Use of Shigella flexneri ipaC and ipaH Gene Sequences for the General Identification of Shigella spp. and Enteroinvasive Escherichia coli.

摘要

We have previously shown that the invasion plasmid antigen (ipa) genes ipaB, ipaC, and ipaD can be used as specific nucleic acid probes for the identification of Shigella spp. and enteroinvasive Escherichia coli (EIEC). These genes, which synthesize major surface immunogens detected with human convalescent-phase sera, are clustered on an 8-kilobase (kb) region of the large (180- to 210-kb) invasion plasmid that is present in all virulent Shigella spp. and EIEC. Several genetic determinants located on this large plasmid have been shown to be necessary for triggering the invasion of i.e., endocytosis by) colonic epithelial cells. The ipa gene cluster constitutes one of these invasion-essential loci and resides near a region of the plasmid that is a hot spot for spontaneous deletions (10). Loss of the invasion plasmid or deletion of the small region encompassing the ipa genes, independent events which occur at a relatively high frequency renders the bacteria noninvasive and therefore avirulent. Therefore, in native bacterial strains, the presence of the ipa genes correlates with, but is not an absolute indicator of, virulence. (JES)