Combined effect of eravacycline and omadacycline with other antimicrobial agents against Acinetobacter Baumannii

The increasing prevalence of multidrug-resistant Acinetobacter baumannii has significantly limited available treatment options and highlights the need for effective combination therapies. Novel Tetracycline derivatives such as eravacycline and omadacycline may represent promising alternatives against resistant A. baumannii isolates. This study aimed to evaluate the in vitro Antibacterial activities of these agents and to investigate their potential synergistic interactions with selected antimicrobial agents. The Antibacterial activities of eravacycline, omadacycline, ceftazidime, meropenem, tobramycin, ciprofloxacin, and colistin were determined against 50 clinical isolates using the broth microdilution method. Synergistic interactions between eravacycline or omadacycline and five antimicrobial agents were evaluated in 10 meropenem-resistant isolates (MIC ≥ 8 µg/mL) by the checkerboard assay. Eravacycline and omadacycline demonstrated low MIC values against the tested isolates. Synergistic interactions were frequently observed, particularly in combinations with ceftazidime, meropenem, and colistin. Eravacycline and omadacycline showed promising in vitro activity both alone and in combination with conventional antimicrobial agents. These findings suggest that further studies are needed to clarify their potential role in the treatment of resistant Acinetobacter baumannii infections.