobacter prevalence and antimicrobial resistance Overall comparison of ABF and conventional herds- There was no significant difference in the prevalence of Campylobacter in swine in the three states (NC (54.2%), OH (54.1%) and WI (58.2%). The prevalence of Campylobacter in conventional farms (56.1%) was not significantly different from ABF farms (54.6%) (p > 0.05). However, the prevalence of Campylobacter in WI farms was higher in conventional farms (70.6%) than ABF (51.5%) (p<0.05). Resistance was observed to all the six antimicrobials tested with different frequency. Tetracycline resistance (66.2%) was the most frequent followed by erythromycin (53.6%). Frequency of resistance to tetracycline and erythromycin was significantly higher in conventional farms (72.1% for tetracycline and 69.5% for erythromycin) than ABF Farms (60.2% for tetracycline and 37.5% for erythromycin) (p<0.05). Resistance to ciprofloxacin (MIC of >4 mg/L) was higher among OH (7.1%) and WI (4.8%) isolates than NC (0.66%). This is the first report of ciprofloxacin-resistant strains of C. coli in ABF pigs in the United States. Yersinia prevalence and antimicrobial resistance Feces and Carcass samples: Yersinia enterocolitica was recovered from 10.9% of fecal samples and of these 36.9% were identified to be harboring the ail gene. North Carolina had the lowest prevalence with 2.5%, while Ohio and Wisconsin had similar Y. enterocolitica prevalence (16.8% and 16.1% respectively). Wisconsin had the highest proportion of isolates as ail positive with 52.6% of Y. enterocolitica isolates harboring the ail gene. Isolation of Y. enterocolitica from carcass samples was rare. Only 4 pre-evisceration carcass samples were positive, and 1 pre-evisceration isolate (25%) was identified to harbor the ail gene. Two carcasses were identified as Y. enterocolitica positive post-evisceration, and one of these isolates was ail positive. Y. enterocolitica was isolated from only 6 carcasses post-chill, and none of these isolates were ail positive. All positive carcass samples originated from either Wisconsin or Ohio.
<P>
IMPACT: 2006/08 TO 2007/09 <BR>
This study is among the very few in the U.S. comparing the prevalence of antimicrobial resistant C. coli from conventional and the antimicrobial-free herds at farm and slaughter stages. It is focused on prevalence, antimicrobial resistance and genotyping. Most of the work regarding Campylobacter is completed and majority of the work on Salmonella and Yersinia has also been completed. Antimicrobial resistance is a major problem in the food safety and public health arena. This study can be used as background information to what the role and impact of antimicrobial use in food animals and its association with antimicrobial resistance. The study resulted in several publications that were published in national and international journals and scientific meetings. Among some of the major points that were found and have significant impact on food animal industry and antimicrobial resistance issues include- The high prevalence of Salmonella among ABF herds as compared to conventional ones. This was done at univariate level and when multivariate models (including various factors not yet considered from the questionnaire) are conducted, the results may be modified. Even though we detected higher number of resistant and multi drug resistant strains in isolates from the conventional system, antimicrobial resistant pathogens commonly isolated from the ABF system (including pentaresistant Salmonella R-type ACSSuT) warrants concern and points to the possible role of other environmental factors in transmission of these strains in pigs. Multi drug resistant ciprofloxacin resistant Campylobacter coli isolates from swine especially from the ABF reared pigs is alarming since this antimicrobial is used in treatment of severe invasive cases of campylobacteriosis.