Diarrheal diseases are highly prevalent in Bangladesh. However, the relative contribution of diarrheagenic Escherichia coli organisms-those that are enterotoxigenic (ETEC), enteropathogenic (EPEC), enteroinvasive, enterohemorrhagic, enteroaggregative, and diffuse adherent-to diarrhea in Bangladeshi populations is not known. With DNA probes specific for these diarrheagenic E. coli strains, we analyzed fecal E. coli from 451 children up to 5 years of age with acute diarrhea seeking treatment at a Dhaka hospital and from 602 matched control children without diarrhea from July 1991 to May 1992. Enteroinvasive E. coli was not isolated from any children; enterohemorrhagic E. coli was not isolated from any diarrheal children but was isolated from five control children; enteroaggregative and diffuse adherent E. coli strains were isolated with similar frequencies from children with and without diarrhea, thereby showing no association with diarrhea; ETEC was significantly associated with diarrhea in the diarrheal children as a whole and especially in the age groups of 0 to 24 months and 37 to 48 months (further analysis suggests an association with diarrhea for the heat-stable toxin only and for both heat-labile-and heat-stable-toxin-producing ETEC only); and EPEC was significantly associated with diarrhea in the diarrhea group as a whole and particularly in infants up to 1 year of age. Further analysis suggested that EPEC strains of only the traditional serogroups were significantly associated with diarrhea. ETEC and EPEC infections peaked during warm months. Our data thus suggest that EPEC and ETEC are important causes of acute diarrhea in children in this setting.

Aeromonas isolates from patients with diarrhea in Bangladesh (n ‫؍‬ 69), from healthy controls (n ‫؍‬ 11), and from surface water (n ‫؍‬ 40) were analyzed with respect to their hybridization groups (HGs) by the aid of fatty acid methyl ester (FAME) characterization and DNA fingerprinting by AFLP, biochemical phenotypes (Phe-nePlate [PhP] types), and the production of hemolysin and cytotoxin. The aim of the investigation was to find out whether certain strains carrying virulence factors predominated among patient isolates. According to FAME and/or AFLP analysis, most human isolates were allocated to DNA HGs 4 (Aeromonas caviae) and 1 (A. hydrophila). Most environmental strains were allocated to HG8 (A. veronii biogroup sobria) and HG4 (A. caviae), and only one was of HG1. According to PhP typing, the diversity among patient isolates was lower than that among other strains, and two dominating PhP types (types BD-1 and BD-2) were identified in 29 and 30% of the patient isolates, respectively. PhP type BD-1 was also common among the environmental isolates, whereas PhP type BD-2 was only identified in two of the other isolates. Twenty-five of 26 isolates belonging to HG1 were of the same PhP type (BD-2), whereas isolates of other common HGs were more diverse according to their PhP types. Hemolytic and cytotoxin-producing strains occurred more frequently among the environmental isolates than among patient isolates. However, the hemolytic and cytotoxic activities among human isolates was strongly correlated to the HG1/BD-2 type, which, in addition, showed high cytotoxin titers (median values, 1/512 compared to 1/128 for cytotoxin-positive isolates belonging to other types). Thus, the HG1/BD-2 type may represent a pathogenic A. hydrophila type that is able to produce diarrhea in humans.

We undertook a controlled study of children younger than 5 years in Bangladesh to determine whether enterotoxigenic Bacteroidesfragilis (ETBF) was associated with diarrhea in this population. ETBF was isolated from 22 (6.1%) of 358 patients and 5 (1.2%) of 425 controls (P = 0.0001). In children younger than 1 year, however, low isolation rates (2 to 3%) were found in both patients and controls. In children older than 1 year, the rates were significantly higher in children with diarrhea (16 [9%] of 177) than in controls (2 [1%] of 264; P = 0.00001). When children with mixed infections with other known diarrheal pathogens were removed, the differences in children older than 1 year were still significant (7 [4%] of 177 versus 2 [1%] of 264; P = 0.033). The syndrome associated with ETBF was secretory in nature, with watery diarrhea, and of mild severity. These epidemiological and clinical findings are similar to those from a previous study of White Mountain Apaches in the United States and are the first to suggest that ETBF may also be an important diarrheal pathogen in other geographic areas and in the developing world where diarrhea is highly endemic.

We have developed a microtiter enzyme-linked immunosorbent assay method for detecting the heat-labile enterotoxins of Vibrio cholerae and Escherichia coli using GM, ganglioside as the base coat. This method compares favorably with a similar assay using anticholera toxin as the base coat, and with the Y, adrenal cell assay. The assay should be useful in detecting enterotoxin production in E. coli and vibrios (including non-agglutinating Vibrio), in quantitating the toxin, and in determfining binding properties of enterotoxins to ganglioside. The assay can also be used to quantitate antibodies which block the attachment of the toxin to the ganglioside. Several methods are available to detect the heat-labile enterotoxin of Escherichia coli or Vibrio cholerae. These can broadly be grouped into assays which depend on toxin activity (i.e., rabbit intestinal loop [11], permeability in rabbit skin [2], Y, adrenal cell [9], Chinese hamster ovary [CHO] cell [7], and other tissue culture assays [4]) and immunological assays (e.g., staphylococcal coagglutination [1], passive immune hemolysis [3], radioimmunoassay [6], and

The role of cytolethal distending toxin (CDT)-producing Escherichia coli, a newly described category of E. coli, in the causation of diarrhea was studied by screening E. coli isolates from 546 children <5 years of age with diarrhea and 215 matched controls without diarrhea by using a specific DNA probe. Although CDTpositive E. coli strains were isolated from more children with diarrhea than from healthy controls (3.1 versus 0.93%), this difference did not reach statistical significance (P ‫؍‬ 0.082). All CDT-positive strains also possessed the virulence factors of enteropathogenic E. coli or enteroaggregative E. coli isolates.