Genomic attributes differ between Vibrio parahaemolyticus environmental and clinical isolates including pathotypes.

Vibrio parahaemolyticus is a marine bacterium and causes opportunistic gastroenteritis in humans. Clinical strains of V. parahaemolyticus contain haemolysin and type III secretion systems (T3SS) that define their pathotype. A growing number of strains isolated recently from the environment have acquired these virulence genes constituting a pool of potential pathogens. This study used comparative genomics to identify genetic factors that delineate environmental and clinical V. parahaemolyticus population and understand the similarities and differences between the T3SS2 phylotypes. The comparative analysis revealed the presence of a cluster of genes belonging to bacterial cellulose synthesis (bcs) in isolates of environmental origin. This cluster, previously unreported in V. parahaemolyticus, exhibit significant similarity to that of Aliivibrio fischeri, and might dictate a potentially new mechanism of its environmental adaptation and persistence. The study also identified many genes predicted in silico to be T3SS effectors that are unique to T3SS2ß of tdh- trh+ and tdh+ trh+ pathotype and having no identifiable homologue in tdh+ trh- T3SS2α. Overall, these findings highlight the importance of understanding the genes and strategies V. parahaemolyticus utilize for the myriad interactions with its hosts, either marine invertebrates or humans.

Tryptanthrin, a potential biofilm inhibitor against toxigenic Vibrio cholerae, modulating the global quorum sensing regulator, LuxO.

Cholera caused by the Gram-negative bacterium Vibrio cholerae still remains a major health burden in developing countries due to its high transmissibility and multidrug resistance. Alternative strategies are in quest to curtail the disease focusing on antivirulent approaches, such as biofilm inhibition, which make bacteria more susceptible to antibiotic therapies. The biofilm state is important for V. cholerae pathogenesis and its persistence in the environment. In the present study, tryptanthrin, a phytochemical, has been identified as possessing strong anti-biofilm activity at sub MIC (2 µg ml-1) against V. cholerae. LuxO was identified as the putative target of tryptanthrin by molecular docking and real time analysis. The phytochemical was identified as safe and possessed synergistic action with ciprofloxacin, a commonly used quinolone antibiotic to treat cholera. Collectively, the study establishes the first report on the anti-biofilm property of tryptanthrin by targeting LuxO, which could serve as a potential antivirulent therapy to combat V. cholerae infections.