The modulation of rifampin action against Staphylococcus epidermidis biofilms by drug additives to peritoneal dialysis solutions.

Many drugs are added to peritoneal dialysis solutions in continuous ambulatory peritoneal dialysis (CAPD) patients, principally during episodes of peritonitis when antibiotics and nonantibiotic agents are often administered together. To evaluate the influence of nonantibiotic drug additives on antibiotic action, we determined the effect of ten drug additives on the antimicrobial activity of rifampin against S. epidermidis biofilms. None of the additives had any direct effect on biofilm bacteria. While five additives did not affect rifampin action, the other five strongly antagonized rifampin. Insulin and heparin were among these five antagonists. This antagonism suggests that a significant degree of inhibition of antibiotic action may occur by the coadministration of agents in the treatment of peritonitis, particularly in diabetic patients.