Emergence and detection of gastro-enteric virulence genes in non-pathogenic Vibrio cholerae: Implications for public health and water safety in African developmental regions

Background

Water, an indispensable component of life, has in recent times been associated with the distribution/spread of gastro-enteric diseases especially as safe water is a concern in Southern, Eastern and Western African developmental regions.

Methods

This study evaluated the molecular fingerprints of potential gastro-enteric associated virulence genes of 58 somatic antigen non-agglutinating Vibrio cholerae 1/139 (SA-NAG-Vc-1/139) strains from domestic water sources. Strains were isolated and characterized applying both culture-based-microbiological techniques and molecular-fingerprinting of target-specific identification genes using simplex/multiplex PCR assay and ERIC-PCR fingerprints.

Results

Our study revealed diverse gene-based indices vis T3SS (29/58, 50.00%), T6SS (33/58, 56.9%), rtxA (37/58, 63.79%), rtxC (12/58, 20.69%), NAG-stn/sto (13/58, 22.41%), prtV (17/58, 29.31%), hlyA (41/58, 70.69%), nanH (40/58, 68.97%), mshA (44/58, 75.86%), chxA (37/58, 63.79%), hapA (17/58, 29.31%), ace (22/58, 37.93%), and cep (20/58, 34.48%) etc. Such results show that 53.45% (31/58) of isolates harboured more than three virulence associated genes while nanH, mshA, chxA, T6SS, T3SS, rtxA, hlyA, mshA, chxA, ace and cep fingerprints were detected predominantly with corresponding ilea-loop test positive strains. ERIC-PCR also showed multiple target specific repetitive intergenic consensus sequence regions ranging from 2 to 8.

Conclusions

This is an indication that the previously known non-pathogenic strains now harbour potential gastro-enteric virulence which may be controlled by more than one virulent gene dynamics. It also suggests a current potential shift in the virulence dynamics of V. cholerae strains recovered from the study area and a re-evaluated view of the previously non-pathogenic V. cholerae strains. Furthermore, the presence of such genes in SA-NAG-Vc-1/139 strains indicates a potential public health related concern. Although these detected potential gastro-enteric associated genes may be implicated in sporadic gastroenteritis, our result has re-emphasized their probable public health concern as they may be involved in both endemic and severe gastroenteritis cases, which suggests the need for water routine monitoring or surveillance.