Non-tuberculous mycobacterial infections are gradually increasing worldwide, with slow-growing mycobacteria such as Mycobacterium avium, Mycobacterium intracellulare and Mycobacterium kansasii accounting for the majority of cases. The use of tetracyclines has received renewed attention in recent years, and this study was designed to investigate the antibacterial activity of omadacycline, eravacycline, tigecycline, sarecycline, minocycline and doxycycline against M. avium, M. intracellulare and M. kansasii. Susceptibility testing of six tetracyclines was conducted against M. avium, M. intracellulare and M. kansasii isolates, and all the clinical isolates were collected from January 2012 to December 2018. All six agents exhibited poor antibacterial activity against slowly growing mycobacteria (SGM) isolates of three subspecies with MIC 50 and MIC 90 ≥8 μg/mL. M. intracellulare and M. kansasii had lower resistance rates to omadacycline than the other five drugs. The severe resistance of SGM to tetracycline suggests that developing tetracycline-class antibiotics needs to overcome existing resistance mechanisms.

Therapeutic options for Mycobacterium abscessus infections are extremely limited, and new drugs are needed. The anti- M. abscessus activity of MRX-6038,

The antimicrobial activities of four third-generation tetracycline-class drugs, omadacycline (OMC), eravacycline (ERC), tigecycline (TGC), and sarecycline (SAC), were determined for 193 M. abscessus isolates. The activities of the four drugs at two different temperatures (30°C and 37°C) were also tested.