Extensive drug resistant Acinetobacter baumannii: a comparative study between non-colistin based combinations

Background The Gastrointestinal Surgery Center (GISC)-Mansoura University, faced a series of extensive drug resistant (XDR) A. baumannii cases, that were microbiologically resistant to penicillins, cephalosporins, fluoroquinolones, aminoglycosides, carbapenems and tigecycline. Colistin would have been a last resort therapy in such situation, however, intravenous polymyxins E (colistin) is relatively unavailable in Egypt. Many practitioners tried to form antibiotic combinations from the available antibiotics to overcome the resistance mechanisms of the pathogen. Objective Evaluate the clinical outcomes of these combinations retrospectively. Setting The study took place at the GISC, which is an academic specialized center affiliated with Mansoura University-Egypt. Method Clinical data were collected from the patients' files, where the subjects were classified into two major groups according to the therapeutic intervention. Group 1 included 24 patients divided into 4 subgroups. The first was treated by a Cephalosporin with a Fluoroquinolone (1A), The second was treated by a Carbapenem with a Fluoroquinolone (1B), The third was treated by a B-lactam with an Aminoglycoside (1C) and the fourth was treated by Carbapenem with a Glycylcycline (1D). Group 2 included 6 patients, treated with Tigecycline and Ampicillin-Sulbactam. Main outcome measure Primary outcomes are the A. baumannii microbiological culture negativity after 14 days of therapy and the 30 days' survival after the antibiotic course, while the secondary outcomes are the expected therapies' side effects. Results Group 2 is associated with significant higher primary outcomes without a significant difference regarding the secondary outcomes. Conclusion The combination of Tigecycline and Ampicillin-Sulbactam, appears to be a clinically effective therapy against XDR A. baumannii, despite each agent being resistant alone, without alerting adverse effects.