Seasonal variations in bacterial populations and their antibiotic sensitivity were surveyed in the water of the river Gomati at Lucknow. Most of the bacteria showed an increase in their densities in sewagecontaminated downstream of the river during summer. In contrast, Aeromonas sp. count was found to be higher in upstream during winter. Vibrio cholerae non-Ol was substantially found in downstream only. More than half of the bacterial isolates exhibited antibiotic resistance. The maximum resistance was shown by the winter isolates (36%), particularly from downstream (77.7%). Among the resistant isolates, resistance for ampicillin was predominant (42%), followed by tetracycline (40%). Single and multiple antibiotic resistances were the highest among 32% and 47% of aeromonads, respectively. The double resistance was exhibited to be maximum by the vbrio non-Ol isolates. Disposal of municipal sewage with fecal wastes seems to be mainly responsible for deterioration of water quality along with increased population of pathogenic and antibiotic resistant bacteria in river.Increasing industrialization, urbanization, agricultural and other human activities have caused enormous deterioration in quality of various natural water bodies, particularly rivers in developing countries like India. The waste disposal and land run-off are adversely affecting the ecology and characteristics of riverine microbiota such as aerobic heterotrophs, coliforms, fecal coliforms, enterococci, Aeromonas sp. and Vibrio sp., etc., which generally indicate the extent of riverine pollution (5,8,21,26). As rivers are one of the major sources of water directly or indirectly for human and animal consumption in various ways, riverine pollution has been considered to be a serious health risk.

Pollution indicator bacteria such as coliforms, fecal coliforms, and fecal streptococci were enumerated using a multiple-tube fermentation method in 100 treated drinking-water samples from 20 locations in residential, commercial, and industrial areas of a tropical city during summer. Thirty-four percent of the samples were bacteriologically nonpotable. Maximum coliform-contaminated (27%) samples were derived from industrial areas, while samples contaminated with fecal coliform (23%) and fecal streptococci (20%) originated from commercial areas. Coliforms identified as Escherichia coli, Klebsiella sp., Enterobacter sp., and Citrobacter sp. were present in 29%, 26%, 24%, and 15% of samples, respectively. Fecal coliforms were examined for antibiotic susceptibility with disc diffusion method. All test isolates exhibited multiple antibiotic resistance (MAR) for kanamycin, nalidixic acid, tetracycline, and trimethoprim. Escherichia coli isolates were examined for enterotoxigenicity using the suckling mice bioassay and 60% of the isolates displayed enterotoxigenicity. Data indicate that drinking water contaminated with antibiotic-resistant enterotoxigenic fecal bacteria may be responsible for presence of waterborne diarrheal diseases attributed to therapeutic agents used by urban populations in the tropics.

The total and thermotolerant coliform counts in rural drinking water derived from ground water, piped supplies and surface water are reported for a number of areas in India. To evaluate these counts as indicators of recent faecal contamination the total coliforms and thermotolerant coliforms isolated have been identified. Thermotolerant Escherichia coli formed 11.7% of the total coliforms and 75.1% of the thermotolerant coliforms. Citrobacter sp. (20.4%) and Klebsiella sp. (50.9%) were the other common total coliforms isolated and, among the thermotolerant coliforms, Klebsiella sp. (16.4%) was the only other organism frequently encountered. The total coliform counts were significantly correlated with water temperature. The applicability in tropical areas of standards developed for temperate climates is discussed.

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The findings of this study revealed that very low concentrations of silver ions at pH 8-9 and temperature >20°C have bactericidal efficacy for total disinfection of drinking water. Silver ionisation is suitable for water disinfection and an appropriate alternative to chlorination which forms carcinogenic disinfection by-products.