The in vitro activities of rifampin, rifabutin, rifapentine, and rifaximin were tested against 200 periprosthetic joint infection (PJI)-associated staphylococci. Seven rifampin-resistant isolates had MICs of ≥4 μg/ml. Three isolates had rifampin MICs of 0.25 to 1 μg/ml and harbored an Asp471Gly RpoB variant, suggesting that the CLSI rifampin-susceptible staphylococcal breakpoint of ≤1 μg/ml may be too high. The remaining isolates had rifampin MICs of ≤0.016 μg/ml, and the rifampin, rifabutin, rifapentine, and rifaximin minimum biofilm bactericidal concentrations (MBBC) for ≥50% of isolates were 8, 1, 2, and 4 μg/ml (for S. aureus) and 2, 0.06, 0.25, and 0.5 μg/ml (for S. epidermidis), respectively, for rifampin-susceptible isolates. Nonrifampin rifamycins have promising staphylococcal activity, including antibiofilm activity.
Keywords: Staphylococcus aureus; Staphylococcus epidermidis; biofilm; periprosthetic joint infection; rifabutin; rifampin; rifamycins; rifapentine; rifaximin; rpoB.
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