O-Antigen Gene Clusters of Plesiomonas shigelloides Serogroups and Its Application in Development of a Molecular Serotyping Scheme.

Plesiomonas shigelloides is a Gram-negative, flagellated, rod-shaped, ubiquitous, and facultative anaerobic bacterium. It has been isolated from various sources, such as freshwater, surface water, and many wild and domestic animals. P. shigelloides is associated with diarrheal diseases of acute secretory gastroenteritis, an invasive shigellosis-like disease, and a cholera-like illness in humans. At present, 102 somatic antigens and 51 flagellar antigens of P. shigelloides have been recognized; however, very little is known about variations of O-antigens among P. shigelloides species. In this study, 12 O-antigen gene clusters of P. shigelloides, O2H1a1c (G5877), O10H41 (G5892), O12H35 (G5890), O23H1a1c (G5263), O25H3 (G5879), O26H1a1c (G5889), O32H37 (G5880), O33H38 (G5881), O34H34 (G5882), O66H3 (G5270), O75H34 (G5885), and O76H39 (G5886), were sequenced and analyzed. The genes that control O-antigen synthesis are present as chromosomal gene clusters that maps between rep and aqpZ, and most of the synthesis and translocation of OPS (O-specific polysaccharide) belongs to Wzx/Wzy pathway with the exception of O12, O25, and O66, which use the ATP-binding cassette (ABC) transporter pathway. Phylogenetic analysis of wzx and wzy show that the wzx and wzy genes are specific to individual O-antigens and can be used as targets in molecular typing. Based on the sequence data, an O-antigen specific suspension array that detects 12 distinct OPS' has been developed. This is the first report to catalog the genetic features of P. shigelloides O-antigen variations and develop a suspension array for the molecular typing. The method has several advantages over traditional bacteriophage and serum agglutination methods and lays the foundation for easier identification and detection of additional O-antigen in the future.