Multiresistant Acinetobacter baumannii infections: epidemiology and management.

PURPOSE OF REVIEW: We present recent data about epidemiology of Acinetobacter baumannii in the hospital setting, major resistance mechanisms, and therapeutic options for infections caused by multidrug-resistant strains.

RECENT FINDINGS: A. baumannii has emerged as a major cause of healthcare-associated infections. It commonly presents resistance to multiple antimicrobial agents, including carbapenems. These strains are now ussually resistant to the rest of antipseudomonal beta-lactams and sulbactam, a beta-lactamase inhibitor with bactericide activity against A. baumannii. Rifampicin has demonstrated its effectiveness in animal models but can never be used in monotherapy because of the rapid development of resistance. Colistin, an old antibiotic, has re-emerged as a valid alternative given its excellent in-vitro activity. Numerous studies have confirmed its efficacy in serious infections, including ventilator-associated pneumonia and nosocomial meningitis, with an acceptable safety profile. Tigecycline appears as a promising therapeutic option for multidrug resistant A. baumannii, althogh more clinical data about its efficacy especially in pulmonary infections are required. The role of combination therapy or the use or colistin in alternative routes (nebulized or intrathecally) has not been established.

SUMMARY: The optimal treatment for multidrug-resistant A. baumannii nosocomial infections has not been established. Carbapenems are the mainstay of treatment in susceptible isolates. Colistin and tigecycline retain good in-vitro activity and in many cases represent the only therapeutic options.