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L. D. GOODRIDGE, Dept. of Animal Science, Univ. of Wyoming, 1000 East University Avenue, Dept. 3684, Laramie, WY 82071-3684 and W. Manley, Microbiologist/Emerging Infectious Diseases, Wyoming Public Health Laboratory, 2300 Capitol Avenue, Cheyenne, WY 82002. The increased use of antimicrobials in food animal production, has created enormous pressure for the selection of antimicrobial resistance among bacteria. While many studies have evaluated resistance in bacterial pathogens, relatively few studies have looked at resistance in commensal bacteria. These bacteria are present in the agricultural environment in numbers far greater than pathogens, and likely play a major role in the harbor and dissemination of antibiotic resistance genes. The objective of this study was to use genome analysis methods to investigate the degree of DNA banding polymorphism exhibited by bovine isolates of antimicrobial resistant commensal Escherichia coli. Fifty bovine isolates of commensal E. coli were evaluated in this study. Each isolate was resistant to at least two antibiotics. Antimicrobial resistance profiles of the E. coli isolates were determined using the Sensititre automated antimicrobial susceptibility system. Ribosomal DNA profiles of the isolates were elucidated by manual ribotyping. Pulsed field gel electrophoresis (PFGE) was performed according to the directions of the Centers for Disease Control and Prevention (CDC). Both PFGE and manual ribotyping clearly resolved the E. coli isolates into distinct clusters. Interestingly, both methods placed multi-drug resistant E. coli isolates (defined in this study as isolates resistant to 3 or more antibiotics) into clusters with other multi-drug resistant isolates. This indicates that a few related clones may be responsible for multi-drug resistance in commensal E. coli. This study describes the possibility that multiple antibiotic resistance phenotypes in commensal E. coli are clonal in nature. It is likely that these clones are involved in the rapid spread of antibiotic resistance among E. coli and other bacteria in the agricultural environment.
Session 33, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |