Single step high rifampin resistance in clinical isolates of methicillin-resistant staphylococcus aureus and its prevention by erythromycin combination

ABSTRACT

The emergence of resistance to the potent antistaphylococcal antibiotic rifampin [RIF] has been investigated against 6 methicillin- and ampicillin-resistant Staphylococcus aureus clinical isolates using turbidimetric and viable count techniques. Single step high level resistance was developed rapidly due to induction of mutants resistant to suprapharmacological levels [1000 times the minimum inhibitory concentration, MIC] of RIF irrespective of the concentration of RIF present. Erythromycin [ERY] at an MIC level effectively prevented RIF resistance. Thus, the RIF-ERY combination warrants further evaluation in the therapy of staphylococcal infections, especially those resistant to B-lactam antibiotics