Flagellar-mediated motility is a crucial virulence factor in many bacterial species. A dual flagellar system has been described in aeromonads; however, there is no flagella-related study in the emergent human pathogen Aeromonas dhakensis. Using 46 clinical A. dhakensis, phenotypic motility, genotypic characteristics (flagellar genes and sequence types), biochemical properties and their relationship were investigated in this study. All 46 strains showed swimming motility at 30 °C in 0.3% Bacto agar and carried the most prevalent 6 polar flagellar genes cheA, flgE, flgG, flgH, flgL, and flgN. On the contrary, only 18 strains (39%) demonstrated swarming motility on 0.5% Eiken agar at 30 °C and they harbored 11 lateral flagellar genes lafB, lafK, lafS, lafT, lafU, flgCL, flgGL, flgNL, fliEL, fliFL, and fliGL. No association was found between biochemical properties and motility phenotypes. Interestingly, a significant association between swarming and strains isolated from pus was observed (p = 0.0171). Three strains 187, 277, and 289 isolated from pus belonged to novel sequence types (ST522 and ST524) exhibited fast swimming and swarming profiles, and they harbored > 90% of the flagellar genes tested. Our findings provide a fundamental understanding of flagellar-mediated motility in A. dhakensis.
Aeromonas dhakensis possesses dual flagellar systems for motility under different environments. Flagella-mediated motility is necessary for biofilm formation through an initial attachment of bacteria to the surface, but this has not been elucidated in A. dhakensis. This study investigates the role of polar (flaH, maf1) and lateral (lafB, lafK and lafS) flagellar genes in the biofilm formation of a clinical A. dhakensis strain WT187 isolated from burn wound infection. Five deletion mutants and corresponding complemented strains were constructed using pDM4 and pBAD33 vectors, respectively, and analyzed for motility and biofilm formation using crystal violet staining and real-time impedance-based assays. All mutants were significantly reduced in swimming (p