Multi-drug resistant toxigenic Vibrio cholerae O1 is persistent in water sources in New Bell-Douala, Cameroon

Cholera has been endemic in Douala, since 1971 when it was first recorded in Cameroon. Outbreaks have often started in slum areas of the city including New Bell. Despite the devastating nature of outbreaks, always resulting in high mortality and morbidity, a paucity of information exists on the reservoirs of the causative agent, V. cholerae, and factors maintaining its persistence. This has complicated disease prevention, resulting in frequent outbreaks of cholera. We investigated water sources in New Bell for contamination with V. cholerae O1 with pathogenic potential, to highlight their role in disease transmission. Antibiotic susceptibility pattern of isolates and the environmental factors maintaining its persistence were investigated.

Water samples from various sources (taps, dug wells, streams) were analyzed for contamination with V. cholerae O1 using standard methods. Antibiotic susceptibility was determined by disc diffusion method. Pathogenic potential of isolates was determined by analyzing for genes for cholera toxin (ctx), toxin co-regulated pilus (tcpA), and zonula occludens toxin (zot) by PCR. Physico-chemical characteristics of water (pH, temperature and salinity) were investigated using standard methods. The Spearman's Rank correlation was used to analyze the relationship between physico-chemical factors and the occurrence of V. cholerae O1. Differences were considered significant at P≤0.05.

Twenty-five V. cholerae O1 strains were isolated from stream and well samples in both dry and rainy seasons. Twenty-three (92%) isolates were multidrug resistant. All isolates had genes for at least one virulence factor. Cholera toxin gene was detected in 7 isolates. Of the 15 isolates positive for tcpA gene, two had Classical type tcpA while 13 had tcpA El Tor. All tcpA Classical positive isolates were positive for ctx gene. Isolates were grouped into nine genotypes based on the genes analyzed. pH and salinity significantly correlated with isolation of V. cholerae O1.

Multidrug resistant Vibrio cholerae O1 with pathogenic potential is present in some wells and streams in study area. pH and salinity are among the factors maintaining the persistence of the organism. Findings indicate an urgent need for potable water supply in study area and in addition, regular disinfection of water from contaminated sources to prevent outbreak of cholera.