Trigger Factor in Burkholderia pseudomallei is essential for key virulence determinants, including host cell internalization, cytotoxicity, motility, and stress resistance

UNLABELLED: Burkholderia pseudomallei is a facultative intracellular pathogen and the causative agent of melioidosis. Treatment of this deadly infection is both protracted and limited to only a select number of antibiotics. Not only can patients suffer adverse reactions to prolonged therapy, but resistance has also been reported in several clinical isolates. Therefore, it is essential to identify new drug targets to combat this infection. One approach is to identify and target proteins that are involved in bacterial virulence. Trigger Factor (TF) belongs to the FK506-binding protein family and functions as both a peptidyl-prolyl cis-trans isomerase and as a chaperone. TF has been shown to be important for virulence in gram-positive bacteria. However, very limited information is available about the contribution of TF to virulence in B. pseudomallei or other pathogenic gram-negative bacteria. In this study, the B. pseudomallei TF homolog (BPSL1402) was enzymatically characterized, and a deletion mutant was generated to investigate the role of TF in virulence. Comparative proteomic analysis coupled with cell-based infection and phenotypic assays revealed that deletion of tig in B. pseudomallei resulted in pleiotropic effects on multiple virulence mechanisms. The Bp∆tig mutant was highly attenuated in cells, showing defects in adhesion and internalization, as well as reduced cell cytotoxicity. Furthermore, the mutant demonstrated altered capsule and lipopolysaccharide production, increased biofilm formation, reduced motility, and increased susceptibility to oxidative and pH stresses. The results in this study indicate that tig is important for the virulence of B. pseudomallei and is a potential target for anti-virulence therapy. IMPORTANCE: Melioidosis is a potentially fatal infection caused by Burkholderia pseudomallei, a bacterium that is intrinsically resistant to many commonly used antibiotics. Therefore, the identification of new drug targets is essential for the development of new and effective therapies. This study demonstrates that the Trigger Factor protein, encoded by BPSL1402, is important for the establishment of B. pseudomallei infection and is involved in multiple facets of virulence, including motility, cell cytotoxicity, and resistance to stress. With reports of B. pseudomallei isolated from new regions and resistance to current treatment options, the significance of this research is the identification of a novel B. pseudomallei virulence factor that can be potentially exploited for the development of new therapeutics to treat this deadly infection.