Molecular Epidemiological Study of Outbreaks of Shigella sonnei infection between 1995 – 2003 in Taiwan
2005 Vol.21 NO.10
Shigella sonnei, the most common intestinal and diarrhea-inducing pathogen in Taiwan, often results in major infection clusters or outbreaks. In this study, we use three genotyping methods including M13 arbitrary primer polymerase chain reaction (AP-PCR), plasmid profile assay (PPA), and pulsed-field gel electrophoresis (PFGE) to analyze the molecular relationship between strains of Shigella sonnei outbreaks during the years 1995 – 2003 in Taiwan. Of the six strains isolated from Shigella sonnei outbreaks, the results of Xba I and Sfi I PFGE showed that they could be separated into six subtypes (X-I ~ VI, S1 - S6). The dendrogram indices (DI) among strains were between 0.25 and 0.65. Their plasmid profiles could also be separated into seven subtypes (P1 - P7). Comparing each outbreak with the seven molecular types (X1 - X6) isolated in northern Taiwan in 2001, the strains from a kindergarten in I-lan (X-I) and an elementary school in Ping-Chen, Tao-Yuan were closely related to X2 and X3 strains in Northern Taiwan. The outbreak in a Hualien Senior High School in eastern Taiwan was closely related to local sporadic cases, and had greater differences from the strains in northern Taiwan. Outbreaks in Mountain A-Li and Ba-li Island (X-IV and X-VI) were significantly different from that in northern Taiwan. The outbreak in Dan-Shuei had 93% homology with the strain in metropolitan Taipei, suggesting its cause to be by regional water contamination.