Detection of heat-stable enterotoxigenic Escherichia coli by hybridization with an RNA transcript probe.

Heat-stable enterotoxigenic Escherichia coli was identified by nucleotide hybridization with RNA transcripts of the gene encoding heat-stable A-2 enterotoxin. Radiolabeled enterotoxin gene RNA transcripts are easier to prepare and avoid the preparation of cloned DNA probes that can be nonspecific if they contain cloning vector DNA.

Prevalence of heat-stable II enterotoxigenic Escherichia coli in pigs, water, and people at farms in Thailand as determined by DNA hybridization.

The DNA hybridization assay employing a 460-base-pair fragment of DNA encoding for the methanol-insoluble form of heat-stable toxin (ST-II) was used to determine the prevalence of ST-II enterotoxigenic Escherichia coli (ETEC) in pigs, people, and water at 57 farms in Sri Racha, Thailand. ST-II ETEC was found in 62 (3%) of 2,110 suckling, 181 (32%) of 560 weaned, and 4 (1%) of 457 adult pigs examined. Of 62 suckling pigs with ST-II ETEC infections 21% had diarrhea, but none of 185 infected older pigs had diarrhea. ST-II ETEC was found more frequently in suckling pigs with diarrhea than without diarrhea (13 of 146 versus 49 of 1,964) (P less than 0.001). ST-II ETEC was detected in water collected from 3 of 57 clay jars containing water used to bathe at three pig farms, in 1 jar used to bathe immediately after working in the barn, and from one farmer who did not have a recent history of diarrhea. Evidence of this organism was not found in 245 other individuals living on the pig farms or in 220 inhabitants and 114 water specimens collected at tapioca farms nearby. In Thailand ST-II ETEC was found in suckling pigs with diarrhea but was infrequently found in humans.

Infection rates of respiratory syncytial virus in pediatric patients attending Phra Mongkutklao Hospital, Bangkok.

Respiratory syncytial virus (RSV) and other pathogens were isolated from nasopharyngeal secretions from 200 pediatric patients attending the Out Patient Department of Phra Mongkutklao Hospital with symptoms of upper respiratory tract infections. Their sera were also taken for determination of class specific immunoglobulin antibody titers. The positive isolation rates were 36% for RSV, 5.5% for adenovirus 1.5% for herpes simplex virus (HSV), and 4% for Staphylococcus aureus. One to 5.5% of these patients had mixed infection. Ninety five percent of patients with positive RSV isolations had IgM antibody which was found only in 30.7% in patients with negative RSV isolations. This result indicated that RSV was likely to be the most common pathogen responsible for the upper respiratory tract infections in children in Bangkok during the rainy season.

Herpes simplex virus and genital infections in Thai pregnant women.

Vaginal swabs were collected monthly from 100 asymptomatic Thai pregnant women as well as from 11 pregnant women with herpetic lesions of the vulva for isolations of HVH, mycoplasma and gonorrhoea. In asymptomatic mothers, 25% and 21% of cases were positive for HVH and mycoplasma respectively. Mixed infections of HVH and mycoplasma, and HVH and gonorrhoea were also found in 27% and 1% of cases respectively. Follow-up in asymptomatic pregnant women and those with herpetic lesions showed positive HVH fluctuations throughout the course of study. Positive HVH was recovered from 48% of amniotic fluid and 32% of breast milk of asymptomatic pregnant women with positive HVH genital isolates, and in 72.7% of aminotic fluid and 36.4% of breast milk in patients with herpetic lesions. HVH was also isolated from 84% of infants of asymptomatic mothers positive for HVH, and 100% of patients with herpetic ulcer. HVH was isolated most frequently from the throat and also from nose, eyes, and ears but with less frequency. IgM antibodies were found in three infants born of asymptomatic mother and in one infant of a mother with herpetic lesion. The low percentage of IgM antibody was interpreted to mean that the HVH isolated from the newborn infants were acquired during passage through the birth canal.

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.