A study was done to explore the presence of Shiga toxin-producing Escherichia coli (STEC) from diarrhoeal children in the pastoral systems of Kiruhura district in south-western Uganda and to investigate the serogroups, Shiga-toxin production and carriage of eae genes by STEC strains. Of the 256 faecal samples, E. coli was isolated from 86.7% of the children. PCR assays for the detection of stx genes carried out on a sweep of E. coli colonies detected STEC in 18 isolates. Of the 180 individual colonies screened, 45% were stx-positive colonies; of these 37% and 32.1% contained stx1 and stx2 alone, respectively, while 30.9% contained both stx genes. The genetic profile of intra-host STEC clones was determined using PFGE. In 13 children infected with multiple STEC isolates, 5 children were each co-infected by multiple clones. In each of remaining 8 children infection was by a single clone of STEC. Nineteen of the 25 sero-typed strains expressed O antigens and segregated into 15 O sero-groups. Significantly, pathogenic serogroups O8, O74, O78, O76, O111, O113 and clones such as O29, O149 and O176 which have not been described as human pathogens were detected. eae gene was detected in 15 of 25 strains and a majority of strains (80%) that belonged to different sero-groups produced Stx1, Stx2 or both toxins. None of the children were co-infected with STEC and Salmonella or Shigella species. The presence of pathogenic sero-groups suggested that STEC may be an emerging pathogen among rural children in close contact with cattle in Uganda.
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