Clinical and microbiologic features of Shigella and enteroinvasive Escherichia coli infections detected by DNA hybridization.

To determine the clinical and microbiologic features of Shigella and enteroinvasive Escherichia coli (EIEC) infections, we investigated 410 children with diarrhea and 410 control children without diarrhea who were seen at Children's Hospital, Bangkok, Thailand, from January to June 1985. Shigella spp. were isolated from 96 (23%) and EIEC were isolated from 17 (4%) of 410 children with diarrhea and from 12 (3%) and 6 (1%) of 410 control children, respectively. The isolation rates of both pathogens increased with age and peaked in children 3 to 5 years old from whom Shigella spp. were isolated from 38% and EIEC were isolated from 9%. Shigella spp. were isolated from 52% and EIEC were isolated from 7% of 91 children with bloody diarrhea and from 15 and 3% of 319 children with nonbloody diarrhea. Fifteen (65%) of 23 EIEC were lactose positive, and all belonged to recognized EIEC serotypes. Among children with diarrhea, the stool blots of 76% of 17 children infected with EIEC, 45% of 96 children infected with Shigella spp., and 1% of 297 culture-negative children hybridized with the 17-kilobase EcoRI digestion fragment of pRM17, a recombinant plasmid containing DNA derived from the 140-megadalton Shigella flexneri plasmid. Although EIEC colonies can be reliably detected by DNA hybridization, detection by stool blot is less sensitive. Shigella spp. and EIEC are important causes of endemic diarrhea among children greater than 1 year old in Thailand.