The rpf/DSF signalling system of Stenotrophomonas maltophilia positively regulates biofilm formation, production of virulence-associated factors and [beta]-lactamase induction

Stenotrophomonas maltophilia is a multidrug-resistant opportunistic pathogen. S. maltophilia quorum-sensing system is mediated by the diffusible signal factor (DSF), which synthesis depends on rpfF. It has been reported that rpfF disruption in S. maltophilia K279a leads to a loss of DSF synthesis, reduced levels of extracellular protease, swarming motility and virulence in the Galleria mellonella model. The aim of this work was to attain a deeper knowledge of the role of the rpf/DSF signalling system in S. maltophilia biofilm formation, phenotypic traits associated with biofilm development and virulence and antimicrobial susceptibility. To this end, comparative studies were conducted on S. maltophilia K279a and K279arpfF. The results presented here put in evidence the positive role of DSF in bacterial growth, biofilm formation, swimming and twitching motilities, DNAse, lipases and siderophores production as well as resistance to oxidative stress. Interestingly, DSF seems to be essential for the development of the spatially organised structure seen in mature biofilms. Therefore, DSF from S. maltophlia K279a positively regulates biofilm formation and virulence. Furthermore, DSF is necessary for the induction of L1 and L2 [beta]-lactamase production in K279a. This is the first evidence of the role of the rpf/DSF signalling system in S. maltophilia [beta]-lactam resistance.