Comparison of lactose fermenting and lactose non-fermenting Escherichia coli isolates from healthy poultry feces

Abstract

This study compared the characteristics between lactose fermenting and lactose non-fermenting Escherichia coli (E. coli ), with 48 strains of each isolated from healthy poultry feces. Antibiotic resistance and multidrug resistance (MDR) were assessed using 21 antibiotic agents by the disc diffusion method, and pathotypes were identified by PCR targeting virulence genes such as LT , STa , STb , Stx1 , Stx2 , eaeA , bfpA, aggR, and ipaH. As a result, ampicillin and carbenicillin resistance rates were higher in lactose non-fermenting E. coli than in fermenting E. coli . Similar resistance patterns were observed for the other antibiotics, regardless of whether the isolates were lactose fermenting or not. Besides, most of the isolates in this study showed MDR. In PCR reactions, only LT , STb , and eaeA genes were amplified using gene-specific primers, while the others were not. In the detection of the LT gene in enterotoxigenic E. coli , 6 isolates of lactose fermenting E. coli possessed plasmid DNA only, whereas both genome and plasmid DNA were detected in two isolates each of lactose non-fermenting E. coli . For STb , only genomic DNA was detected in 21 lactose fermenting and 15 lactose non-fermenting E. coli isolates. In the eaeA PCR, six lactose-fermenting isolates were positive in genomic DNA and six in plasmid DNA, with none positive in both. In lactose non-fermenting isolates, eleven were positive only in genomic DNA, and eight were positive in both.