志贺菌属编码赖氨酸的基因簇缺失情况分析

Deletion of gene cluster encoding lysine decarboxylase of Escherichia coli in Shigella species

目的 探讨编码赖氨酸利用的cadABC基因簇的缺失在志贺菌中的普遍性。方法 根据大肠杆菌K 12MG16 5 5菌株的cadABC基因簇序列设计引物 ,使用PCR和核酸杂交试验检测。结果在志贺菌的 4个群 4 2个血清型 4 3株菌中 ,均发生了cadABC基因簇的缺失。其中 2 9(6 7.4 % )株菌发生了cadABC基因簇的全部缺失 ,主要表现在A群和C群。A群的 12个血清型中有 10个发生了完全缺失 ,C群的 18个血清型中有 16个发生了完全缺失。其余 13个血清型中的 14株菌发生了部分缺失或重组。不完全缺失主要发生在B群 ,B群的 11个血清型中的 8个表现为部分缺失。D群的 2个菌株和肠侵袭性大肠杆菌的 2个菌株全部表现出部分缺失 ,但缺失的程度不同。结论 在志贺菌属的 4个群 4 2个血清型中 ,全部发生了cadABC基因簇的缺失 ,表现为完全缺失和部分缺失。结果提示 ,志贺菌的进化可能和cadABC基因簇的缺失有关。

Objective To study the prevalence of the gene cluster encoding lysine decarboxylase (cadABC) of Escherichia coli in Shigella species. Methods DNA hybridization and PCR were used in this study with the primers designed according to the cadABC sequence of E.coli K-12 MG1655. Results In total 43 strains of 42 serotypes of Shigella species examined that do not metabolize lysine, complete deletion of cadABC gene cluster was found in 29(67.4% ) strains, including 10 of 12 serotypes of group A, 3 of 11 serotypes of group B and 16 of 18 serotypes of group C. The partial deletion of the cad gene cluster was observed in the rest of the isolates including 8 of 11 serotypes of group B. Conclusion The cadABC gene cluster was universily deleted in all of the 42 serotypes of Shigella species and enteroinvasive E.coli , including complete and partial deletion. This observation indicated that the cadABC deletion involved in the evolutionary process of Shigella species from E.coli .