A prospective study on Shiga toxin-producing Escherichia coli in children with diarrhoea in Parana State, Brazil

To examine stool specimens from children with diarrhea from Parana State, southern Brazil, for presence of STEC. A PCR screening assay for stx genes was used to examine a loopful of confluent colonies of 306 stool samples cultures. In six (1.96%) of them, DNA fragments of the expected size were observed, and the presence of stx was confirmed by DNA sequencing. Then up to 100 single colonies from each of the six stool cultures were analyzed using the same PCR protocol. However, stx-positive colonies were found only in two of the cultures. The E. coli strains belonged to serotypes O69:H11 and O178:H19, and presented genotypes stx(1)eae ehxA and stx(1) respectively. Shiga toxin production was confirmed using the VTEC Screen Seiken. Except ampicillin, they were susceptible to all the antimicrobials tested. These results show that STEC may be an important cause of diarrhea in children of Parana State, and that they are present in low numbers in stools. The strains belonged to serotypes not commonly found associated with STEC and probably present low virulence. These results indicate that molecular methods are required to diagnosis of STEC infections.