In situ survival of Vibrio cholerae and Escherichia coli in a tropical rain forest watershed.

For 12 months, Vibrio cholerae and fecal coliform densities were monitored along with nine other water quality parameters at 12 sites in a rain forest watershed in Puerto Rico. Densities of V. cholerae and fecal coliforms were not significantly correlated, even though the highest densities of both bacteria were found at a sewage outfall. High densities of V. cholerae were also found at pristine sites at the highest point in the watershed. The density of Escherichia coli and V. cholerae in membrane diffusion chambers did not change significantly during the course of two such studies. Physiological activity, as measured by electron transport system activity and relative nucleic acid composition, indicated that both E. coli and V. cholerae remained active. This study suggests that V. cholerae is indigenous to tropical fresh waters and that assays other than those that detect fecal coliforms or E. coli must be used for assessing public health risk in tropical waters.