No abstract

Previous studies have identified enteroadherent Escherichia coli that exhibit localized adherence, diffuse adherence and atypical diffuse adherence as diarrhoeagenic agents associated with infantile diarrhoea in Calcutta, India. In this study, a DNA probe specific for enteroaggregative adherence was used to determine the etiological significance of enteroaggregative E. coli in the causation of diarrhoea. From a total of 330 strains of E. coli recovered from 159 cases of acute secretory diarrhoea and 174 cases of invasive diarrhoea, 20 strains hybridized with the probe, whereas of the 25 E. coli strains recovered from 25 healthy controls only 1 strain hybridized with the probe. Of the 21 probe positive strains, 19 adhered to HeLa cells in the typical stacked-brick pattern while 2 strains recovered from 2 cases of secretory diarrhoea adhered to the glass surface in a hitherto undescribed formation which we have termed, based on the appearance, as the honey-comb pattern. The enteroaggregative E. coli strains identified in this study did not produce any conventional enterotoxins and were significantly associated with patients with secretory diarrhoea (10.7%) than with invasive diarrhoea (1.7%). The results of this study indicate that enteroaggregative E. coli play a causal role in acute secretory diarrhoea in this part of the world which lends credence to the involvement of a potent toxin in the pathogenesis of EAggEC mediated infections.

A highly sensitive bead enzyme-linked immunosorbent assay (bead ELISA) for detection of cholera toxin (CT) was evaluated for direct detection of CT from stool specimens of patients with acute secretory diarrhea. Of the 75 stool samples examined, 59 yielded biochemically and serologically confirmed strains of Vibrio cholerae 01. The bead ELISA was positive for CT in stool supernatants in 50 (84.7%) of the 59 samples from which V. cholerae 01 was isolated. In addition, the bead ELISA was positive for three stool specimens which were negative by culture. The free CT present in 48 of the 50 stool samples positive by culture for V. cholerae 01 and for CT by bead ELISA was completely absorbed by anti-CT immunoglobulin G. All of the 59 strains of V. chokrae 01 biotype eltor isolated in this study produced in vitro CT. The concentration of CT present in the bead ELISA-positive stool samples ranged between 26 pg/mI and >100 ng/ml. This evaluation study demonstrates that the bead ELISA is a sensitive and simple method for direct detection of CT in nonsterile stool samples, and we recommend routine use of this assay for detection of CT in stool samples and culture supernatants in clinical and reference laboratories.

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.

No abstract

For a period of one year (March 1987 to February 1988 , the incidence of Escherichia coli was determined in water, sediment and plankton collected from two sampling sites in a freshwater lake extensively used by humans and animals. Densities of E. coli associated with plankton was the lowest while sediments, especially at site 2, harbored high densities of the organism. Correlation coefficients revealed that the density of E. coli in water samples was linearly correlated to temperature, pH of water, sediment and humidity. Stepwise multiple regression analysis, however, showed that sediment temperature was the dominant variable which could explain 27% of the observed variation in the numbers of E. coli in the overlying waters (p = 0.001). Of the 150 environmental E. coli strains which were characterized, 31 (20.7%) were found to belong to the classic enteropathogenic E. coli (EPEC) serogroups. Seven of the serogroups among the environmental EPEC strains were also encountered from EPEC strains isolated from human cases during a concurrent clinical study. None of the 150 environmental strains were enterotoxigenic or enteroinvasive but 4 strains possessed HEp-2 cell adhesive factor. With the exception of one, all the EPEC strains isolated were multi-drug resistant. From this study, it was evident that the lake is an important source of infection of EPEC and other related diarrheagenic E. coli.

During a 2-year study, Cryptosporidium oocysts were detected in 32 (5.6%) of 566 hospitalized paediatric diarrhoea cases and 2 (1.2%) of 167 non-diarrhoeic individuals. Cryptosporidium was the sole pathogen detected in 17 (3.0%) of the 32 positive cases; in the other 15 it occurred in combination with one or more other established enteropathogen(s). The frequency of detection of the parasite was highest in the 0-6 months age group; no sex-specific difference was discernible. The detection rate of the parasite was highest during the monsoon and post-monsoon months. Most of the patients had watery stools with a mild to moderate degree of dehydration, with the diarrhoea lasting for less than 7 d.

Summary. Escherichia coli adherent to HEp-2 and HeLa cells were isolated from the faeces of 43 (19.7%) of 218 hospitalised infants aged below 6 months with acute diarrhoea. No conventional virulence factors, including enterotoxin production-heat-labile (LT) or heatstable (ST), the verotoxin (VT) or shiga-like toxin (SLT>-or the invasive phenotype (determined by the Sereny test) could be detected among these isolates. Out of the 43 isolates, 16 (37.2%) were of the known enteropathogenic 0: K serogroups-enteropathogenic E. coli (EPEC). The remaining 27 (62.8%) isolates showed different types of adherence to HEp-2 and HeLa cells which was diffuse (40-7%), localised (37.0%), or both (22.3%); they were identified as entero-adherent E. coli (EAEC). The EAEC isolates adhered to HEp-2 and HeLa cells in the presence of mannose, lactose, fucose, galactose, and fetuin, indicating that adhesion was not specific for these sugars or glycoprotein. Haemagglutination and the salt aggregation test (SAT) did not correlate with patterns of adherence. The results of this study indicate that LA-EAEC is an important aetiological agent of acute diarrhoea in infants aged below 6 months in Calcutta.