Influence of severity of infection on the effect of appropriate antimicrobial therapy for Acinetobacter baumannii bacteremic pneumonia.

BACKGROUND: The impact of appropriate antimicrobial therapy for A. baumannii bacteremic pneumonia has not been well established due to the inclusion of the three phenotypically indistinguishable Acinetobacter species 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 in A. baumannii bacteremic 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. baumannii species 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 monomicrobial A. baumannii bacteremic 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 with A. baumannii bacteremic pneumonia.

Is Polymicrobial Bacteremia an Independent Risk Factor for Mortality in Acinetobacter baumannii Bacteremia?

This retrospective observational study assessed the differences between monomicrobial and polymicrobial A. baumannii bacteremia and identified possible independent risk factors for 14-day mortality. There were 379 patients with A. baumannii bacteremia admitted to a tertiary care center in northern Taiwan between August 2008 and July 2015 enrolled for data analysis. Among them, 89 patients (23.5%) had polymicrobial bacteremia and 290 patients (76.5%) had monomicrobial bacteremia. No significant difference in 14-day mortality was observed between patients with monomicrobial and polymicrobial A. baumannii bacteremia (26.9% vs. 29.2%, p = 0.77). Logistic regression controlled for confounders demonstrated that polymicrobial bacteremia was not an independent predictor of mortality, whereas appropriate antimicrobial therapy was independently associated with reduced mortality. Higher 14-day mortality rates were observed in the polymicrobial bacteremic patients with concomitant isolation of Escherichia coli, Pseudomonas aeruginosa, and Enterobacter spp. from the bloodstream. Compared with patients with monomicrobial multidrug-resistant A. baumannii (MDRAb) bacteremia, those with MDRAb concomitant with Gram-negative bacilli bacteremia had a worse outcome. Polymicrobial A. baumannii bacteremia was not associated with a higher 14-day mortality rate than that of monomicrobial A. baumannii bacteremia, although more deaths were observed when certain Gram-negative bacteria were concomitantly isolated. Appropriate antimicrobial therapy remains an important life-saving measure for A. baumannii bacteremic patients.