Analysis of the molecular biologic characterization of Shigella flexneri 4c isolates

Objective To analysis the molecular biological characteristics of Shigella flexneri 4c isolates from patients of shigellosis outbreak and sporadic diaxrbea in Hangzhou during 2003-2007. Method 24 S. flexneri 4c isolates were identified by biochemical tests and serotyping. Among these isolates, invasive plasmid antigen H gene (ipaH) was examined by PCR, and molecular typing was performed by Pulse-field gel electrophoresis(PFGE). Results All 24 isolates were serotyped as S. flexneri 4c and were positive for ipaH gene. A total of 17 different PFGE patterns were identified among these 24 isolates with Dice coefficient varying from 0.71 to 1.00. On the basis of PFGE patterns, S. flexneri 4c isolates from each of three shigellesis outbreaks were closely related. Some isolates from three outbreaks (outbreak in 2005,2006 and 2003 year which named as outbreak 1,2,3 respectively) were possibly related (Dice coefficient > 0.8). The sporadic isolates were demonstrated to be distinct from the isolates from two outbreaks (outbreak 1,3) ( Dice coefficient 0.8). Conclusions All S. flexneri 4c in Hangzhou possess ipaH. The S. flexneri 4c isolates from three recent outbreaks in Hangzhou may belong to the same clone. Key words: Shigella;  4c subtype;  ipaH;  Pulse-field gel electrophoresis;  Typing