Seasonal incidence ofVibrio cholerae was monitored for a year in a man-made freshwater lake, an open sewage canal, and a pond composed of rainwater accumulations, located in Calcutta.V. cholerae was found in all sites. It exhibited a distinct bimodal seasonal cycle in the lake with a primary peak in August-September and a secondary peak in May-June. Correlation with environmental parameters revealed that temperature and, to a certain extent, pH were the important factors governing the densities ofV. cholerae. In the lake, sediment samples harbored high densities ofV. cholerae immediately after months when peak counts were observed in plankton, suggesting a cycle of cells between sediment and water. At the other sampling areas, no defined seasonality was observed. Instead, high counts ofV. cholerae were observed at these severely polluted sites throughout the study period, including the winter months. All the 15 water samples passed via the ligated loop of rabbits yielded pure cultures ofV. cholerae, indicating that the rabbit intestine selects outV. cholerae from a mixed flora. Uniformly high isolation rates ofV. cholerae were observed from brackish water and freshwater species of export quality prawns.V. cholerae was found to be abundant and was represented by 32 individual Louisiana State University (LSU) serovars, including two new serovars. The 01 serovar could not be isolated from any of the samples examined in this study. It was concluded thatV. cholerae non-01 is common in the freshwater environs of Calcutta.

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A comparative study was undertaken of clinical and environmental isolates of non-O1 Vibrio cholerae with respect to their hemagglutinating, hemolytic, enterotoxigenic, and enteropathogenic activities. Cell-associated hemagglutinin titers of the clinical and environmental isolates did not differ much, although the clinical isolates displayed higher cell-free hemagglutinin titers compared with those of environmental isolates. Culture supernatants of 61.5% (24 of 39) of clinical isolates showed hemolytic activity (greater than or equal to 10% lysis of rabbit erythrocytes), while only 33.3% (10 to 30) of the environmental group had such activity. Furthermore, hemolytic activities of the clinical isolates showed a good correlation with their cell-associated hemagglutinin titers which was not true for the environmental group. Culture supernatants of 45.8% (11 of 25) of the clinical and 20% (2 of 10) of the environmental isolates exhibited enterotoxigenic activity in the rabbit ileal loop assay. Such activity was mediated mainly by cholera toxin-like substances, although some of the isolates produced fluid-accumulating factors unrelated to cholera toxin. Experimental animal studies demonstrated that the enteropathogenic potential of the environmental isolates was significantly lower than that of the clinical group. Further analysis of our data showed that phenotypic expression of cholera toxin-like products by the non-O1 V. cholerae isolates was accompanied by their enteropathogenicity. The latter effect was also noted with some of the cholera toxin-negative isolates, particularly in those having high hemagglutinating and hemolytic titers.

Bacterial enteropathogens and rotavirus were sought in 356 cases with acute diarrhoea admitted to the Infectious Diseases Hospital, Calcutta. One or more pathogens were isolated from 74.7% of the cases. Single enteropathogens could be detected from 66% and multiple enteropathogens from 8.7% of the patients. Vibrio cholerae biotype El Tor, rotavirus, V. parahaemolyticus, and enteropathogenic and enterotoxigenic Escherichia coli were the major pathogens detected. Rotavirus was detected from 7.6% of the cases. A higher rate of detection of rotavirus was seen in children younger than two years. Campylobacter jejuni could be isolated from the faeces of six (15%) of 40 cases either as a single pathogen or in association with V. cholerae biotype El Tor.

In a double-blind, randomized clinical trial with 78 adults with acute watery diarrhea and severe dehydration, 37 subjects were positive for Vibrio cholerae. In conjunction with rehydration therapy, 13 patients received norfloxacin, 12 received trimethoprim-sulfamethoxazole (TMP-SMX), and 12 received a placebo. Norfloxacin was superior to TMP-SMX and to the placebo in reducing stool output, duration of diarrhea, fluid requirements, and vibrio excretion. TMP-SMX was no better than the placebo.Acute watery diarrhea caused by Vibrio cholerae is an important cause of hospitalization in Calcutta (6). Several drugs, namely tetracycline (2, 8), furazolidone (5), and trimethoprim-sulfamethoxazole (TMP-SMX) (3), have been found to be effective in reducing stool volume, duration of diarrhea, and vibrio excretion in patients with cholera. Recently, a wide range of bacterial enteropathogens including V. cholerae have been found to be highly susceptible to norfloxacin (4, 7), a 4-quinolone which is similar to nalidixic acid. In this report, we present the findings of a comparative evaluation of the use of norfloxacin, TMP-SMX, or placebo in the treatment of cholera accompanied by severe dehydration.Subjects included in the study were adult male (for ease of collection of stool and urine separately) patients, of more than 18 years of age, who had been admitted to the diarrhea ward of the Infectious Diseases Hospital, Calcutta, with acute watery diarrhea and severe dehydration (11) of less than 24-h duration. Those patients who had received any drug or intravenous fluid before admission or who had any systemic illness were excluded from the study. After enrollment, all patients were placed on cholera cots and were rehydrated with intravenous Ringer lactate and oral rehydration solution as recommended by the World Health Organization (11). A thorough history was taken, a physical examination was performed, and findings were recorded on a prepared form. The amounts of intravenous and oral fluid administered, volume of stool output, and duration of diarrhea were recorded. On admission, a fresh stool sample was collected by using a sterile rectal catheter and was immediately sent to the laboratory for screening of bacterial enteropathogens according to standard techniques (10). Thereafter, rectal swabs collected from all patients for 5 consecutive days were examined for isolation of V. cholerae. All of the V. cholerae isolates were tested for their susceptibility to drugs such as tetracycline, chloramphenicol, ampicillin, TMP-SMX, nalidixic acid, and norfloxacin by the KirbyBauer disk diffusion technique (1). Informed consent was obtained from all patients.Patients included in the study were randomly assigned to one of three treatment groups by using a random number table: group A (n = 26) received norfloxacin (400 mg) twice daily, group B (n = 25) received TMP (160 mg)-SMX (800 * Corresponding author. mg) twice daily, and group C (n = 27) received the placebo twice daily. The two drugs and the placebo were in the form of tablets ...