Virulence factors in environmental and clinical Vibrio cholerae from endemic areas in Kenya.

BACKGROUND: Since 1971, Kenya has had repeated cholera outbreaks. However, the cause of seasonal epidemics of cholera is not fully understood and neither are the factors that drive epidemics, both in Kenya and globally. OBJECTIVES: The objectives of the study were to determine the environmental reservoirs of V. cholerae during an interepidemic period in Kenya and to characterise their virulence factors. METHODS: One hundred (50 clinical, 50 environmental) samples were tested for V. cholerae isolates using both simplex and multiplex polymerase chain reaction. RESULTS: Both sediments and algae from fishing and landing bays yielded isolates of V. cholerae. Clinical strains were characterised along with the environmental strains for comparison. All clinical strains harboured ctxA, tcpA (El Tor), ompU, zot, ace, toxR, hylA (El Tor) and tcpI genes. Prevalence for virulence genes in environmental strains was hylA (El Tor) (10%), toxR (24%), zot (22%), ctxA (12%), tcpI (8%), hylA (26%) and tcpA (12%). CONCLUSION: The study sites, including landing bays and beaches, contained environmental V. cholerae, suggesting that these may be reservoirs for frequent epidemics. Improved hygiene and fish-handling techniques will be important in reducing the persistence of reservoirs.

A study on the geophylogeny of clinical and environmental Vibrio cholerae in Kenya.

Cholera remains a significant public health challenge in many sub-Saharan countries including Kenya. We have performed a combination of phylogenetic and phenotypic analysis based on whole genome DNA sequences derived from 40 environmental and 57 clinical V. cholerae from different regions of Kenya isolated between 2005 and 2010. Some environmental and all clinical isolates mapped back onto wave three of the monophyletic seventh pandemic V. cholerae El Tor phylogeny but other environmental isolates were phylogenetically very distinct. Thus, the genomes of the Kenyan V. cholerae O1 El Tor isolates are clonally related to other El Tor V. cholerae isolated elsewhere in the world and similarly harbour antibiotic resistance-associated STX elements. Further, the Kenyan O1 El Tor isolates fall into two distinct clades that may have entered Kenya independently.