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Journal of Clinical Microbiology, November 2007, p. 3620-3625, Vol. 45, No. 11
0095-1137/07/$08.00+0     doi:10.1128/JCM.00596-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Comparison between O Serotyping Method and Multiplex Real-Time PCR To Identify Diarrheagenic Escherichia coli in Taiwan{triangledown}

Ji-Rong Yang,1 Fang-Tzy Wu,1 Jin-Lai Tsai,1 Jung-Jung Mu,1 Ling-Fen Lin,1 Kuang-Lo Chen,1 Steve Hsu-Sung Kuo,1 Chuen-Sheue Chiang,1,2* and Ho-Sheng Wu1,3*

Research and Diagnostic Center, Centers for Disease Control, Department of Health, Taipei, Taiwan,1 Center of General Education, National Taipei College of Nursing, Taipei, Taiwan,2 School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei, Taiwan3

Received 18 March 2007/ Returned for modification 24 July 2007/ Accepted 2 August 2007

To compare the diarrheagenic Escherichia coli (DEC) identifications obtained between traditional O serotyping and modern virulence gene detection assays, we developed a multiplex real-time PCR assay by detecting six specific virulence genes for enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), and enteroinvasive E. coli (EIEC). Among 261 clinical diarrheal stool samples, a total of 137 suspected DEC (sDEC) isolates were identified by the use of commercially available antisera. The most prevalent serogroups were O1 (12/137; 8.7%), O25 (9/137; 6.5%), and O44 (9/137; 6.5%). The specific virulence genes for the 137 sDEC isolates were analyzed by the multiplex real-time PCR assay. Fifteen (10.9%) of 137 isolates were confirmed to be true DEC strains, indicating that the serotypic markers did not correlate with the specific virulence genes. ETEC (66.7%) was the most prevalent, followed by EIEC (20%) and EPEC (13.3%). No EHEC strains were identified in the specimens. Four novel serotypes were found in the study: two in EPEC strains (O111:H9 and O63:H6) and two in EIEC strains (O63:H9 and O169:H9). In conclusion, the real-time PCR assay considerably reduces the high false-positive rate from the use of serotyping alone, and thus, it is suggested that serogrouping-based methods are inadequate for the identification of DEC isolates, although they are useful for the identification of a limited number of serogroups. In addition, ETEC, EPEC, and EIEC strains were present in 5.7% (15/261) of the diarrheal patients in northern Taiwan in 2006.

* Corresponding author. Mailing address for Ho-Sheng Wu: Research and Diagnostic Center, Centers for Disease Control, 161, Kunyang Street, Taipei 115, Taiwan. Phone: 886-2-26531377. Fax: 886-2-27837779. E-mail: wuhs{at}cdc.gov.tw. Mailing address for Chuen-Sheue Chiang: Research and Diagnostic Center, Centers for Disease Control, 161 Kunyang Street, Taipei 115, Taiwan. Phone: 886-2-26531355. Fax: 866-2-27864367. E-mail: cschiang10{at}cdc.gov.tw

{triangledown} Published ahead of print on 29 August 2007.

Journal of Clinical Microbiology, November 2007, p. 3620-3625, Vol. 45, No. 11
0095-1137/07/$08.00+0     doi:10.1128/JCM.00596-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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