Table 1.

Summarized information regarding the general microbial virulence factors arsenal detected in A. baumannii.

Virulence Factors	Functions
Capsule (CPS)	Antimicrobial resistance, host–pathogen interactions and pathogenesis
Efflux pumps	Antimicrobial resistance, biofilm formation, disinfectant resistance, heavy metal resistance and response to oxidative and osmotic stresses
Lipopolysaccharide (LPS)	Antimicrobial resistance, bacterial motility and induction of pro-inflammatory cytokines in humans
Lipooligosaccharide (LOS)	Antimicrobial resistance, bacterial adhesion, resistance to human opsono-phagocytosis and induction of pro-inflammatory cytokines in humans
Outer membrane proteins (OMPs)	Antimicrobial resistance, induction of apoptosis in human cells, bacterial adhesion, invasion and dissemination, cytotoxicity in human cells, host–pathogen interactions, induction of reactive oxygen species (ROS) in human cells, metal ion acquisition and substrate translocation
Pili	Bacterial adhesion, bacterial attachment (irreversible), biofilm formation, genetic exchange through HGT and motility (e.g., twitching)
Metal ion uptake systems	Bacterial metal (e.g., Zn, Fe, Mn) uptake, translocation, metabolism homeostasis, biofilm formation, quorum sensing regulation and response to oxidative stress
Two-component systems (TCSs)	Antimicrobial resistance, aromatic compound metabolism, bacterial pathogenesis, biofilm formation, capsule expression, regulation of bacterial motility, lipid A modification, regulation of some groups of efflux pumps and resistance to human serum
Secretion systems (SSs)	Antimicrobial resistance, bacterial adhesion, biofilm formation, bacterial colonization and proliferation within the human cells, bacterial survival, enzyme and toxin secretion, induction of apoptosis in human cells, genetic elements exchange via HGT and pathogenesis