The intracellular life of Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative opportunistic bacterium responsible for nosocomial and community-acquired infections. This pathogen is globally disseminated and associated with high levels of antibiotic resistance, which makes it an important threat to human health. Recently, new evidence showed that several A. baumannii isolates can survive and proliferate within eukaryotic professional and/or nonprofessional phagocytic cells, with in vivo consequences. This review provides updated information and describes the tools that A. baumannii possesses to adhere, colonize, and replicate in host cells. Additionally, we emphasize the high genetic and phenotypic heterogeneity detected amongst A. baumannii isolates and its impact on the bacterial intracellular features. We also discuss the need for standardized methods to characterize this pathogen robustly and consequently consider some strains as facultative intracellular bacteria.