Genetic analysis and serological detection of Novel O-antigen gene clusters of Plesiomonas shigelloides.

Plesiomonas shigelloides, a member of the family Vibrionaceae, is a Gram-negative facultative anaerobic bacterium with flagella and rod-shaped. P. shigelloides has been isolated from such sources as freshwater, surface water, and many wild and domestic animals. P. shigelloides contains 102 O-antigens and 51 H-antigens. The diversity of O-antigen gene clusters is relatively poorly understood. In addition to O1 and O17 reported by other laboratories, and the 12 O serogroups (O2, O10, O12, O23, O25, O26, O32, O33, O34, O66, O75, and O76) reported previously by us, in the present study, nine new P. shigelloides serogroups (O8, O17, O18, O37, O38, O39, O44, O45, and O61) were sequenced and annotated. The genes for the O-antigens of these nine groups are clustered together in the chromosome between rep and aqpZ. Only O38 possesses the wzm and wzt genes for the synthesis and translocation of O-antigens via the ATP-binding cassette (ABC) transporter pathway; the other eight use the Wzx/Wzy pathway. Phylogenetic analysis using wzx and wzy showed that both of them are diversified. Among the nine P. shigelloides serogroups, eight of them use wzx/wzy genes as targets. An O-antigen specific PCR assay that detects nine of the distinct serogroups was developed with no cross reactions among them.