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

Abstract

This retrospective observational study assessed the differences between monomicrobial and polymicrobial <i>A. baumannii</i> bacteremia and identified possible independent risk factors for 14-day mortality. There were 379 patients with <i>A. baumannii</i> 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 <i>A. baumannii</i> bacteremia (26.9% vs. 29.2%, <i>p</i> = 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 <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>, and <i>Enterobacter</i> spp. from the bloodstream. Compared with patients with monomicrobial multidrug-resistant <i>A. baumannii</i> (MDRAb) bacteremia, those with MDRAb concomitant with Gram-negative bacilli bacteremia had a worse outcome. Polymicrobial <i>A. baumannii</i> bacteremia was not associated with a higher 14-day mortality rate than that of monomicrobial <i>A. baumannii</i> bacteremia, although more deaths were observed when certain Gram-negative bacteria were concomitantly isolated. Appropriate antimicrobial therapy remains an important life-saving measure for <i>A. baumannii</i> bacteremic patients.