Monotherapy versus combination therapy for treatment of carbapenem-resistant Acinetobacter baumannii complex infections: results from an observational study.

OBJECTIVE

To evaluate the efficacy of monotherapy versus combination therapy in the treatment of carbapenem-resistant Acinetobacter baumannii infections.

METHODS

A retrospective observational study was conducted in two tertiary hospitals in Brazil from 2018 to 2022. Patients diagnosed with bloodstream infections or ventilator-associated pneumonia caused by carbapenem-resistant Acinetobacter baumannii were included. Data on demographics, clinical characteristics, antimicrobial regimens, and outcomes were collected. Statistical analyses, including multivariate logistic regression, were performed to identify predictors of mortality.

RESULTS

Among 123 patients (median age: 61 years), 86.2% were treated in the intensive care unit, 28-day mortality was 59,3%, and the overall mortality was 73.2%. Combination therapy was more frequently used (75.6%) and typically involved polymyxin-based regimens (71.5%). Sulbactam-containing regimens were employed in 16.3% of cases. Monotherapy was more common in ventilator-associated pneumonia (33.3%) than in bloodstream infections (14%). Mortality rates were similar between monotherapy and combination therapy (73.3% versus 73.1%; p = 0.982). In the multivariable logistic regression model, only the APACHE II score (OR = 1.12; 95%CI 1.05 - 1.21; p = 0.001) remained independently associated with mortality. Sulbactam-based therapy was not independently associated with survival (OR = 0.80; 95%CI 0.22 - 2.85; p = 0.725).

CONCLUSION

Our findings suggest that neither monotherapy nor combination therapy is associated with lower mortality in this cohort of carbapenem-resistant Acinetobacter baumannii infections, likely due to the severity of the baseline illness. Further prospective studies are needed to confirm these results and refine treatment guidelines.