Antimicrobial susceptibility patterns of Escherichia coli in diarrheal piglet fecal samples: using continuous medicated feed and geographical variation

Abstract

The aim of this study was to determine the minimal inhibitory concentrations (MIC) of antimicrobials against Escherichia coli by broth microdilution method and study antimicrobial sensitivity patterns for E. coli isolated from diarrheic piglets in pig farms that regularly use medicated feed. Total of 120 fecal swabs were collected from 3 conventional pig farms, located in Ratchaburi and Kanchanaburi provinces, for E. coli isolation. Only 114 samples (95.0%) were able to be isolated, 93.8% non-hemolytic E. coli and 6.2% hemolytic E. coli. Enrofloxacin showed the lowest MIC90 (1 μg/ml), while the most susceptibility of E. coli was apramicin (100%). The sensitivity patterns of Farm 1 and 2 were not different, however, their sensitivity patterns were different from Farm 3 (P<0.05). The present result showed that there was no relationship between feed medication and E. coli antimicrobials resistance in piglets. In conclusion, apramycin and enrofloxacinwere the most effective antimicrobial, considering sensitivity test in order to treat infection with E. coli. Whereas, lincomycin, and tylosin were the most resistance (100%).