The prevalence of <e1>Vibrio</e1> spp. in drinking water and environmental samples in Vellore South India

The prevalence of <e1>Vibrio cholerae</e1> in drinking water, lakes and sewage outfalls during July and August 1996 in Vellore, India was determined. Drinking water samples were collected on single occasions from 12 sites in different geographic areas of the town where cholera had been reported. Samples of water, plankton and sediment were collected from fixed sites at three lakes on three occasions separated by at least 3 days during the course of the study. Samples from open sewers were taken from two representative sites in four areas of the town. Bacteria isolated from samples were identified by standard biochemical tests and isolated strains of <e1>V. cholerae</e1> tested for their ability to agglutinate O1 and O139 antisera. Water samples from lakes were also tested for the presence of <e1>V. cholerae</e1> O1 and O139 by fluorescent antibody staining. Non-O1, non-O139 strains of <e1>V. cholerae</e1> were detected in 41% of drinking water samples and 100% of water, sediment and plankton samples from the test lakes. Eighty-seven per cent of open sewers sampled contained viable non-O1, non-O139 <e1>V. cholerae</e1>. Fluorescent antibody staining gave positive results for <e1>V. cholerae</e1> O1 and O139 for all water samples from the three lake sites. Strains of <e1>Aeromonas</e1> spp. were isolated from 58% of drinking water samples and from 66% of sediment, 77% of plankton and 55% of water samples from lakes. All open sewers sampled contained <e1>Aeromonas</e1> spp. PCR amplification employing specific primers demonstrated that none of the non-agglutinating <e1>V. cholerae</e1> isolates contained the <e1>ctx</e1> operon. The non-O1, non-O139 <e1>V. cholerae</e1> isolates showed different patterns of antibiotic resistance to ampicillin, ciprofloxacin, chloramphenicol, tetracycline and trimethoprim.