Omadacycline invitro activity against a molecularly characterized collection of clinical isolates with known acquired tetracycline resistance mechanisms.

Omadacycline and tigecycline MIC90 values were 2 μg/mL and 0.25 μg/mL, respectively, against Staphylococcus aureus carrying tet(M), whereas the minocycline, tetracycline, and doxycycline values were > 8 μg/mL. Similarly, omadacycline and tigecycline remained active against Enterococcus faecalis and Streptococcus pneumoniae harboring tet(L)and/or tet(M)(MIC90, 0.06-0.25 μg/mL), whereas other tetracyclines were inactive (MIC90, >8 μg/mL). Omadacycline and tigecycline remained more potent than minocycline, tetracycline, and doxycycline against Enterobacteriaceae carrying tet. This study demonstrates the effectiveness of modern tetracyclines, omadacycline, and tigecycline against isolates with tetracycline resistance genes.