Exposure to quinolones is associated with carbapenem resistance among colistin-susceptible Acinetobacter baumannii blood isolates

Abstract

In this study, we explored risk factors associated with bacteraemia caused by colistin-susceptible/carbapenem-resistant (Co S/Ca R) Acinetobacter baumannii. A retrospective cohort study of hospitalised patients with A. baumannii bacteraemia was performed at a tertiary care hospital over a 44-month period. Thirty-nine patients with bacteraemia due to A. baumannii (35 Intensive Care Unit and 4 ward patients) were included in the analysis. Twenty-five patients (64%) had bacteraemia due to Co S/Ca R A. baumannii and 14 patients (36%) had bacteraemia due to colistin-susceptible/carbapenem-susceptible A. baumannii. Mortality was 56% (14/25) and 35.7% (5/14) for patients in the two groups, respectively ( P = 0.22). Bivariate analysis showed that prior exposure to fluoroquinolones ( P = 0.01) and antipseudomonal penicillins ( P = 0.004) as well as a higher number of antibiotics in use on the day of bacteraemia ( P = 0.02) were associated with isolation of a Co S/Ca R strain among patients with A. baumannii bacteraemia. Multivariate analysis using a backward logistic regression model showed that only exposure to fluoroquinolones was associated with development of Co S/Ca R A. baumannii bacteraemia (odds ratio = 11.6; 95% confidence interval 2.4–55.9; P = 0.02). The appearance of Co S/Ca R A. baumannii infections represents a major threat to critically ill hospitalised patients. Exposure to fluoroquinolones is an independent risk factor for development of Co S/Ca R A. baumannii bacteraemia.