Comparison of Virulence Attributable to Different Levels of Antimicrobial Resistant Acinetobacter baumannii Bacteremia

Abstract

Objective: To determine the mortality rate and severity of sepsis in patients who have acquired drug resistant Acinetobacter baumannii (AB) bacteremia (ABB). Materials and Methods: Microbiology data and information of adult patients hospitalized at Songklanagarind Hospital with positive blood culture for AB between January 2008 and April 2017 were retrieved and reviewed. Antimicrobial resistance was classified into four categories comprising of non-multidrug-resistant (nMDR), multidrug-resistant (MDR), extensively-drug-resistant (XDR), and possible-pandrug-resistant (pPDR). The primary outcome of bacteremia was the in-hospital mortality rate, with the additional outcome, being severity of sepsis represented by the Sepsis Severity Score (SSS). The differences in mortality rates were assessed by Cox proportional hazard model. Results of analysis were reported in terms of hazard ratio (HR) and corresponding 95% confidence interval (CI). Comparison of SSS was evaluated by generalized linear model (GLM) and reported in term of odds ratio (OR). Results: The present study identified 480 patients with hospital-acquired ABB. The proportions among resistance categories were 11%, 39%, 47%, and 3% with crude mortality rates of 20%, 34%, 69%, and 75% for nMDR, MDR, XDR, and pPDR, respectively. GLM analysis showed ORs for higher SSS score in the appropriate treated MDR, and XDR were 1.09 (1.01 to 1.19), and 1.12 (1.03 to 1.22), respectively. The inappropriate treatment ORs for nMDR, MDR, XDR, and pPDR were 1.17 (0.99 to 1.39), 1.30 (1.17 to 1.45), 1.17 (1.08 to 1.28), and 1.01 (0.87 to 1.17), respectively. Conclusion: The virulence of AB was not reduced when its level of antibiotic resistance was upgraded. Keywords: Acinetobacter baumannii; Drug resistance; Bacteremia; Mortality; Virulence