福氏志贺菌gtrI基因突变导致的血清型回复转换

Serotype conversion due to gtrI gene dysfunctional mutation in Shigella flexneri serotype Y strains

目的研究携带O抗修饰基因gtr I的福氏志贺菌Y血清型菌株特征。方法采用血清型多重聚合酶链反应(PCR)分型方法检测携带gtr I基因但I型抗原表位阴性的福氏志贺菌Y血清型菌株,并对其gtr I基因簇进行序列分析,对其基因组进行脉冲场凝胶电泳(PFGE)分析。结果 5株福氏志贺菌基因组携带gtr I基因簇,但是I型抗血清凝集阴性,表现为Y血清型特征;测序发现这5株菌株中的gtr I基因均发生了功能失活性突变;PFGE分析显示这5株菌株与福氏志贺菌血清型1a菌株具有相同或相近的PFGE带谱。结论携带O抗修饰基因gtr I的福氏志贺菌Y血清型菌株来源于血清型1a。

Objective To characterize the Shigella flexneri serotype Y strains carrying dysfunctional gtr I gene.Methods Multiple-PCR was conducted to screen S. flexneri strains which carry gtr I gene within genomes,but have antigenic epitope I on cell surface. The gtr Ⅰ gene clusters in these candidates were sequenced. The genome DNA of these strains were analyzed with PFGE and compared with that of other strains. Results A total of 5 strains were found to carry gtr I gene cluster within genomes,but not to react with typing I antisera,presenting the characteristics of serotype Y. Sequencing analysis suggested that all the strains had dysfunctional mutation in the gtr I gene sequence. The PFGE patterns of the 5 strains were identified,which were similar to that of serotype 1a strains. Conclusion The five serotype Y strains which carried dysfunctional gtr I gene were originated from serotype 1a through gtr I gene mutation.