ObjectivesAntimicrobial resistance is a global pandemic that poses a major threat to vision health as ocular bacteria, especially methicillin-resistant S. aureus (MRSA), are becoming increasingly resistant to first-line therapies. Here we evaluated the antimicrobial activity of new synthetic lincosamides in comparison to currently used antibiotics against clinical ocular MRSA isolates. MethodsAntimicrobial susceptibility testing was performed by broth microdilution for two novel synthetic lincosamides (iboxamycin and cresomycin) and 8 comparator antibiotics against a collection of 50 genomically characterized ocular MRSA isolates, including isolates harboring erm genes (n=25). ResultsBoth drugs were active against widespread MRSA clonal complexes CC8 and CC5. The MIC50 and MIC90 of iboxamycin were 0.06 mg/L and 2 mg/L respectively. Cresomycin (MIC50 = 0.06 mg/L) also displayed good activity with an in vitro potency 4-fold higher (MIC90 = 0.5 mg/L) than iboxamycin. In isolates harboring erm genes, MIC90 were >16, 2 and 0.5 mg/L for clindamycin, iboxamycin and cresomycin, respectively. The in vitro potencies of iboxamycin and cresomycin were similar or higher than that of comparator agents and were not impacted by multidrug resistance phenotypes or by the presence of erm genes when compared to clindamycin. ConclusionsOur results demonstrate that iboxamycin and cresomycin display potent in vitro activity against ocular MRSA isolates, including multidrug-resistant isolates harboring erm genes.