(72e) Discovery and Characterization of a Novel Actin-Binding Protein From Stenotrophomonas Maltophilia

Stenotrophomonas maltophilia is a ubiquitous, Gram-negative bacteria that is of increasing concern to healthcare professionals due to intrinsic multidrug resistance and prevalence as a cause of infection in immunocompromised patients. Major challenges in preventing S. maltophilia exist, such as its high degree of genetic diversity and ability to rapidly acquire new mechanisms of drug resistance. However, relatively little is known about specific, secreted effectors from S. maltophilia that may contribute to its virulence. Through a bioinformatics-based approach, we identified a series of proteins that resembled potential T4SS effectors and investigated their potential as virulence factors. Co-localization experiments using RFP-labeled actin indicated that one of the predicted proteins (smlt3054) disrupted the organization of the actin cytoskeleton in transfected HEK293 and A549 cell lines. In vitro actin polymerization experiments and in vivo dose dependence experiments were performed using recombinantly expressed and purified smlt3054, which confirmed the actin-binding ability of smlt3054. Expression of labeled smlt3054 in clinical strains of S. maltophilia indicate the protein is expressed at the cell surface, consistent with the prediction it is a secreted effector. We also find despite the wide genetic variability of S. maltophilia, several clinical strains isolated from actual infections contain smlt3054 as well. Thus, smlt3054 represents a potential secreted effector from S. maltophilia that we believe may play a key role in its virulence.