Risk Factors Associated with Colistin-Resistant Acinetobacter baumannii Infection

Acinetobacter baumannii is an important cause of healthcare-associated infections and is resistant to almost all antimicrobial agents, with strains recently reported to be resistant to colistin. In this study, we aimed to identify the risk factors associated with colistin-resistant A. baumannii infections by comparing colistin-resistant and -susceptible A. baumannii isolates. We retrospectively reviewed the medical records of 51 and 100 cases in which colistin-resistant and -susceptible A. baumannii were isolated, respectively. Univariate analysis showed that compared with patients with colistin-sensitive infections, patients with colistin-resistant A. baumannii infections had a combined pulmonary disease (P = 0.017), were admitted to intensive care unit (P = 0.020), and had prior mechanical ventilation (P = 0.003), tracheostomy (P = 0.043), percutaneous drainage (P = 0.070), hemodialysis (P = 0.002); use of colistin (P = 0.000), carbapenem (P = 0.000), and teicoplanin (P =0.004); and co-infection (P = 0.035). Multivariate analysis indicated that eight variables were related to the likelihood of colistin-resistant A. baumannii infections: use of teicoplanin (odds ratio [OR]: 3.140, 95% confidence interval [CI]: 0.529–18.650), prior hemodialysis (OR: 2.722, 95% CI: 0.851–8.709),combined pulmonary disease (OR: 2.286, 95% CI: 0.998–5.283), prior use of carbapenem (OR: 0.199, 95% CI: 0.863–5.603), co-infection (OR: 1.706, 95% CI: 0.746–3.898), prior mechanical ventilation (OR: 1.614, 95% CI, 0.684–3.809), intensive care unit admission (OR: 1.387, 95% CI: 0.560–3.435), and prior tracheostomy (OR: 1.102, 95% CI: 0.344–3.527); however, no statistical differences were observed. Although colistin use could not be proven in multivariate analysis, the possibility of being a risk factor cannot be ruled out.