Extensively drug-resistant Acinetobacter baumannii: risk factors for acquisition and prevalent OXA-type carbapenemases--a multicentre study.

In this study, we investigated the risk factors for and carbapenem resistance mechanisms of extensively drug-resistant Acinetobacter baumannii (XDR-AB). Isolates of XDR-AB were collected from seven tertiary care hospitals in South Korea. A case-control study for risk factor analysis was performed and the presence of the metallo-β-lactamase (MBL) and OXA genes was examined. The control group consisted of adult inpatients receiving care from the same hospital. XDR-AB were isolated from 26 patients who were studied for risk factor analysis. Third-generation cephalosporin use [odds ratio (OR)=9.6, 95% confidence interval (CI) 1.3-171.3; P=0.02] and Acute Physiology and Chronic Health Evaluation (APACHE) II score (OR=1.2, 95% CI 1.1-1.5; P=0.004) were identified as risk factors for acquisition of XDR-AB. Pulsed-field gel electrophoresis (PFGE) showed clonal epidemic isolates in hospitals. MBLs were not detected, and all 30 XDR-AB isolates had upregulated OXA-type carbapenemase genes. These results suggest that third-generation cephalosporin use and disease severity are associated with XDR-AB acquisition amongst typical adult inpatients. This study also points to intrahospital spread of XDR-AB. Upregulated OXA-type carbapenemases are prevalent in XDR-AB founded in South Korean hospitals.