Comparison of the Identification Methods of Diarrheagenic E. coli in Taiwan by O Serotyping and Single-tube

Ji-Rong Yang

2008 Vol.24 NO.9

Correspondence Author: Ji-Rong Yang


Differentiation of the 5 major types of diarrheagenic E. coli [EHEC (enterohemorrhagic E. coli), ETEC (enterotoxigenic E. coli), EPEC (enteropathogenic E. coli), EIEC (enteroinvasive E. coli), and EaggEC (enteroaggregative E. coli)] is very difficult even with the tools available today. In order to improve the ability of the Centers for Disease Control (CDC) to detect these pathogenic bacteria, the Research and Diagnosis Center established a set of real-time PCR methods to rapidly identify the following 4 types: ETEC, EHEC, EPEC, and EIEC. Six types of virulent genes were chosen for examination; specifically, lt and st for ETEC, stx1 and stx2 for EHEC, eae for EPEC, and ipaH for EIEC. In addition, we compared results of the traditional serotyping method with real-time PCR and found the association between the virulent genes and specific serotypes. Among 137 suspected strains of diarrheagenic E. coli, 15 strains were confirmed to carry virulent genes by real-time PCR, including 10 strains of ETEC with st, 3 strains of EIEC with ipaH and 2 strains of EPEC with eae. The positive rate of virulent genes was 10.9%, indicating that this method could substantially reduce the high number of false positive results that occur when using traditional serotyping for identification. In addition, after reviewing the literature, our study is the first to discover 6 new strains, including 2 strains of ETEC (O15:H16 and O1:H6), 2 strains of EPEC (O111:H9 and O63:H6), and 2 strains of EIEC (O63:H9 and O169:H9).
Keyword: Diarrheagenic E. coli, real-time PCR, serotyping, virulence gene, diarrhea