In vitro and in vivo activity of eravacycline against Mycobacterium abscessus

Eravacycline is a fluorocycline antibiotic with activity against multidrug-resistant Gram-negative bacteria. However, its activity against Mycobacterium abscessus (MAB) has not been fully evaluated. This study aimed to evaluate the in vitro and in vivo activity of eravacycline against MAB. The in vitro activity of eravacycline against 73 MAB isolates was evaluated by broth microdilution to determine minimal inhibition concentrations (MICs). For in vivo assessment, a BALB/c nude mouse model was established via intravenous infection with MAB, resulting in systemic dissemination of bacteria. Outcomes were evaluated based on bacterial burden in the lungs and spleens and histopathological analysis. In this study, eravacycline demonstrated low MIC values against MAB isolates, with MIC₅₀ and MIC₉₀ values of 0.0625 mg/L and 0.125 mg/L, respectively. It exhibited lower MIC values compared with tigecycline (MIC₅₀: 1 mg/L; MIC₉₀: 2 mg/L), minocycline (MIC₅₀: > 8 mg/L; MIC₉₀: > 8 mg/L), and clarithromycin (MIC₅₀: 0.5 mg/L; MIC₉₀: > 16 mg/L). In vivo, eravacycline treatment (5 mg/kg) reduced bacterial loads in the lungs and spleens of infected mice; however, lung involvement in this model reflects systemic dissemination rather than primary pulmonary infection. In conclusion, eravacycline exhibits in vitro and in vivo activity against MAB under the tested experimental conditions.