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Samples (1,318) of enterotoxigenic Escherichia coli (ETEC) isolated in 1994-1995 from children with diarrhea from Nepal, Indonesia, Peru, and Thailand were examined for colonization factor antigen (CFA) and coli surface (CS) antigens. Fifty-five percent of 361 heat-labile and heat-stable (LT-ST), 14% of 620 LT-only, and 48% of 337 ST-only ETEC had CFA/CS antigens. LT-ST ETEC strains were predominantly in the CFA II group, and ST only strains were in the CFA IV group. Additional studies are needed to identify ETEC strains that do not have CFA/CS antigens.

In developed countries, serotypes (or G types) have been identified in > 70% of group A rotavirus using monoclonal enzyme immunoassays (MEIAs); however, these assays have identified < 50% of rotavirus G types from developing countries presumably because the VP7 antigens were damaged by freezing and thawing during transportation of specimens. The VP7 (G) serotypes of rotavirus in unfrozen stool collected from children with acute diarrhea in Bangkok were determined using MEIA and compared to hybridization with alkaline phosphatase-labeled oligonucleotide probes. Reverse transcription of dsRNA coding for VP7 followed by polymerase chain reaction amplification of cDNA was used as an additional step prior to hybridization for 98 specimens that did not hybridize with the oligonucleotide probes. Of 251 rotavirus specimens, 208 (83%; 99% Cl = 76-89%) hybridized with G type specific oligonucleotides compared to 146 (58%; 99% Cl = 50-66%) that were typeable by MEIA. Forty-five (82%) of 55 stools containing G type 1, 80 of 84 (95%) containing G type 2, 0 of 3 containing G type 3, and 2 of 4 (50%) containing G type 4 as identified by MEIA hybridized with G type specific oligonucleotides. Differences in nucleotide sequences coding for VP7, in addition to destruction of the VP7 antigen by freezing and thawing of the specimen, may explain why not all rotavirus hybridized with G type specific probes.

Attenuated Vibrio cholerae oral vaccine CVD 103-HgR was well tolerated by 324 Thai soldiers and civilians. Most received a single 5 x 10(8) cfu dose, while 40 each received one or two 5 x 10(9) cfu doses. Vibriocidal antibody (the best correlate of immunity) seroconversion was lower in soldiers than civilians (P less than .001). Increasing the vaccine dose to 5 x 10(9) cfu raised the geometric mean titer (P less than .001). A second 5 x 10(9) cfu dose one week later did not notably increase seroconversions. Likelihood of seroconversion was inversely correlated with baseline vibriocidal titer (P less than .001). CVD 103-HgR caused seroconversion in most subjects with baseline titers less than or equal to 1:40, including 100% of civilians after one 5 x 10(8) cfu dose, 79% of soldiers after one 5 x 10(9) cfu dose, and 45% of soldiers after one 5 x 10(8) cfu dose. In persons with elevated baseline titers, vibriocidal antibody seroconversion is not a sensitive measure of whether vaccine has boosted intestinal immunity; for such subjects, other measurements must be used. Study regimens in endemic areas should use a single 5 x 10(9) cfu dose.

A synthetic oligonucleotide probe was developed to identify the gene for the heat-stable enterotoxin (NAG-ST) of non-serovar O1 Vibrio cholerae. Of 103 non-O1 V. cholerae isolates from Thailand, 31 isolates from Mexico, and 47 isolates from patients in the United States, only 7 (all from Thailand) hybridized with the probe. Probe-positive strains produced significantly higher fluid accumulations in infant mice than probe-negative strains.

SUMMARYVibrio cholerae O139 first appeared in India and Bangladesh in 1992. Surveillance for O139 was started at three hospitals in Thailand in 1993. By 1994 all three hospitals surveyed in Thailand had experienced an increase in Vibrio cholerae O139 infections.

We examined isolates from 203 sporadic and outbreak-associated Salmonella enteritidis cases occurring in Maryland between 1985 and 1990. Plasmid profiles were determined for all isolates; 52 isolates were phage typed. Ten plasmid profiles were identified. A single profile (consisting of a single ca. 55-kb plasmid) emerged as the predominant profile in Maryland during the study period. This profile (which was closely associated with phage type 8) accounted for 86% of a group of isolates from sporadic cases in 1988 and 1989, compared with 43% of the 1985 isolates. Strains with this profile were identified in four of nine outbreaks, including one of three outbreaks in which eggs were implicated as a vehicle. While plasmid profiles and phage typing appear to provide complementary means of identifying specific strains of S. enteritidis, the emergence of what appears to be a single predominant clone has reduced the discriminant ability of both typing systems. The factors be a single predominant clone has reduced the discriminant ability of both typing systems. The factors contributing to the emergence of this one clone are still not well understood.

To determine the etiology of diarrhea among expatriate residents living in a developing country and identify risk factors for travelers' diarrhea that are difficult to evaluate in tourist populations.Clinic based case-control study.Primary care travel medicine clinic in Kathmandu, Nepal.A total of 69 expatriate residents with diarrhea, compared with 120 tourists with diarrhea, and 112 asymptomatic resident and tourist controls, selected systematically during a 1-year period.Risk factors for diarrhea assessed by questionnaire and pathogen prevalence assessed by microbiologic analysis of stool specimens.The dominant risk factors for diarrhea among expatriate residents included younger age (P = .003), shorter duration of stay in Nepal (P.001), and eating out in restaurants (P = .01). Eating raw vegetables, salads, fresh fruit, or ice served in restaurants was not significantly associated with diarrhea. Longer duration of residence was linearly correlated with protection. Enteric pathogens were identified in 44 (64%) of 69 residents with diarrhea compared with 100 (83%) of 120 tourists with diarrhea, with enterotoxigenic Escherichia coli, Campylobacter, and Shigella predominant for both groups. Pathogens were also found in stools from 32 (37%) of 87 asymptomatic resident controls and 13 (52%) of 25 tourist controls. The attack rate of diarrhea among expatriates was estimated to be 49% (95% confidence interval, 37% to 61%) per month during the first 2 years of residence. The highest-risk months were April through July.Diarrhea among expatriates in a highly endemic environment is a persistent risk. The extremely high prevalence of enteric pathogens among asymptomatic persons reflects widespread exposure. The most important risk factors for travellers' diarrhea are difficult to modify, including younger age, duration of stay, eating in restaurants, and seasonality. Preventive dietary recommendations may not be fully protective, suggesting that pretravel advice should emphasize empiric treatment in addition to strategies to avoid exposure.

The rate of detection of Shigella and enteroinvasive Escherichia coli (EIEC) using a PCR technique was compared with the rate detected by standard microbiological methods (bacteriology plus hybridization of E. coli colonies with a 17 kb EIEC probe) among patients with dysentery before and after antibiotic therapy. The PCR amplified DNA sequences encoding IpaH, a multiple copy sequence located on the chromosome and the invasion plasmid. Shigella or EIEC were detected using the IpaH PCR system among 72 (61%) of 119 patients with dysentery on the first day they were seen at hospital, compared to 50 (42%) using standard microbiological methods (p = 0.006). After three days of antibiotic therapy, IpaH sequences were detected in stools from 38 percent of patients, compared to 10 percent using standard microbiology (p0.001). After seven days of therapy, the rates were 26 percent vs. 8 percent respectively (p0.001). The IpaH PCR system appeared to be specific for Shigella or EIEC based on low rates of positive reactions among non-diarrhoea controls, and a strong correlation between persistently positive reactions and antibiotic resistance of bacterial isolates. IpaH sequences were detected in 10 (8%) of 119 drinking water samples from homes of patients with disease; none of these specimens were positive for Shigella or EIEC by standard microbiology. In conclusion, PCR amplification of IpaH sequences and detection of target DNA with a non-radioactive probe increased the rates of identification of Shigella and EIEC by 45% in initial clinical specimens and by nearly 300% in specimens obtained from patients receiving antibiotic therapy.

An epidemic of a cholera-like disease occurred among Khmers in a camp in Aranyaprathet, Thailand, in May 1990. Of 215 patients with diarrhea, Vibrio cholerae O1 was isolated from 25 (12%) and V. cholerae non-O1 was isolated from 15 (7%). Five of 15 (33%) non-O1 V. cholerae isolates hybridized with two different oligonucleotide probes previously used to detect V. cholerae non-O1 that produces a heat-stable toxin. This is the first description of an epidemic of diarrhea caused by V. cholerae non-O1 that produces heat-stable toxin.

Ninety-five (28%) of 333 U.S. military personnel deployed to Ubonratchathani, Thailand, for 1 month in February 1993 developed diarrhea. Campylobacter jejuni was identified in 6 (25%), attaching and effacing Escherichia coli was identified in 3 (13%), nontyphoidal Salmonella spp. were identified in 2 (8%), and rotavirus was identified in 1 (4%) of 24 persons who had diarrhea and submitted specimens.

The clinical and epidemiologic features of vibrio infections occurring over 15 y in a hospital adjacent to the Chesapeake Bay were examined. Microbiologic techniques included the use of thiosulfate citrate bile salts sucrose (TCBS) medium on all stool specimens. Among 40 vibrio isolates from 32 patients, eight species were identified: V. parahaemolyticus (16), V. vulnificus (10), non-O1 V. cholerae (7), V. mimicus (3), V. hollisae (1), V. fluvialis (1), V. alginolyticus (1), and an unnamed halophilic vibrio. Sources included stool (13), wound (11), sputum (3), ear (3), bone (1), and gallbladder (1). While illnesses were diverse, they were relatively mild and self-limited with no mortality. The mild clinical spectrum and especially lack of mortality are in sharp contrast to the findings of previous reports. Even with the proximity to the bay and use of optimal isolation techniques, the demonstrated incidence of vibrio infections was low (1.6/100,000/y). The routine use of TCBS medium, which has been advocated for high-risk areas, was not cost-effective.