Activity of quinupristin/dalfopristin against Staphylococcus epidermidis in biofilms: A comparison with ciprofloxacin

Bactericidal effects of quinupristin/dalfopristin and ciprofloxacin have been studied against six strains of Staphylococcos epidermidis, with varying erythromycin resistance phenotypes and varying abilities to form slime and adhere, growing as biofilms. Ciprofloxacin and quinupristin/dalfopristin killed (2-3 log(10) cfu/mL) planktonic and sessile cells slowly, but progressively, over the course of 48 h. Rates of killing by quinupristin/dalfopristin were independent of concentration over the range 5-30 mg/L, and were somewhat slower than those seen with ciprofloxacin. These findings suggest that quinupristin/dalfopristin may be useful in the treatment of line-associated infections.