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.