Ecological study of Vibrio cholerae in Vellore

Vellore is endemic for cholera due to Vibrio cholerae O1 and O139. In a pre vious study the prevalence of Vibrio cholerae in drinking water, lakes and sewage outfalls in a single 2-months period in Vellore, India was determine d. In addition water samples from three sites were also tested for the pres ence of V. cholerae O1 and O139 by fluorescent antibody staining. This foll ow on study has examined how the environmental distribution of V. cholerae at the same sites alters over a 12-month period and the relationship to the clinical pattern of cholera in Vellore, Samples of water were collected fr om fixed sites at three water bodies each month between April 1997 and Marc h 1998. Bacteria isolated from samples were identified by standard biochemi cal tests and isolated strains of V. cholerae tested for their ability to a gglutinate O1 and O139 antisera. Samples were also tested for the presence of V. cholerae O1 and O139 by fluorescent antibody staining. The clinical i solation rate of V. choler ae in Vellore, maximum temperature and rainfall were also studied. The results demonstrate the presence in the environment of viable but non-cultivable (VNC) V. cholerae in 10 of 12 months of the st udy year as well as their viability. Their prevalence in the environment al so correlated with the isolation of these pathogens from clinical samples o ver the same study period.