Acinetobacter infections - Epidemiology and pathogenesis of a significant healthcare-associated pathogen

The genus Acinetobacter contains a heterogeneous array of environmental and commensal organisms. The majority of these strains are non-pathogenic; however, A. baumannii has emerged as a common nosocomial pathogen. Groups with the highest risk of A. baumannii infection include immunocompromised and critically ill patients, and those undergoing long-term care following severe burns or traumatic injury. In these patients A. baumannii can cause wound infections, pneumonia, and sepsis resulting in prolonged recovery time, longer hospital stays, and in some cases can be a contributing factor in mortality. The rise to prominence of A. baumannii in the healthcare setting can be attributed to intrinsic resistance to desiccation and chemical disinfectants, which allow the organism to persist on surfaces. This persistence provides a constant reservoir for transmission and can result in recurrent outbreaks within hospital units. Additionally, numerous native antibiotic resistance mechanisms along with the evolution of novel resistance through mutation or horizontal gene transfer has resulted in multi-drug resistant (MDR) strains which demonstrate resistance to nearly every available class of antibiotic. While the development of new antibiotics such as tigecycline holds some promise for treating these resistant strains, the best interventional strategy is to prevent nosocomial spread through the use of screening, contact isolation and good hand hygiene practices.