Potential sources of enterotoxigenic Escherichia coli in homes of children with diarrhoea in Thailand.

PIP: A year-long study was performed to identify potential sources of enterotoxigenic Escherichia coli (ETEC) within the homes of children with diarrhea in Bangkok. ETEC was identified in 8% (10 of 130) of the inhabitants of 42 homes with children with ETEC diarrhea and 6% (8 of 137) of their neighbors, but in only 2% (49 of 3077) of those individuals living in 866 homes not associated with children with ETEC diarrhea. While 46% (13 of 28) of the children under age 2 infected with ETEC were identified on home visits as having had a recent history of diarrhea, only 13% (5 of 39) of those over age 2 presented such a history. ETEC was isolated from 14% of the mothers' hands, 13% of the children's hands, and 7% of jars containing bath water that was used for washing the children after defecation. Drinking water was identified as a probable source of infection in 1 of 42 cases. Further studies are needed to determine whether ETEC from water stored in the home can spread and cause secondary infections.^ieng

Escherichia coli contains plasmids coding for heat-stable b, other enterotoxins, and antibiotic resistance.

Plasmid DNAs obtained from 18 Escherichia coli isolates that hybridized with the heat-stable b (ST-b) enterotoxin gene probe were examined by Southern blot analysis for genes coding for heat-labile, ST-a, and ST-b enterotoxins with specific radiolabeled DNA probes. Four E. coli isolates contained plasmids coding for both heat-labile and ST-b enterotoxins, and one isolate contained a plasmid coding for ST-a and ST-b. Five of 11 isolates of antibiotic-resistant enterotoxigenic E. coli isolates containing ST-b-coding DNA transferred a plasmid coding for both antibiotic resistance and ST-b to E. coli K-12, suggesting that the widespread use of antibiotics could increase the distribution of genes coding for ST-b.

A comparative study of enterotoxigenic Escherichia coli, Shigella, Aeromonas, and Vibrio as etiologies of diarrhea in northeastern Thailand.

The incidence of enterotoxigenic Escherichia coli (ETEC), Shigella, Aeromonas, and Vibrio was determined in patients with diarrhea seen at a hospital in northeastern Thailand, and compared with the incidence of these bacteria in household contacts and their neighbors. ETEC was identified in 17%, Shigella in 9%, Aeromonas in 9%, V. parahaemolyticus in 5%, and non-01 V. cholerae in 2% of 299 patients with diarrhea. These five species of bacteria were isolated more often from patients with diarrhea than persons without diarrhea (P less than 0.001). ETEC was found more often in household contacts (22/141) and neighbors (18/147) of index cases than in persons living in homes not associated with ETEC infections (32/1,318; P less than 0.001). While Shigella was isolated less often in family contacts (3/76) and neighbors (4/93) of patients with shigellosis, this enteric pathogen was also isolated more often from contacts than persons not associated with Shigella infection (13/1,437; P less than 0.001). Both Aeromonas and non-01 V. cholerae can also be enteric pathogens; further efforts should be made to define the enteropathogenicity of these bacteria.

Non-O1 Vibrio cholerae in Thailand: homology with cloned cholera toxin genes.

We examined 281 non-O1 Vibrio cholerae isolates from Thailand for homology with genes coding for cholera toxin. Five isolates from environmental sources were homologous with the cholera toxin gene probe and produced both the A and B subunits of cholera toxin.

Identification by DNA hybridization of enterotoxigenic Escherichia coli in a longitudinal study of villages in Thailand.

Radioactively labeled enterotoxin genes were used to study the epidemiology of enterotoxigenic Escherichia coli infections in two Thai villages. When E. coli that were isolated from 674 specimens were fixed on nitrocellulose paper and examined for hybridization with E. coli enterotoxin gene probes in Bangkok, the technique had a sensitivity of 94% (31 of 33) and a specificity of 100% (641 of 641), when compared with tests of E. coli for enterotoxin production in the Y-1-adrenal cell and suckling-mouse assays. However, when the same specimens were fixed directly onto nitrocellulose paper at a field laboratory and transported to the reference laboratory for assay with the gene probes, 27 specimens that contained enterotoxigenic E. coli did not hybridize with the E. coli gene probes. Enterotoxigenic E. coli that hybridized with the LT, ST-H, and ST-P probes were identified in 10% (17 of 177) of villagers with diarrhea, 7% (8 of 108) of contacts of individuals with diarrhea caused by enterotoxigenic E. coli, and 3% (32 of 1,199) of persons not associated with cases of diarrhea caused by enterotoxigenic E. coli. Enterotoxigenic E. coli that hybridized with the ST-II probe was not a cause of diarrhea. Alternative methods of retaining DNA on filters under field conditions are needed before this technique can be used for direct examination of specimens with enterotoxin gene probes.

Colonization factors associated with enterotoxigenic Escherichia coli isolated in Thailand.

Eighty-six percent (72 of 84) of heat-labile and heat-stable, none of 141 heat-labile, and 24% (27 of 111) heat-stable enterotoxigenic Escherichia coli isolates from Thailand aggregated in less than 1 M (NH4)2SO4, hemagglutinated human group A and bovine erythrocytes in 1% D-mannose, and possessed either colonization factor I or colonization factor II. No other colonization factors were identified by these two methods.

Identification by DNA hybridisation of enterotoxigenic Escherichia coli in homes of children with diarrhoea.

The DNA hybridisation technique to detect genes coding for Escherichia coli enterotoxin was used to identify enterotoxigenic E coli (ETEC) in homes of children with diarrhoea in Thailand. ETEC was found in 30 (14%) of 221 children with diarrhoea and in 9% (8/88) of their household contacts, 8% (8/101) of their neighbours, and 2% (32/1379) of inhabitants of 382 homes not associated with ETEC infections. ETEC was found significantly more often in water and food and on mothers' hands in homes of children with ETEC-associated diarrhoea and of their neighbours than in homes of children without ETEC infections (8/360 vs 3/2290; p less than 0.001). ETEC was identified in 80% (71/89) of specimens that hybridised with the enterotoxin gene probes by testing E coli isolated from the same specimen in the Y-1 adrenal and suckling-mouse assays. The DNA hybridisation assay to detect genes coding for E coli enterotoxin is an effective method of identifying ETEC in a large number of human and environmental specimens and will be a valuable tool to define further the epidemiology of this enteric pathogen.

Flies as a source of enteric pathogens in a rural village in Thailand.

The village of Ban Pong in northeastern Thailand was studied from January through December 1981 to determine the importance of flies as a source of enteric pathogens. The number of flies (predominantly Musca domestica) increased in kitchens and animal pens in the hot dry spring, when the incidence of diarrhea was highest in the village. Enterotoxigenic Escherichia coli, Shigella spp., non-O1 Vibrio cholerae, and Vibrio fluvalis were isolated from fly pools in yards (69%), animal pens (38%), bathrooms (35%), and kitchens (8%). Enterotoxigenic E. coli was isolated from one fly pool in May and from another in June, when the incidence of such infections was highest in the village. Flies often carry and presumably disseminate enteric pathogens in rural Thailand.

Detection of enterotoxigenic Escherichia coli in water by filter hybridization with three enterotoxin gene probes.

The DNA hybridization assay for genes encoding for Escherichia coli enterotoxins was used to examine water specimens in Thailand. In a reconstruction experiment, the DNA hybridization assay was 10(4) times more sensitive than testing random E. coli in the Y-1 adrenal and suckling mouse assays in identifying enterotoxigenic E. coli (ETEC) in water. Drinking and bathing water collected from 2 of 10 different homes of individuals with ETEC-associated diarrhea and 6% (5 of 78) and 11% (11 of 78) of drinking and bathing water samples collected from homes of individuals with diarrhea without ETEC infections, as well as 6% (5 of 77) and 8% (6 of 77) of drinking and bathing water collected from homes in which no inhabitants had diarrhea, were homologous with the DNA probes. Ten E. coli from each of the 31 water specimens which contained bacteria which were homologous with the DNA probes were tested in the Y-1 adrenal and suckling mouse assay. In only 2 of these 31 specimens could ETEC be identified with the standard assays. The DNA hybridization assay is a much more sensitive means of detecting organisms carrying genes coding for enterotoxin production than testing 10 individual colonies in the Y-1 adrenal and suckling mouse assays. This novel application of recombinant DNA technology provides a sensitive method of detecting organisms carrying genes coding for enterotoxin, and this method will be useful in defining the epidemiology of ETEC.

Identification of enterotoxigenic Escherichia coli by colony hybridization using three enterotoxin gene probes.

The applicability of examining clinical specimens with a DNA hybridization technique for genes encoding enterotoxins was examined using enterotoxigenic Escherichia coli (ETEC) that produced both heat-labile toxin (LT) and heat-stable toxin (ST) (24 isolates), ETEC that produced LT only (17 isolates), and ETEC that produced ST only (22 isolates) from Thailand. ETEC was identified with Y-l adrenal cell and suckling mouse assays. All were homologous with radiolabeled fragments of DNA encoding LT or ST of porcine origin (ST-P) or of human origin (ST-H). Strains of ETEC that produced ST only from rural Thailand were homologous with the ST-H probe only, whereas strains isolated in Bangkok were homologous with the ST-H probe, the ST-P probe, or both probes. The hybridization technique detected ETEC in all stool samples of patients with diarrhea from whom ETEC was isolated and in ETEC-inoculated water containing other species of bacteria. The DNA hybridization assay is useful for characterizing and identifying environmental sources of ETEC.

Epidemiologic study of risk factors in cancer of the cervix uteri in Thai women.

PIP: A case control study was conducted to identify various environmental factors associated with cervical cancer and the extent or degree of association of those factors with the disease. The cases were 212 histologically confirmed cervical cancer patients admitted to the gynecological ward in 4 Thailand hospitals. The controls were 212 patients diagnosed with other gynecological conditions except cancer (confirmed by pelvic examination and papanicolaou smear) who were admitted to those hospitals during the same period as the cases. The cases and controls were matched by age, using 5 year intervals. Questionnaires containing information such as sociodemographic data, marital status, pregnancy and delivery history, past history of illness, especially with genital tract infections, and husband's illness history including venereal diseases were distributed. Questionnaires were the same for case and control. Cases and controls were similar in demographic and social characteristics. All cases were younger at 1st intercourse and had a higher number of pregnancies and parity than controls. Various factors presented significantly more in the cases than the controls. The suspected risk factors in cervical cancer were: parity, with cases showing higher parity than control; positive history of vaginal infections; higher number of marriages; younger age at 1st intercourse and history of husband's sexually transmitted disease. Circumcision in the husband indicated a protective factor to this disease, although the number of husbands who had circumcision in this study were very few. The risk factor of highest relative risk value was the marriage factor, followed by factors of high parity. Women who had 3 or more live births were 3 times more prone to cervical cancer than women with lower fertility. Women who had multiple marriages also ran a higher risk to this disease, as did those who had history of vaginal infection and husband's history of sexually transmitted disease. Women with a history of irregular menstruation both of amount and frequency were twice as prone to cervical cancer than normal women. The degree of association between risk factors and cervical cancer as expressed by odd ration was shown by various combinations of the risk factors, such as high parity and positive history of vaginal infection. These 2 characteristics were about 9 times more prone to cervical cancer than women without these characteristics. Women with 4 risk factors combined had the greatest risk compared to those who did not have those factors.^ieng

Enteropathogenicity of Aeromonas hydrophila and Plesiomonas shigelloides: prevalence among individuals with and without diarrhea in Thailand.

To evaluate the enteropathogenicity of Aeromonas hydrophila and Plesiomonas shigelloides, the rate of isolation of these organisms was compared among individuals with and without diarrhea in Thailand. In two groups of American travelers, A. hydrophila, but not P. shigelloides, was associated with episodes of travelers diarrhea more often than when individuals did not have diarrhea (P less than 0.025). Among three populations of Thais, A. hydrophila and P. shigelloides were isolated with similar frequencies from individuals with and without diarrhea. The biochemical characteristics, production of cytotoxin, and ability to distend suckling mouse intestine were similar among A. hydrophila isolates from individuals with and without diarrhea. However, cytotoxic A. hydrophila strains distended rabbit and suckling mouse intestine and produced destructive lesions in intestinal mucosa of both species of animal. P. shigelloides strains produced neither cytotoxin nor distended intestine. Oral administration of whole cultures (10(9)) of cytotoxic A. hydrophila or P. shigelloides failed to cause diarrhea in rhesus monkeys. Volunteer studies or intestinal biopsies of patients with diarrhea may be required to establish whether A. hydrophila is a gastrointestinal pathogen in humans.