Risk Factors of Carbapenem-resistant Acinetobacter baumannii Infection among Hospitalized Patients

Objective: A very common pan-resistant pathogen in health care-related infections in Taiwan is carbapenem-resistant Acinetobacter baumannii (CRAB), which can increase mortality and health care expenses. Increased resistant bacteria due to increased antimicrobial consumption may be responsible for the soaring percentage (to 70%) of the CRAB infection rate in hospitalized patients. In the present study, we used a case-case-control study in a teaching hospital to investigate factors (especially the prior use of antimicrobials) that affect the development of A.baumannii resistance. Methods: This was a case-case-control design and was composed of two parallel age- and sex-matched control groups, and two experimental groups [i.e., the carbapenem-resistant group (n=73) and the carbapenem-sensitive group (n=77)]. The primary outcome was to identify common risk factors that induce CRAB in hospitalized patients in a teaching hospital in Taiwan. Results: The common risk factors for infection of patients by CRAB and carbapenem-sensitive A.baumannii (CSAB) were previous antimicrobial exposure to piperacillin/tazobactam [odds ratio (OR), 2.5] and amikacin (OR, 2.5), meropenem-treated patients had a 4.99-fold increased risk of CRAB infection, but not CSAB infection, when they were admitted to the hospital within 3 months after the antimicrobial exposure. Diabetic patients were moreover prone to being infected by both CRAB and CSAB with an increased OR of 6.26. Ventilator use increased the OR significantly in CRAB infections and CSAB infections by 13.51-fold and 4.72-fold, respectively. Conclusion: This study confirms that prior use of antimicrobials such as piperacillin/tazobactam and amikacin can significantly increase CRAB and CSAB infections in hospitalized patients. The prior use of meropenem increased CRAB infections, but not CSAB infections, in patients who were hospitalized 3 months after the drug exposure. Diabetes and ventilator use were also associated with a high rate of CRAB and CSAB infections.