Outer membrane Protein A plays a role in pathogenesis of Acinetobacter nosocomialis

Acinetobacter nosocomialis is an important nosocomial pathogen that causes a variety of human infections. However, the specific virulence factors of this microorganism have not yet been determined. We investigated the role of outer membrane protein A (OmpA) in the pathogenesis of A. nosocomialis. A ΔompA mutant of the A. nosocomialis ATCC 17903(T) strain was constructed using markerless gene deletion. The ΔompA mutant displayed reduced biofilm formation in polystyrene tubes and reduced adherence to A549 cells in comparison to the wild-type strain. These virulence traits of the ΔompA mutant strain were restored when the ompA gene was complemented. Cytotoxicity was not significantly different between the wild-type strain and the ΔompA mutant when A549 cells were infected with bacteria or treated with outer membrane vesicles (OMVs). However, OMVs from the wild-type strain induced cytotoxicity in HEp-2 cells, whereas OMVs from the ΔompA mutant did not induce cytotoxicity. Proteomic analysis of OMVs revealed that OmpA influenced the distribution of envelope and periplasmic proteins. Overall, this study is the first report that links OmpA to A. nosocomialis pathogenesis, and highlights OmpA as a putative target to develop anti-virulence agents or vaccines against A. nosocomialis infection.