Role of the AmvAR efflux system on the pathogenesis of Acinetobacter baumannii

Active extrusion is a key mechanism by which efflux pumps enable nosocomial pathogens to withstand exposure to antimicrobial compounds. In Acinetobacter baumannii, the AmvA efflux pump, belonging to the Major Facilitator Superfamily (MFS) and regulated by the TetR-family repressor AmvR, reduces susceptibility to disinfectants. Here, we investigated the broader functions of the AmvAR system beyond antimicrobial efflux. Our findings demonstrate that, in addition to conferring reduced susceptibility to disinfectants, the AmvAR system regulates the expression of cell surface components linked to pathogenic traits. Specifically, the A. baumannii AmvAR system contributes to motility and cell adhesion, thereby influencing biofilm formation. Loss of either the AmvA efflux pump or its transcriptional regulator AmvR significantly reduced biofilm development. Furthermore, disruption of regulatory control within this system led to a significant upregulation of the csuA pilus gene. Collectively, these results highlight the role of the AmvAR system in the pathogenesis of A. baumannii, underscoring its potential as a therapeutic target.