Identification of Shigella serotypes by restriction of amplified O-antigengene cluster

Due to the scarcity of distinctive biochemical reactions for differentiatio n of Shigella-Escherichia coli, antigenic analysis has long been used for i dentification and typing of Shigella isolates. Nevertheless, several intra- and interspecific cross-reactions have been reported to disturb serotyping assays. Shigella serotyping is also occasionally affected by the transitio n from the smooth (S) form to the rough (R) form. Thus, there is a need for the development of novel robust and discriminating methods for Shigella id entification and typing. Characteristically, all genes specifically involve d in O-antigen synthesis are clustered in E. coli, Shigella, and Salmonella . Published oligonucleotide sequences complementary to JUMPstart and gene g nd, the conserved flanking sequences upstream and downstream of O-antigen g ene clusters, were used to amplify the O-antigen gene cluster of representa tive strains of each Shigella serotype. A unique, amplified fragment was ge nerally observed for each serotype (size ranging from 6 kbp to 17 kbp). Cle arly identifiable and reproducible patterns were obtained for each serotype after MboII digestion of the products, except for S. boydii 12 which showe d two distinct patterns, and S. flexneri serotypes 1 to 5 and X and Y which showed a single pattern. A database was built with the Taxotron package al lowing automated identification of clinical Shigella isolates to all known serotypes. (C) Editions scientifiques et medicales Elsevier SAS.