[Isolation and quantification of Salmonella in the waters of the Río de la Plata destined for recreation].

Thirty three samples from recreational waters from different areas of Río de la Plata were tested for Salmonella (Fig. 1). A 200 ml sample filtered through a diatom bed as well as 2 and 20 ml samples without filtering were studied using a simple and economical technique. The isolation probability was directly dependent on the water volume analyzed. Best results were obtained when tetrathionate broth with novobiocin and Salmonella shigella agar were used (Table 3). Salmonella was isolated from 36% of the samples studied and 12 serotypes were identified (Table 5). The relation between the NPM of each bacteriological indicator used and the NPM of Salmonella are shown in Table 4. Correlation values were calculated by relating mean point logarithms of the classes in Table 4 with the isolation percentages of Salmonella for each class. These values were low, except for fecal Streptococcus (R2 = 0.94). The high density of fecal coliforms found in Bagliardi and Pescadores Beaches (rarely less than 10.000 bacteria/100 ml) and the incidence of Salmonella, lead us to conclude that these waters are unsafe for bathing and swimming, specially for children, according with the international recommendation on the quality of recreational waters. Waters with the characteristics described here should be periodically analyzed for Salmonella concentration. The lack of correlation values between the MPN of total and fecal coliforms and the MPN of Salmonella, also supports this advise.