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

Abstract

Shigella flexneri is the major cause of bacterial shigellosis in developing countries. S. flexneri is divided into at least 19 serotypes, the majority of which are modifications of the same basic O-antigen by glucosylation and/or O-acetylation of its sugar residues by phage encoded serotype-converting genes. Recently, a plasmid encoded phosphoethanolamine (PEtN) modification of the O-antigen has been reported, which is responsible for the presence of the MASF IV-1 determinant and results in conversion of traditional serotypes X, 4a and Y to novel serotypes Xv, 4av and Yv, respectively. In this study, we characterized 19 serotype Yv strains isolated in China. A variant of the O-antigen phosphoethanolamine transferase gene opt (formerly called lpt-O) carried by a pSFxv_2-like plasmid was found in serotype Yv strains, which specifies the phosphorylation pattern on the O-antigen of this serotype. For the majority of the O-antigen units, the PEtN modification occurs on RhaIII, while for a minority, modifications occur on both RhaII and RhaIII. Serotype-specific gene detection and PFGE analysis suggested that these serotype Yv isolates were originated from serotypes Y, Xv and 2a by acquisition of an opt-carrying plasmid and/or inactivation of serotype-specific gene gtrII or gtrX. These data, combined with those of serotypes Xv and 4av reported earlier, demonstrate that the plasmid-encoded PEtN modification is an important serotype conversion mechanism in S. flexneri, in addition to glucosylation and O-acetylation.

Serological Identification and Prevalence of a Novel O-Antigen Epitope Linked to 3- and 4- O -Acetylated Rhamnose III of Lipopolysaccharide in Shigella flexneri

“…Phosphorylation with the PEtN of Rha III and/or Rha II at position 3 was recently identified in the newly proposed S. flexneri serotypes 4av, Xv, and Yv (4,5,15,27) and possibly in atypical strains of serotypes 4, 6, and 4X (9)(10)(11)(12) and was demonstrated to confer the hosts with the MASF IV-1 (E1037) antigenic determinant. The plasmid carrying gene opt (O-antigen phosphoethanolamine transferase) mediates the PEtN modification in these serotypes (4,5,15,17).…”

“…Based on combinations of O-antigenic determinants (O factors) on the cell surface lipopolysaccharide (LPS), S. flexneri strains are subdivided into various serotypes. Up to now, a total of 19 serotypes (1a, 1b, 1c[7a], 1d, 2a, 2b, 3a, 3b, 4a, 4av, 4b, 5a, 5b, Y, Yv, X, Xv, 6, and 7b) have been reported by different research groups using the commercially available monovalent antisera kit (Denka Seiken, Japan) and monoclonal antibody reagents (MASFs) (Reagensia AB, Sweden) (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). All serotypes except for serotype 6 share an O-antigen backbone with a tetrasaccharide repeat (O-polysaccharide) composed of one N-acetylglucosamine (GlcNAc) and three rhamnose residues (Rha I , Rha II , and Rha III ) (1).…”

Evaluation of Molecular Methods for Serotyping Shigella flexneri

“…Currently, there are 15 well-established S. flexneri serotypes (1a, 1b, 1c, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, X, Xv, Y, and F6), which are composed of type (I, II, III, IV, and V)-, group (3:4, 6, and 7:8)-and 1c-specific antigenic determinants (6). The O-antigen modification that results in the addition of phosphoethanolamine (PEtN) to either Rha II or Rha III, mediated by opt, is found in serotypes 4a variant (4av), X variant (Xv), and Y variant (Yv) (7,8).…”

Genomic Portrait of the Evolution and Epidemic Spread of a Recently Emerged Multidrug-Resistant Shigella flexneri Clone in China

“…S. flexneri is divided into at least 19 serotypes (serotypes 1a, 1b, 1c, 1d, 2a, 2b, 3a, 3b, 4a, 4av, 4b, 5a, 5b, X, Xv, Y, Yv, F6, and 7b), based on the combinations of antigenic determinants present on the O antigen of the cell envelope lipopolysaccharide (LPS) (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Serotypes 1c, 4av, 7b, 1d, Yv, and Xv were new serotypes reported in recent years (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), among which serotypes 1c and Xv have caused epidemic-level disease (5,7,9). Serotype Xv first appeared in 2000 in Henan province and subsequently replaced serotype 2a to become the predominant serotype in Henan between 2002 and 2006.…”