Version 3: Comparative analysis of virulence gene profiles of Escherichia coli from clinical and non-clinical sources in Rivers State, Nigeria

Traditionally, the presence of virulence features have been thought to be a key factor in differentiating pathogenic from commensal strains. An understanding of virulence potential of Escherichia coli isolates from various sources is essential to help shed light on potential contamination/transmission rates between the various sources. This study was therefore aimed at exploring the occurrence of specific virulence genes and gene profiles associated with Escherichia coli from clinical and non-clinical sources in Rivers State, Nigeria.

Two hundred samples from clinical (urine and feces) and non-clinical (soil and poultry droppings) sources (50 each) were analyzed using standard microbiological procedures. DNA was extracted from isolates presumptively identified as Escherichia coli using PrestoTM Mini gDNA Bacteria-Kit Quick protocol following the manufacturer’s instructions. Isolate identities were confirmed using E. coli specific 16S rRNA primers and confirmed isolates screened for the presence of six virulence genes (Afimbriae binding adhesin (afa), type 1 fimbriae (fimH), P-fimbrial Usher Protein (papC)), iron acquisition systems: aerobactin (aer), Cytotoxic necrotizing factor I (cnf1) and alpha hemolysin (hly).

Results showed that all isolates haboured at least one of the tested virulence genes, with fimH (97%) as the most prevalent virulence gene and papC the least commonly occurring (35%). A higher occurrence of virulence genes was noted in non-clinical isolates though hly and cnf were not detected at all in any of the isolates studied (0%). Ten different profiles were observed with the afaCc-aer-fimH profile the most commonly occurring virulence gene profile in general (33.3%). For non-clinical isolates however, the aer-afaCc-fimH-papC was the most commonly occurring profile (42.9%).

This study shows that the test Escherichia coli from clinical and non-clinical sources do not carry distinct virulence gene profiles. Studies on a larger subset of isolates would however be necessary to determine if indeed the virulence genes tested for in this study really cannot be used to tell whether an isolate is from a clinical source or not in the South-South of Nigeria.