Current State of Antimicrobial Treatment of Lower Respiratory Tract Infections Due to Carbapenem-Resistant Acinetobacter baumannii

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a worldwide non-fermenting Gram-negative bacillus responsible for potentially severe nosocomial infections, especially in critically ill patients. CRAB tends to colonize inert surfaces and epithelia, especially the respiratory tract of mechanically ventilated patients, and may then become responsible for lower respiratory tract infections, probably the more challenging infection due to the site and the multidrug-resistant phenotype which makes it difficult to establish an effective antimicrobial regimen. Despite its diffusion, data regarding the treatment of CRAB are mainly retrospective and usually heterogeneous. Current international consensus guidelines prefer the use of ampicillin/sulbactam, but the strength of recommendation and grade of evidence tend to be weak to moderate. Moreover, no specific recommendation is given for different sites of infections. The recently introduced cefiderocol still received a recommendation against its use due to the results of the first randomized clinical trial, though retrospective and observational experiences showed favourable outcomes in this setting. We reviewed the major antibacterial drugs active against CRAB and discussed their combination in lower respiratory tract infections.