Novobiocin and rifampicin in combination against methicillin-resistantStaphylococcus aureus: anin-vitrocomparison with vancomycin plus rifampicin

摘要

Novobiocin and rifampicin were evaluatedin vitroas a possible new antibiotic combination against methicillin-resistantStaphylococcus aureus. An evaluation of 20 strains of methicillin-resistantStaph. aureususing microdilution checkerboard techniques at 105cfu/ml showed neither synergy nor antagonism between novobiocin and rifampicin or between vancomycin and rifampicin. Agar surface inoculation of six strains of methicillin-resistantStaph. aureusshowed increased synergy with increased inocula (106−109cfu) for novobiocin plus rifampicin compared to vancomycin plus rifampicin. Time-kill curves showed indifference at 6 h for all combinations, whereas, at 24 and 48 h, they generally showed indifference, occasionally synergy, but never antagonism. The‘synergy’between novobiocin and rifampicin at higher inocula of methicillin-resistantStaph. aureusappears to be due to prevention of emergence of resistant organisms and may have clinical relevance. The combination of novobiocin-rifampicin merits further investig