Treatment of Carbapenem-Resistant Acinetobacter Baumannii Infections: Which Outcome Is Better, Polymyxin Monotherapy or Combination Therapy?

Infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) are difficult to treat, especially when associated with COVID-19. The use of polymyxins as monotherapy or in combination has been the last resort. The objective was to evaluate antimicrobial treatment based on Polymyxin B (PMB) for CRAB infections and patient outcomes during the COVID-19 pandemic. A retrospective observational study conducted in a teaching hospital in southern Brazil between August 2020 and December 2021, with analysis of electronic medical records. Treatment with PMB was prioritized, and only patients without infection by another agent seven days before or after CRAB isolation were included. A total of 129 patients with CRAB infections were included, of whom 27 met all inclusion criteria. Among these 27 patients, the mean age was 54 years, and 63% had COVID-19. Of all patients infected with CRAB, 48.1% died; when infection was associated with COVID-19, mortality was 47%. CRAB was isolated in 77.8% of tracheal secretions, followed by urine and blood cultures. APACHE II score calculation was possible for 88.8% (24/27) of patients. On the first day of treatment, the mean APACHE score was 21.6, decreasing to 21.5 on day five. On day seven, the mean APACHE score was 19, increasing to 19.9 on day nine. Fourteen-day survival varied according to the therapy applied. Among patients receiving PMB monotherapy, 69.2% (9/13) survived, whereas among those receiving combination therapy with polymyxin and meropenem (PMB+MEM), only 33.3% (4/12) survived. The mean initial APACHE score for PMB monotherapy and PMB+MEM combination therapy was 21.7 and 21.6, respectively. Two patients received polymyxin plus ampicillin/sulbactam, with or without MEM, and survived. CRAB infections resulted in high mortality regardless of the presence of coronavirus. The choice of therapy was essential to improve patient survival, with significant superiority of PMB monotherapy compared to PMB+MEM. Rapid diagnosis, together with optimization and individualization of available antimicrobial therapy, is essential for therapeutic success, even in infections caused by CRAB.