[Frequency of vibrio cholerae isolation from water and plankton of the lower Salado river basin (Santa Fe, Argentina)].

In the lower Salado River Basin 85 samples of water and 40 of plankton were collected from January 1993 to December 1996. In the 69.4% of the water samples and in the 75% of the plankton samples Vibrio cholerae was detected. None of the isolate strains belonged to O1 and O139 serogroups. The seasonality in the frequency of isolation of V. cholerae tested by multiple proportions comparison test was not confirmed (p > 0.05). There were significant differences (p < 0.05) between the isolation frequencies found in the Salado River (85 samples, 69.4%) and those found in the Paraná River environments (16 samples, 25%) and in municipal waste effluents (18 samples, 33.3%).