Escherichia coli was isolated from fish grown in a pond that had never been exposed to antibioticsupplemented feeds (control group), and from fish on an integrated farm, fed for 6 wk with manure of chickens that received tetracycline-supplemented and chloramphenicol-supplemented feeds. E. coli was also isolated from these chickens after being fed such for 23 d. The antibiograms of the isolates were determined using the disk diffusion method. The prevalence of E. coli isolates from fish and chickens on the integrated farm that were resistant to tetracycline and chloramphenicol, to trimethoprim-sulfamethoxazole, gentamicin, ciprofloxacin and amoxicillin were significantly higher (p \u3c 0.05) than those from fish in the control farm. In addition, the diversity of resistance was also greater among E. coli from the integrated farm group, which concurs with the results of other studies that exposure to antimicrobials results in higher prevalence of resistant isolates as a consequence of positive selection. On the other hand, the prevalence of resistant E. coli from fish and chickens on the integrated farm that received and those that did not receive antibiotics in their feeds were not significantly different (p \u3e 0.05), indicating that exposure to antimicrobials was not required for the occurrence and maintenance of resistant strains. The data suggest that prevalence of antimicrobial resistant strains is a result of the dynamic interplay of environmental and host-specific factors
