Comparative analysis of virulence gene profiles of Escherichia coli from human and non-human sources in Rivers State, Nigeria

Traditionally, the presence of virulence features has been thought to be a key factor in differentiating pathogenic from commensal strains. An understanding of the virulence potential of isolates from various sources is essential to 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 from human and non-human sources in Rivers State, Nigeria. Two hundred samples from human (urine and faeces) and non-human (soil and poultry droppings) sources (50 each) were analysed using standard microbiological procedures. DNA was extracted from isolates presumptively identified as using the Presto Mini gDNA Bacteria-Kit Quick protocol following the manufacturer's instructions. Isolate identities were confirmed using -specific 16S rRNA primers, and confirmed isolates were screened for the presence of six virulence genes [afimbriae binding adhesin ( ), type 1 fimbriae ( ) and P-fimbrial usher protein ( )], iron acquisition systems: obactin ( ), cytotoxic necrotizing factor I ( ) and alpha-hemolysin ( ). Results showed that all isolates harboured at least one of the tested virulence genes, with (97%) as the most prevalent virulence gene and the least commonly occurring (35%). A higher occurrence of virulence genes was noted in non-human isolates, though and were not detected at all in any of the isolates studied (0%). Ten different profiles were observed with the profile the most commonly occurring virulence gene profile being in general (33.3%). For non-human isolates, however, was the most commonly occurring profile (42.9%). This study shows that the test from human and non-human sources do not carry distinct virulence gene profiles. Studies on a larger subset of isolates would however be necessary to determine if the virulence genes tested in this study really cannot be used to tell whether an isolate is from a human source or not in the South-South of Nigeria.