Conversion ofShigella flexneriserotype 2a to serotype Y in a shigellosis patient due to a single amino acid substitution in the protein product of the bacterial glucosyltransferasegtrIIgene

Abstract

Conversion of serotype from 2a to Y was demonstrated with five Shigella flexneri isolates recovered from an infected patient. When introduced into the serotype Y isolate, the glucosyltransferase (gtr) II gene of the serotype 2a isolate is capable of inducing the conversion from serotype Y to 2a. In contrast, the gtrII of the serotype Y isolate lacks the capacity to change serotype, resulting from a CysCTyr substitution in its predicted protein sequence. The protein product of the gtrII gene was detected. This is the first report of serotype conversion of S. flexneri in humans, and successful detection of the protein product from a gtr gene.

Development of a Multiplex PCR Assay Targeting O-Antigen Modification Genes for Molecular Serotyping of Shigella flexneri

“…Each pair of primers obtained the predicted amplification product, which were 782 bp (wzx [1][2][3][4][5] ), 1,122 bp (gtrI), 518 bp (gtrIC), 1,272 bp (gtrII), 604 bp (oac), 378 bp (gtrIV), 905 bp (gtrV), and 425 bp (gtrX). The identity of each product was further confirmed by DNA sequencing.…”

“…Serotype Y strains carrying a defective gtrII gene have been reported previously. One case was an insertion sequence disruption of gtrII, while another was a single amino acid residual change leading to an inactive GtrII (5,14). The higher number of gtrII mutations found in serotype 2a and 2b S. flexneri strains may be due to a higher proportion of these serotypes in nature.…”

“…The amplicon sizes showed good separation on 1.5% agarose gels and when two different molecular markers were used, and each PCR product could be unambiguously identified by size. The expected products for reference strains were as follows: 1a (wzx [1][2][3][4][5] and gtrI), 1b (wzx [1][2][3][4][5] , gtrI, and oac), 1c (wzx [1][2][3][4][5] , gtrI, and gtrIC), 2a (wzx [1][2][3][4][5] and gtrII), 2b (wzx [1][2][3][4][5] , gtrII, and gtrX), 3a (wzx [1][2][3][4][5] , oac, and gtrX), 3b (wzx [1][2][3][4][5] and oac), 4a (wzx [1][2][3][4][5] and gtrIV), 4b (wzx [1][2][3][4][5] , gtrIV, and oac), 5a (wzx [1][2][3][4]…”

“…Thus, our multiplex PCR can identify these two newly defined serotypes. Strains of serotype Xv and serotype X presented the same amplification pattern (wzx [1][2][3][4][5] and gtrX) by multiplex PCR. Therefore, they are classified into the same serotype Xv or X. Serotype Xv has been one of the most predominant serotypes in China since 2002 (21).…”

Identification and Characterization of a Novel Shigella flexneri Serotype Yv in China

“…Roborts et al [27] found that the serotype Y vaccine candidate SFL124 contained an insertion sequence (IS1) in the gtrII gene, resulting in a nonfunctional GtrII. Chen et al [28] also observed the conversion of serotype 2a to serotype Y due to a single base mutation in gtrII which led to a Cys (437) to Tyr substitution. In our previous study [25], we have identified four serotype Y and two serotype X isolates carrying a defective gtrII gene, with one having a four-base deletion (bases 1197 to 1282) and five having a single base deletion (base 1031 or 1024).…”