The Outer Membrane Proteins OmpA, CarO, and OprD ofAcinetobacter baumanniiConfer a Two-Pronged Defense in Facilitating Its Success as a Potent Human Pathogen

Of all theESKAPEpathogens, carbapenem-resistant and multidrug-resistantAcinetobacter baumanniiis the leading cause of hospital-acquired and ventilator-associated pneumonia.A. baumanniiinfections are notoriously hard to eradicate due to its propensity to rapidly acquire multitude of resistance determinants and the virulence factor cornucopia elucidated by the bacterium that help it fend off a wide range of adverse conditions imposed upon by host and environment. One such weapon in the arsenal ofA. baumanniiis the outer membrane protein (OMP) compendium. OMPs inA. baumanniiplay distinctive roles in facilitating the bacterial acclimatization to antibiotic- and host-induced stresses, albeit following entirely different mechanisms. OMPs are major immunogenic proteins in bacteria conferring bacteria host-fitness advantages including immune evasion, stress tolerance, and resistance to antibiotics and antibacterials. In this review, we summarize the current knowledge of majorA. baumanniiOMPs and discuss their versatile role in antibiotic resistance and virulence. Specifically, we explore how OmpA, CarO, and OprD-like porins mediate antibiotic and amino acid shuttle and host virulence.