Molecular epidemiological study on emerging enteric infections in Asia

采用脉冲场凝胶电泳（PFGE）方法对泰国和越南分离的副溶血性弧菌大流行新毒株的DNA指纹图谱进行了研究。结果表明，在泰国的感染主要是由寄生于双壳类软体动物的菌株引起的，并且O3:K6血清型明显转变为O1:K25血清型等。发生在越南。对代表亚洲各国分离株的60株大流行毒株的11个基因的核苷酸序列进行了组合分析。结果表明，O3:K6、O4:K68和O1:KUT毒株存在系统亲缘关系，可能是大流行毒株的祖先毒株。从马来西亚海产品中分离的20株ctx^+霍乱弧菌中有15株属于新的血清型（O139）。这些菌株和从印度和孟加拉国以及从国际旅行者中分离的ctx^+霍乱弧菌菌株进行了pfge树状图分析。这些菌株之间的系统发育关系表明，马来西亚的O139菌株是在两个不同的场合从孟加拉地区传入的。采用多位点序列分型方法对包括上述菌株在内的79株霍乱弧菌5个基因的核苷酸序列进行了测定和分析。结果支持PFGE方法得到的菌株的系统发育关系。我们对大肠杆菌O157的研究表明该菌在亚洲环境中广泛分布。然而，相当数量的环境菌株产生很少的Stx2。这至少部分是由于Q基因周围的DNA序列发生了变化。这种基因变化与在亚洲国家很少报告感染大肠杆菌O157的患者这一事实似乎是相关的。

We studied the DNA fingerprints of new pandemic strains of Vibrio parahaemolyticus isolated in Thailand and Vietnam by using the pulsed field gel electrophoresis(PFGE) method. The results indicated that strains harbored in molluscan bivalves are responsible for infection in Thailand and that clear transition of O3:K6 serotype to O1:K25,etc. occurred in Vietnam. The nucleotide sequences of 11 genes in 60 pandemic strains representing the isolates in various Asian countries were combined and analyzed. The result indicated that O3:K6,O4:K68, and O1:KUT strains are phylogenetically related and possible ancestral strains of the pandemic strains were found.Of the 20 ctx^+ Vibrio cholerae strains isolated from the seafoods in Malaysia 15 strains belonged to the new serotype (O139). These strains and ctx^+ V.cholerae strains isolated in India and Bangladesh and from international travelers were subjected to the PFGE-dendrogram analysis. The phylogenetic relationship among these strains suggested that Malaysian O139 strains were introduced from the Bengal area in two separate occasions. The nucleotide sequences of five genes of 79 strains of V.cholerae including the above strains were determined and analyzed by a multilocus sequence typing approach. The result supported the phylogenetic relationship of the strains obtained by the PFGE method.Our study on Escherichia coli O157 suggested this organism is widely distributed in Asian environment. However, considerable number of the environmental strains produced very little amount of Stx2. This was due at least in part to the change in the DNA sequence around the Q gene. This genetic change and the fact that very few patients infected by E.coli O157 are reported in Asian countries appear to be related.