Design of Two Multiplex PCR Assays for Serotyping Shigella flexneri.

Shigella flexneri is a major health problem in developing countries. There are 19 serotypes recognized based on O-antigen structure and its typing is important for epidemiological purposes. However, the diversity of serotypes and the difficulties presented by phenotypic serotyping, for example, unavailable antisera for less common antigens, require the implementation of molecular techniques. In this study, we developed two multiplex PCR assays targeting the O-antigen synthesis genes and the O-antigen modification genes, for the rapid identification of S. flexneri serotypes 1/7, 2, 4, 5, and 6 (PCR A) and serotype 7 and group antigenic factors (3,4; 6; 7,8; E1037) (PCR B). A total of 73 S. flexneri strains representing 18 serotypes, except serotype 1d, were used in the study. Specific amplification patterns were obtained for each of the different serotypes. All strains tested had concordant results with phenotypic and genotypic serotyping; therefore, its implementation in the microbiology clinical laboratory will significantly improve S. flexneri serotyping.

AA479 antiserum: new reagent for the serotype characterization of atypical variants of Shigella flexneri.

Shigella flexneri is divided into 13 serotypes based on the combination of antigenic determinants present in the O-antigen. A new O-antigen modification with phosphoethanolamine has been identified. The presence of this antigenic determinant (called E1037) is recognized by monoclonal antibody MASF IV-1. Given the increasing incidence of these new variants and the difficulty in supplying the monoclonal antibody to our country, we produced a polyclonal antiserum (AA479) through immunization with a S. flexneri Xv strain. The antiserum specificity was assessed by slide agglutination against isolates from clinical cases and a culture collection representing all Shigella serotypes. The results obtained demonstrated a 100% correlation between AA479 absorbed antiserum and monoclonal antibody MASF IV-1. The availability of AA479 antiserum in every public hospital in Argentina will allow us to identify atypical S. flexneri isolates in order to strengthen Shigella surveillance in our country and to compare with global epidemiological data.

AA479 antiserum: new reagent for the serotype characterization of atypical variants of Shigella flexneri. / AA479 antiserum: new reagent for the serotype characterization of atypical variants of Shigella flexneri.

Shigella flexneri is divided into 13 serotypes based on the combination of antigenic determinants present in the O-antigen. A new O-antigen modification with phosphoethanolamine has been identified. The presence of this antigenic determinant (called E1037) is recognized by monoclonal antibody MASF IV-1. Given the increasing incidence of these new variants and the difficulty in supplying the monoclonal antibody to our country, we produced a polyclonal antiserum (AA479) through immunization with a S. flexneri Xv strain. The antiserum specificity was assessed by slide agglutination against isolates from clinical cases and a culture collection representing all Shigella serotypes. The results obtained demonstrated a 100

correlation between AA479 absorbed antiserum and monoclonal antibody MASF IV-1. The availability of AA479 antiserum in every public hospital in Argentina will allow us to identify atypical S. flexneri isolates in order to strengthen Shigella surveillance in our country and to compare with global epidemiological data.