Antibiotic resistance and genotypic characterization of Escherichia coli isolated from pig farm environment

The use of antibiotics, including therapeutically in human and veterinary medicine, or as prophylaxis of growth promotion in animal husbandry, ultimately exerts selective pressure favorable for the propagation of antibiotic resistant bacteria. In this study we have determined the resistance for antibiotics of E. coli from pig farm environment, and investigate genetic relatedness by random amplification of polymorphic DNA (RAPD). Six farms were randomly selected in Gyeongsanman-do and Busan provinces for collecting samples from feces, manure and underground water. A total of 88 isolates from feces, 74 isolates from manure and 1 isolate from underground water were analyzed by antibiotic resistance and RAPD. Antibiotic resistance testing was performed by disk diffusion method using 16 antibiotics. The highest percentage of antibiotic resistance of isolates from feces and manure was found to the following antibiotics; tetracycline (100% and 100%), sulfamethoxazole/trimethoprim (60.2% and 62.2%), streptomycin (50.0% and 68.9%), chloramphenicol (56.8% and 56.8%), ampicillin (50.0% and 81.1%) and cephalothin (50.0% and 51.4%). Of isolates from feces and manure, 22.7% and 20.3% showed multiple resistance to 4 and 5 antibiotics, respectively. The isolates from GE pig farm showed six RAPD patterns. A single pattern, RAPD-C, was predominat in feces isolates (50.0%) and manual isolates (46.7%), and the rest of feces isolates showed RADP-A, B and E pattern and manure isolates showed D and E pattern. One isolate from underground water showed F pattern. The appearance of multiresistant in E. coli isolates from pig farms environment is a problem of major concern of public health and RAPD may offer an useful tool of discrimination for the epidemiological investigation.