Search for Escherichia coli O157:H7 and Other Enterohaemorrhagic Escherichia coli in Diarrhoeal Cases in Abuja, Nigeria

Abstract

Aims: To detect the sporadic involvement of shiga toxin producing Escherichia coli (STEC) O157:H7 or any other enterohaemorrhagic E. coli in gastro-intestinal (diarrhoeal) infections. Study Design: The study is a cross sectional survey for bacterial causes of diarrhoea in the study area. Place and Duration of Study: The study was conducted over a six months period (January to July) within Abuja, Nigeria. Methodology: One hundred and six faecal samples were collected and analyzed. Direct inoculation of diarrhoeal stool samples on Sorbitol MacConkey agar and Cefixime-Tellurite Sorbitol MacConkey agar for the isolation of E. coli O157: H7 alongside Enrichment culture in modified peptone water followed by immunomagnetic separation (IMS) with magnetic beads coated with an antibody against Escherichia coli O157 was used. For the identification of non-O157 STEC among the Non-sorbitol fermenting E. coli isolated, PCR for virulence markers was carried out. Verocytotoxicity Assay was used to detect free faecal toxin in the stool samples for the identification of other Enterohaemorrhagic E. coli (EHEC) infections. Routine methods were used for the isolation and identification of bacterial isolates in the specimens. Results: Enteric bacterial pathogens detected in the study include V. cholerae (1.9% of subjects), S. typhi (1.9%), S. paratyphi B (0.95%), S. paratyphi C (0.95%), unidentified Shigella species (0.95%), Shigella dysenteriae A1 (1.9%), Shigella flexneri (4.7%). No E. coli O157:H7 was isolated. Eleven NSF E. coli isolated and screened for shiga toxin/verocytotoxin (st/vt) genes via PCR and latex agglutination tests were negative. However, free faecal toxin was demonstrated in 16 (15.09%) of the 106 faecal samples analyzed indicating the possible involvement of non-O157 VTEC in diarrhoeal diseases. None of the non-sorbitol fermenting E. coli was found to be STEC. Conclusion: Findings mean that none of the sorbitol-negative E. coli isolated from this study is VTEC/STEC. Results point to the presence of non-O157 VTEC in the study area. This pathogen should be considered as a routinely sought after agent in diarrhoeal illnesses especially among children.