Monday, November 13, 2006 - 1:30 PM

Prevalence of Antibiotic Resistant Bacteria on Swine Farms.

Yogesh Chander1, Satish Gupta1, Sagar Goyal1, Kuldip Kumar2, and Helene Murray1. (1) University of Minnesota, 1991 Upper Buford Circle, St. Paul, MN 55108, (2) Metrop.Water Reclam.Dist. Chicago, Research and Development MWRDGC, 6001 West Pershing Road, Cicero, IL 60804-4112

Use of antibiotics as growth promoters in animal production systems is considered as one of the major factors responsible for the emergence of antibiotic resistant bacterial strains. This study was undertaken to compare the prevalence of antibiotic resistant bacteria (ARB) on two types of swine farms: ones that use antibiotics as feed additive for growth promotion (AU) and ones where no antibiotics (NAU) are used. From ten farms of each type, samples of manure, soil (from fields where manure was regularly applied as fertilizer) and dog feces (pets on the farm) were collected. Samples were screened for the presence of ARB and percent prevalence of tetracycline and tylosin resistant bacteria calculated. Isolated bacteria (up to 10 colonies from each sample) were identified using 16S ribosomal RNA technique. Susceptibility of isolated bacterial strains to six antibiotics: chlortetracycline, ampicillin, ciprofloxacin, neomycin, bacitracin, and sulfamethoxazole were determined by broth microdilution method. Results showed a higher prevalence of tetracycline and tylosin resistant bacteria in manure samples from AU farms than from NAU farms. However, this difference was not significant in bacteria from soil and dog fecal samples. Also, bacterial isolates from AU farms had higher resistance to chlortetracycline, ampicillin, and neomycin whereas resistance to sulfamethoxazole was widespread in both types of farms. These results suggest that although the use of antibiotics as feed additive on swine farms increases the prevalence of ARB in swine manure, this resistance does not appear to be spreading to rest of the environment, such as fields where manure has been land applied or to pets on the farm.