Serotypes and pathogenicity of Escherichia coli isolated from healthy individuals, May 1997-January 1999 Saitama, Japan
(IASR 2000; 21:95-96)

Escherichia coli, which cause diarrhea, are classified as enteropathogenic E.coli (EPEC), enteroinvasive E.coli (EIEC), enterotoxigenic E.coli (ETEC), enterohemorrhagic E.coli (EHEC), and enteroaggregative E.coli (EaggEC) according to difference in pathogenic mechanism. In order to classify, pathogenesis should be examined, but most of laboratories check serotype. Asymptomatic healthy individuals may yield E.coli which presents agglutination with commercial serotype kit, however its trend has scarcely reported. This report summarizes serotype and pathogenesis of E.coli from healthy carriers.

During May 1997 to January 1999, 4,667 individuals including kindergarteners, pupils, students, food handlers, and others in Saitama Prefecture were examined. E.coli was isolated by DHL and SM agar plate. Three E.coli-like colonies were selected, and they were characterized biochemically. If those colonies are identified as E.coli, their serotype (O and H) and existence of LT, ST, and STX gene were examined. In addition, according to serotype, eaeA, invE, aggR, and astA genes were examined by PCR.

Of 4,667 individuals, 429 (9.2%) yielded E.coli, 10 presented two serotypes, thus 439 E.coli were isolated. Of 44 commercially identifiable O serotypes, 37 were identified, and 20 of 22 H serotypes were identified. In total 118 serotype combination were classified. The most frequent serotype was O1:H7 (77), followed by O18:H7 (50), O1:H12 (17), and O1:HUT (17). Targeted pathogenic genes were not detected from 50 EPEC O18:H7 isolated. Of 439 strains, 76 had the pathogenic genes. There was no isolate which had LT or invE genes. EHEC was isolated from 2 individuals (0.043%), and its serotypes were O157:H7 (VT1&2) and O119:H21 (VT1). ETEC was isolated from 2 individuals (0.043%), and its serotypes were identified as O25:H- (STIa) and OUT:H- (STIa).

These isolates from healthy individuals should be compared with those from patients.

Reported by Takayuki Kurazono, Marina Kon, Masanori Yamaguchi, and Yoko Ohzeki, Saitama Institute of Public Health; Ken-ichiro Ito, National Institute of Public Health

Correspondence: Takayuki Kurazono;
E-mail: saikin@f3.dion.ne.jp

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