Background: The emergence of multidrug-resistant Acinetobacter baumannii has led to the re-use of colistin. Colistin-resistant A. baumannii [CRA] was rare but is being reported more often now.

Objective: To explore the factors associated with CRA.

Materials and Methods: A retrospective case-control study has conducted. The medical records of 20 patients with CRA and 80 patients with colistin-susceptible A. baumannii [CSA] were reviewed.

Results: Univariate analysis showed that presence of five co-morbidities, intensive care unit stay, prior use of colistin, duration of colistin use, and some prior antibiotics were associated with CRA (p<0.05). However, using multivariate analysis, prior colistin and meropenem use had adjusted odds ratios [AOR] of 21.04; 95% CI of 3.11 to 142.32 (p = 0.002) and 13.54; 95% CI of 1.15 to 159.64 (p = 0.038), respectively, for CRA. Colistin duration (days) was significantly associated with resistance (AOR 1.22, 95% CI of 1.04 to 1.44, p = 0.013).

Conclusion: These results should increase awareness of appropriate colistin administration i.e., the duration of colistin used.

Keywords: Acinetobacter baumannii, Colistin-resistant, Antibiotic used, Resistant factors, Polymyxin