The DNA colony hybridization assay was used to identify enterotoxigenic Escherichia coli among E. coli isolated from 803 swine with diarrhea at 10 farms in Thailand. Between 5 September and 8 December 1981, enterotoxigenic E. coli were identified in 40% of 58 litters of piglets under 10 days old and 17% of 29 litters between 10 and 21 days old with diarrhea at farms at four different locations in Thailand. All E. coli that hybridized with one or more of the three enterotoxin gene probes produced heat-labile or heat-stable toxin or both, as determined by testing culture supernatants in the Y1 adrenal and suckling mouse assays. The DNA colony hybridization technique is a specific method of identifying enterotoxigenic E. coli from swine and can be used to further characterize these enteric pathogens.
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.
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