Antimicrobial Sensitivity of Shiga toxin-producing Escherichia coli (STEC) and Virulence Genes of Representative Isolates in Port Harcourt, Nigeria

Aim: To assess the antimicrobial susceptibility, Shiga toxin-producing Escherichia coli (STEC) and virulence genes of representative isolates in some selected sites of Port Harcourt, Nigeria.

Study Design: Case-controlled study.

Place and Duration of Study: Selected places in Port Harcourt, Rivers State, Nigeria, between November, 2020 to November, 2021.

Methodology: Three hundred and forty-nine (349) samples were analyzed, 80 meat and 63 waste waters from five abattoirs cited in the city, 46 meat samples from five selected roadside butchers sites in the city, 109 patients stool samples, 30 stool samples from food sellers, 20 stool samples from healthy subjects and 1 commercial bottled water which served as control samples. A combination of methods was employed: conventional culture using Tryptone soya broth as an enrichment media, chromagar STEC and serology with O157 latex reagents. Multiplex polymerase chain reaction analysis was used to screen for the presence of specific virulence genes in representative isolates and 16SrRNA sequence data was used to confirm the identity of isolates. GraphPad Prism 2.01 was used to perform the statistical analysis and p values < 0.05 were considered statistically significant.

Results: The results showed that 20 (100%) of the selected isolates profiled for virulence gene harbored a combination of stx1 + stx2, while 45% carried the eaeA gene. The culture and molecular methods used in STEC detection showed a good level of agreement comparatively. The result of isolates sequenced for identification by targeting the 16S gene and compared with publicly available sequences on NCBI for phylogenetic analysis showed 100% identities to the ribosomal RNA gene of seven uncultured Escherichia coli strains with Gene Accession numbers (CP049290, MN208208, KY780343, CP058233 MK641327, CP082357, CP082129, MH346270). Isolates were resistant to Ceftazidime 98.9%, Cefuroxime 100%, Cefixime 100%, Augmentin 100% and sensitive to the quinolones and nitrofuratoin. The virulence gene combination pattern, the antibiogram pattern and the phylogenetic analysis result indicated genetic relatedness of isolates.

Conclusion: The representative isolates harbored stx1 and stx2 combination, only 45% harbored stx1, stx2 and eaeA genes combination. Phylogenetic analysis of the representative isolates confirmed the genetic similarity of isolates.