Pathogenicity and virulence of <i>Acinetobacter baumannii</i>: Factors contributing to the fitness in healthcare settings and the infected host

<i>Acinetobacter baumannii</i> is a common cause of healthcare-associated infections and hospital outbreaks, particularly in intensive care units. Much of the success of <i>A. baumannii</i> relies on its genomic plasticity, which allows rapid adaptation to adversity and stress. The capacity to acquire novel antibiotic resistance determinants and the tolerance to stresses encountered in the hospital environment promote <i>A. baumannii</i> spread among patients and long-term contamination of the healthcare setting. This review explores virulence factors and physiological traits contributing to <i>A. baumannii</i> infection and adaptation to the hospital environment. Several cell-associated and secreted virulence factors involved in <i>A. baumannii</i> biofilm formation, cell adhesion, invasion, and persistence in the host, as well as resistance to xeric stress imposed by the healthcare settings, are illustrated to give reasons for the success of <i>A. baumannii</i> as a hospital pathogen.