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This 3 year study is designed to measure the association between the use of five antimicrobial regimens in finishing swine and the presence of antimicrobial resistance in human foodborne pathogens isolated from pigs on farms in the Midwest and their caretakers. <P>
The long-term goals are to measure: <OL> <LI> The occurrence of Salmonella spp. (including Salmonella typhimurium DT104) and Campylobacter spp (including Campylobacter jejuni and coli). <LI> Antimicrobial resistance of fecal E. coli, Salmonella, Campylobacter, and Enterococcus from slaughter-aged pigs. <LI> Gross pathology of pigs that die in the finishing barn. <LI> Health of pigs as determined by evaluation of internal organs at slaughter. <LI> The simultaneous occurrence of Salmonella spp. (including Salmonella typhimurium DT104) and Campylobacter spp and the patterns of antimicrobial resistance between barns of finishinbg swine and their human caretakers.
NON-TECHNICAL SUMMARY: Antimicrobial resistance in pathogens carried by swine may be transmitted to humans. Five antibiotic regimens will be compared in regard to presence of antimicrobial resistance in foodborne pathogens and health of finishing swine.
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APPROACH: We will collect fecal samples from pigs in 110 finishing barns using 5 antibiotic regimens, and also from barn personnel. The barns will be visited once at the beginning of the finishing period and again just prior to when pigs are marketed. At each visit, fecal samples will be collected from 18 randomly chosen pigs, 2 composite barn samples, and the animal caretakers. In vitro antimicrobial susceptibility for Campylobacter, Salmonella and E. coli will be tested using standard commercial testing systems (Etest strips and Microtitre plates). Resistant organisms will be further examined for 3 genes known to code for resistance. Microorganism isolation rates, resistance, health, mortality and productivity factors will be compared between antibiotic regimens.
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PROGRESS: 2001/09 TO 2005/09<BR>
In a large finishing system pigs were given either no antibiotics, 20g/ton tylan continously, 100g/ton tylan for 2 weeks, 50g/ton chlortetracycline continuously or 500g/ton CTC for 2 weeks to see how antibiotic usage affected bacterial prevalence and antibiotic resistance. From each of 80 barns, 20 fecal samples were taken one week after the beginning of the feeding period. Another 20 fecal specimens were taken from pigs at market weight. Pens from which to sample pigs were chosen using a random number table. Fecal specimens were cultured for E. coli and Enterococcus sp. as indicator organisms for Gram negative and Gram positive bacteria. Salmonella and Campylobacter were sampled for their public health importance. In vitro antimicrobial susceptibility testing for Salmonella, Enterococci, Campylobacter and E. coli was performed using broth microdilution methods. In general, Salmonella and Campylobacter were more prevalent at the beginning of the feeding period and at very low levels at the end. Antibiotic feed regimen did not alter the bacterial prevalence or resistance. Detailed final results from Dr. Cray's lab can not be released until MSU transfers committed funding to USDA, but are prepared for publication as soon as transfer is complete. Another extension may be necessary to allow budget requirements to be met.
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IMPACT: 2001/09 TO 2005/09<BR>
Producers will not be able to alter antibacterial resistance by utilizing different feeding strategies and the minor contribution at this point in the food chain suggests giving attention to other food processing strategies.