Code blue: A cinetobacter baumannii , a nosocomial pathogen with a role in the oral cavity

Summary Actinetobacter baumannii is an important nosocomial pathogen that can cause a wide range of serious conditions including pneumonia, meningitis, necrotizing fasciitis and sepsis. It is also a major cause of wound infections in military personnel injured during the conflicts in A fghanistan and I raq, leading to its popular nickname of ‘ I raqibacter’. Contributing to its success in clinical settings is resistance to environmental stresses such as desiccation and disinfectants. Moreover, in recent years there has been a dramatic increase in the number of A . baumannii strains with resistance to multiple antibiotic classes. Acinetobacter baumannii is an inhabitant of oral biofilms, which can act as a reservoir for pneumonia and chronic obstructive pulmonary disease. Subgingival colonization by A . baumannii increases the risk of refractory periodontitis. Pathogenesis of the organism involves adherence, biofilm formation and iron acquisition. In addition, A . baumannii can induce apoptotic cell death in epithelial cells and kill hyphal forms of C andida albicans . Virulence factors that have been identified include pili, the outer membrane protein O mp A , phospholipases and extracellular polysaccharide. Acinetobacter baumannii can sense blue light through a blue‐light sensing using flavin ( BLUF ) domain protein, B ls A . The resulting conformational change in B ls A leads to changes in gene expression, including virulence genes.