Detection of LT and ST genes in the Escherichia coli isolated from the dogs, sheep and poultry

Abstract

This study was designed to identify if the heat-labile enterotoxin (LT)-, heat-stable enterotoxin (ST)a- and STb-encoding genes are detectable in faecal samples from different healthy hosts and also on which part of the genome (chromosome or plasmid) they are located. Seventy-five samples of Escherichia coli were isolated from dog, sheep and poultry faecal samples (25 from each host). Plasmid and chromosomal DNA were extracted and polymerase chain reaction performed on all plasmid and chromosomal DNA using LT, STa and STb primers. Additionally, the plasmid profile of all E. coli isolates was defined using gel electrophoresis. The results showed that 36% of the E. coli isolates possessed genes for the production of LT toxin. All samples were negative for STa and STb genes. The plasmid profile of different hosts showed that all samples harboured plasmids. The results of this study indicate that enterotoxigenic E. coli are present in the faeces of different hosts. Since the genes encoding for LT and ST toxins reside on plasmids, or occasionally on transposons, they may transfer among the Gram-negative bacteria especially to the enterobacteriaceae family including E. coli which then may infect other hosts, for example, humans.