Influence of severity of infection on the effect of appropriate antimicrobial therapy forAcinetobacter baumanniibacteremic pneumonia

Background The impact of appropriate antimicrobial therapy forA. baumanniibacteremic pneumonia has not been well established due to the inclusion of the three phenotypically indistinguishableAcinetobacterspecies and confounding factors including underlying diseases and severity of infection. This retrospective study aimed to evaluate the impact of appropriate antimicrobial therapy on 14-day mortality inA. baumanniibacteremic pneumonia patients after adjusting for risk factors. Methods This study was conducted at five medical centers in Taiwan between July 2012 and June 2016.A. baumanniispecies identification was performed using reference molecular methods. Risk factors for 14-day mortality were analyzed via logistic regression. The interaction between the Acute Physiology and Chronic Health Evaluation (APACHE) II score and appropriate antimicrobial therapy was assessed using the logistic model. Results A total of 336 patients with monomicrobialA. baumanniibacteremic pneumonia were included in this study. The overall 14-day mortality rate was 47.3%. The crude mortality of appropriate antimicrobial therapy was 35.9% (57 of 151 patients). Appropriate antimicrobial therapy was associated with a lower mortality after multivariate adjustment (odds ratio [OR], 0.57; 95% confidence interval [CI], 0.34-0.97;p = 0.04), and the effect was influenced by APACHE II score (OR for interaction term, 0.0098; 95% CI, 0.0005-0.1885;p = 0.002). Further analysis demonstrated that appropriate antimicrobial therapy significantly reduced 14-day mortality among the patients with an APACHE II score > 35 (OR 0.0098; 95% CI 0.0005-0.1885). Conclusion Appropriate antimicrobial therapy decreases 14-day mortality of the most severely ill patients withA. baumanniibacteremic pneumonia.