Molecular identification of virulence and antibiotic-resistant genes in Escherichia coli O157 and non-O157 recovered from water samples

Abstract

Background: This research work focused on ascertaining the presence of virulence and antibiotic-resistant genes in Escherichia coli (E. coli) O157 and non-O157 recovered from drinking water sources. Methods: Identification of E. coli O157 and non-O157 was carried out using standard serological and PCR techniques. Virulence genes (rfb O157, fliC H7, stx1, stx2, eae and hly genes) and antibiotic-resistant gene (BlaTEM) were detected using PCR method on selected isolates (n= 15) from different water sources which demonstrated multiple antibiotic-resistance in a previous study. Results: The serological identification result revealed that a total of 68 out of 382 E. coli isolates, recovered in a previous work, were identified as a presumptive E. coli O157. These included 19.1 %, 21.7 %, 33.3 %, 14.3 % and 9.1 % of E. coli isolates from wells, boreholes, sachets, streams and pipe-borne respectively. Statistical analysis revealed that there was no significant difference in the frequency of E. coli O157 from the different water sources (p > 0.05). Also, there was a statistically significant positive correlation between the E. coli isolates and E. coli O157 (Pearson’s r = 0.996). Detection of virulence and antibiotic-resistant genes showed that only 46.7 %, 33.3 %, 33.3 %, 93.3 %, and 66.7 % carried rfb O157, fliC H7, stx1, stx2 and rpoS gene respectively. In contrast, all the isolates possessed hly and BlaTEM genes but none had eae gene. Conclusion: The presence of one or combination of these genes in these isolates depicts their virulence and resistance nature.