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Colonization factor antigens I and II (CFA/I and CFA/II) are important in the pathogenesis of diarrhea in humans caused by some enterotoxigenic Escherichia coli (ETEC). Plasmid DNA from 16 CFA/I+ and five CFA/II+ ETEC were examined by Southern blot analysis with enterotoxin gene probes and were compared with plasmid DNA from derivatives of the same ETEC that had lost the ability to produce these colonization factors. Among the 16 CFA/I+ ETEC strains, the loss of CFA/I was accompanied by the loss of a plasmid of between 34 and 68 megadaltons (MDa) coding for heat-stable enterotoxin A2 (ST-A2) in 12 strains, by the loss of a 60-MDa plasmid coding for heat-labile enterotoxin (LT) and ST-A2 in one strain, or by deletions of a segment of DNA encoding for ST-A2 in three strains. Among five CFA/II+ ETEC strains, the loss of CFA/II was associated with the loss of a plasmid of 75 MDa coding for LT and ST-A2 in three strains, with the loss of genes coding for LT and ST-A2 from a 68-MDa plasmid in one strain, or with no discernible loss of a plasmid or DNA sequences coding for enterotoxins in the remaining strain. The loss of CFA/I and CFA/II production was associated with the loss of DNA sequences encoding for ST-A2 in 20 of 21 ETEC examined.

Rotavirus was identified as the only etiological agent in 5% of adults (28 of 526) with diarrhea who were admitted to Bamrasnaradura Hospital in Nonthaburi, Thailand, during a 1-year period. Infection was determined by detection of rotavirus in diarrheal stools by enzyme-linked immunosorbent assay accompanied by a greater than fourfold rise in serum complement fixation and radioimmunoassay antibody titers to rotavirus. Adults with clinical rotavirus infections were as severely ill as patients with most bacterial enteric infections; only patients with cholera passed more watery stools and were more dehydrated than those with rotavirus infections. Only 2 of the 28 adults with rotavirus infections had known recent contact with young children with diarrhea. Rotavirus infections in these adults occurred most frequently in the cooler, drier months in Thailand than during the rest of the year. In some settings, rotavirus should be considered in the differential diagnosis of severe diarrhea in adults as well as in young children.

Enteropathogenic Escherichia coli (EPEC) was isolated from 11% of 148 Hmong children under 1 year old with diarrhea at a refugee camp in northern Thailand. Of 16 children with EPEC-associated diarrhea, 11 were infected with EPEC that adhered to HeLa cells in a diffuse pattern, 3 were infected with EPEC that adhered to HeLa cells in a localized adherence (LA) pattern, and 2 were infected with EPEC that were nonadherent. In Bangkok, EPEC was isolated from 6% of 64 children under 1 year old with diarrhea and 7% of 56 children of the same age without diarrhea. Of four children with diarrhea, two were infected with EPEC with an LA pattern, and two were infected with nonadherent EPEC. Of four children without diarrhea, one was infected with EPEC with an LA pattern, one was infected with EPEC that adhered in a diffuse pattern, and two were infected with nonadherent EPEC. The 21 EPEC isolates with an LA pattern hybridized with the EPEC adherence factor DNA probe. EPEC was the only enteric pathogen identified in 16 (80%) of 20 children with EPEC-associated diarrhea. EPEC was as frequently isolated from children under 1 year old as were other bacterial enteric pathogens. The problem of identifying EPEC with pools of polyvalent antisera are described, and the need to identify additional enteropathogenic determinants of EPEC is discussed.

Alkaline phosphatase-conjugated (AP) 26-base oligonucleotide DNA probes were compared with the same probes labeled with gamma-32P for the identification of heat-labile (LT) and heat-stable (ST) enterotoxigenic Escherichia coli (ETEC). The AP oligonucleotide probes were as sensitive as the radiolabeled (RL) probes in detecting LT and STA-2 target cell DNA, but the AP ST probe, which differed from STA-1 by two bases, was less sensitive than the RL probe in detecting STA-1 DNA (6.25 versus 0.78 ng). Of 94 ETEC that were identified with the RL probe, the AP probes detected 93% (28 of 30) of ST, 73% (25 of 34) of LT, and 67% (20 of 30) of LTST ETEC. When colony lysates of these ETEC were examined, the AP probes identified all 94 ETEC. In examinations of stool blots, the RL and AP probes were shown to have sensitivities of 71 and 59%, specificities of 91 and 86%, positive predictive values of 87 and 73%, and negative predictive values of 86 and 74%, respectively. AP oligonucleotide probes to detect ETEC were less sensitive in detecting ETEC by colony or stool blot hybridization than the RL probes but could be used by laboratories without access to radioisotopes to examine colony lysates.