The First Detection of Florfenicol Resistant Gene in Shiga-like Toxin Producing Escherichia coli Isolated from Pork in Korea

Introduction: Florfenicol is fluorinated derivative of chloramphenicol and represent highly protein inhibitors of bacterial protein biosynthesis. It is used in veterinary medicine or feed additives for pigs in Korea. The transfer of antibiotic resistance gene among the bacterial strains has become a problem worldwide, so drug resistant bacterial phenotypes should be identified.

Purpose: In this study, antimicrobial resistance and resistance gene were investigated for Escherichia coli, especially Shiga-like toxin producing E. coli (STEC) isolated from pork in Korea.

Methods: We monitored 301 pork samples in slaughter houses and retail markets, and isolated 50 strains of E. coli. Among these isolates, six isolates resulted in STEC. Minimum inhibitory concentration (MIC) on six strains was performed for 14 antibiotics, ampicillin, amoxicillin/clavulanic acid, cefoxitin, ceftiofur, cephalothin, florfenicol, ciprofloxacin, colistin, gentamicin, nalidixic acid, neomycin, streptomycin, tetracycline and trimethoprim/sulphamethoxazole, and three strains showed high MIC to florfenicol and chloramphenicol (64 µg/ml). PCR was conducted to detect the florfenicol resistant gene (floR) and the chloramphenicol resistant gene (cat).

Results: All of 3 strains contained the floR, while none of them had the cat. These PCR products were sequenced and aligned to obtain homology with other available genes in reference GenBank. A BLAST search showed that they contained sequences with homology to the floR gene of E. coli or Salmonella enterica serovar Heidelberg.

Significance: This is the first report to detect floR gene in STEC isolated from slaughtered pigs in Korea. These results suggest that some STEC isolates in Korea carry florfenicol resistant gene.