e Carbapenems are considered the treatment of choice for Acinetobacter baumannii infections. Many facilities implement preventive measures toward only carbapenem-resistant A. baumannii (CRAB). However, the independent role of the carbapenem resistance determinant on patient outcomes remains controversial. In a 6-year analysis of adults with A. baumannii bloodstream infection (BSI), the outcomes of 149 CRAB isolates were compared to those of 91 patients with carbapenem-susceptible A. baumannii. In bivariable analyses, CRAB BSIs were significantly associated with worse outcomes and with a delay in the initiation of appropriate antimicrobial therapy (DAAT). However, in multivariable analyses, carbapenem resistance status was no longer associated with poor outcomes, while DAAT remained an independent predictor. The epidemiological significance of A. baumannii should not be determined by its resistance to carbapenems.
Acinetobacter baumannii is one of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, A. baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens (1), which result in a variety of serious infectious clinical syndromes (2-4). Apart from a continuous increment in incidence, offending human strains have also become more resistant (5). The prevalence of the extensively drug-resistant (XDR) A. baumannii phenotype (6) has increased exponentially worldwide (5,7,8).Carbapenems are considered the agents of choice for treating A. baumannii infections, as long as the isolates are susceptible (4, 9, 10). Therefore, resistance to carbapenems frequently determines the epidemiological significance of the pathogen (2, 10). Many hospitals utilize infection control preventive measures (isolation precautions, cohorting, and screening for asymptomatic carriage), targeting only patients with carbapenem-resistant A. baumannii (CRAB) strains (11). However, both molecular epidemiology and clinical epidemiology investigations do not support these practices. Many of the mechanisms of resistance to carbapenems are chromosomally encoded (12). Therefore, it might be appropriate to target the prevention of patient-to-patient transmission of all A. baumannii isolates, since even susceptible organisms might become resistant after they are acquired by a new host. Moreover, controlled clinical data correlating resistance to carbapenems with worse patient outcomes were subjected to several biases, i.e., the majority of studies had low sample size, infection was not appropriately differentiated from colonization, and most studies did not control for time to initiation of appropriate antimicrobial therapy (13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Delay in initiating appropriate antimicrobial therapy (DAAT) is the strongest modifiable predictor of worse outcomes among septic patients (23,24), and DAAT has frequently been reported in A. baumannii infections (25). Therefore, the aim of this study was to explore the independent role of the carbapenem resistance phenotype on the clinical outcomes of pat...