Virulence of Environmental Stenotrophomonas maltophilia Serologically Cross-reacting with Shigella-specific Antisera

This research involved an environmental strain of Stenotrophomonas maltophilia which has been reported to produce serological cross-reactivity with Shigella dysenteriae type 8 specific antisera. Since clinical diagnosis of shigellosis is largely based on culture and serology, the investigation was aimed at in vivo and in vitro virulence comparison between the culturally similar environmental S. maltophilia isolate and the reference S. dysenteriae strains. The findings of this study revealed the absence of virulent genes of Shigella sp. like ipaH, virA and stx1 and characteristic invasive large plasmid in the test isolate. The Western blot analysis revealed that serological cross-reactivity of Stenotrophomonas maltophilia was due to certain protein component(s) in its outer membrane. The isolate was capable of producing extracellular protease, exhibited alpha hemolysis and was negative for hemagglutinating assay. The isolate gave negative reaction with rabbit ileal loop and Sereny tests. The S. maltophilia isolate did not possess any enterotoxic or invasive property as that of virulent S. dysenteriae strains. Further characterizations and adequate genetic manipulations of this environmental isolate may contribute to the development of a potential vaccine candidate for shigellosis.