Clinical characterization of patients with carbapenem-resistant versus carbapenemsusceptible Acinetobacter baumannii infections

Abstract

Background: Steady rise in carbapenem resistance in Acinetobacter baumannii has become a major challenge for clinicians. The objective of this study is to characterize clinical features of infections secondary to carbapenemresistant organisms compared to carbapenemsusceptible organisms. Methods: We conducted a retrospective analysis of data for 39 patients from two tertiary care medical centers who had positive cultures for A. baumannii. Collected data included clinical presentations, underlying illnesses, treatment course, clinical outcome, microbiological data and other laboratory data. Statistical comparisons were done between patients infected with carbapenem-resistant (CRAB) and carbapenem-susceptible (CSAB) isolates using Fisher's exact test and Student's T-test. Multidrug resistance (MDR) was defined as resistance to more than two classes of antibiotics generally active against A. baumannii. Results: Total 17 (44%) patients had carbapenemresistant (CRAB) and 24 (62%) had multidrug resistant (MDR) A. baumannii. Mean age (5.3(plus or minus)5.7 years) and male predominance (70%) were comparable in both groups. Predisposing factors included diabetes mellitus (15), pressure ulcers (12), malignancy (8), paraplegia (7), burn (5), peripheral vascular disease (5), and chronic renal failure (5). Majority of the infections involved wound (13) and bone (10) followed by sputum (8), urine (5) and bloodstream (3). Mean duration for first positive A. baumannii cultures after admission to the hospital was 6.6 ((plus or minus) 3.4) days. Patients infected with CRAB had significantly higher rates of respiratory or other organ failures (47% vs. 14%, p < 0.05), and were more frequently admitted to the intensive care unit (53% vs. 18%, p < 0.05), compared to the patients with CSAB. Patients with CRAB were also more likely to be admitted for prolonged durations in the hospital (mean = 31.5 vs. 8.5 days, p < 0.01) and in the intensive care unit (mean = 25.9 vs. 1.2 days, p < 0.05). Mortality was significantly higher among patients with CRAB compared to those with CSAB (29% vs. 4.5%, p < 0.01). A. baumannii infections were treated for an average duration of 24 ((plus or minus)7) days. Antibiotics used for treatment included carbapenems, ampicillin-sulbactam, tigecycline, aminoglycosides, colistin and polymyxin B. Conclusion: Carbapenem-resistant A. baumannii infections were associated with severe morbidity, requiring prolonged hospitalization and ICU admissions, and also resulted in increased mortality.