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Article in Japanese

Prevalence of virulence genes of diarrheagenic Escherichia coli in O-serotypable strains isolated from stool samples of children with sporadic diarrhea

Hideaki KIKUTA1), Mitsuko WAKUSHIMA2), Yoshikazu NISHIKAWA2)

Ten enterovirulence genes (stx1, stx2, eae, elt, est-p, est-h, astA, aggR, afaB, virB) of diarrheagenic Eschenchia coli (E. coli) were examined by polymerase chain reaction in 98 O-serotypable strains isolated from the stool samples of 347 children with sporadic diarrhea. Among the 98 strains, 16 (16.3%) were positive for at least one of the virulence genes, identified as the diarrheagenic E. coli (DEC) strain. Eight of the 16 strains were aggR-positive, 7 were eae-positive and 7 were astA-positive. Of the 7 astA-positive strains, 6 were aggR-positive and one carried only the astA gene. Eight strains (8.2%), 7 strains (7.1%) and 1 strain (1.0%) of the 98 strains were identified as enteroaggregative E. coli (EAEC), enteropathogenic E. coli (EPEC) and E. coli possessing EAEC heat-stable enterotoxin 1 (EAST1EC), respectively. Although O1 (27 strains; 27.6%), O74 (23 strains; 23.5%), and O18 (18 strains; 18.4%) were the most prevalent serogroups, they possessed no enterovirulence genes. The serogroups of EAEC were O111 (3 strains), O127a (2 strains), O25 (1 strain), O126 (1 strain), and O166 (1 strain). The serogroups of EPEC were O22 (2 strains), O6 (1 strain), O15 (1 strain), O25 (1 strain), O26 (1 strain), and O153 (1 strain). The serogroup of EAST1EC was O153 (1 strain). EAEC and EPEC are causative agents of sporadic diarrhea in children. Serotyping is inadequate for the identification of DEC, although it is useful for epidemiological analysis.

1) Pediatric Clinic, Touei Hospital
2) Osaka City University Graduate School of Human Life Science

Key words
Received July 11, 2013
Accepted August 28, 2013

25 (4):413─419,2014