Sub-growth-inhibitory concentrations of omadacycline inhibit Staphylococcus aureus haemolytic activity in vitro

OBJECTIVES: To evaluate the effect of sub-growth-inhibitory concentrations of omadacycline on Staphylococcus aureus ATCC 10832 haemolytic activity in vitro. METHODS: Following determination of the MICs of omadacycline and comparator antibiotics, the strain was grown in the presence of individual antibiotics and the percentage of haemolysis assayed; ‘washout’ experiments were performed with omadacycline only. RESULTS: Omadacycline inhibited S. aureus haemolytic activity in vitro at sub-growth-inhibitory concentrations. Inhibition was maintained at least 4 h after removal of extracellular drug. CONCLUSIONS: Omadacycline’s in vitro potency and suppression of virulence factors might contribute to its efficacy in the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia caused by virulent strains of S. aureus. This finding could be relevant for other organisms and virulence factors that depend on new protein synthesis.