Emergence of resistance in staphylococci after long-term mupirocin application in patients on continuous ambulatory peritoneal dialysis.

In the present study, we evaluated the effects of once-weekly mupirocin application to catheter exit sites on Staphylococcus aureus and coagulase-negative staphylococcus (CNS) colonization and investigated the resistance of those bacteria to methicillin (MeR) and mupirocin (MuR). We enrolled 36 continuous ambulatory peritoneal dialysis (CAPD) patients (mean age: 55.1 +/- 1.4 years) into the study. The patients (men/women: 21/15) had been applying mupirocin to the catheter exit site once weekly before the start of the study (mupirocin treatment duration: 3.1 +/- 2.0 years). During the study period, swabs were taken monthly from the nares, axillae, inguinal area, and catheter exit site. The swabs were inoculated on blood plates. Methicillin and mupirocin susceptibility were tested by disc diffusion according to the interpretative criteria of the National Committee for Clinical Laboratory Standards. We evaluated a total of 144 cultures. Among CNS isolates, the MuR was 66%, and the MeR was 38.8%. At the start of the study period, 3 patients were S. aureus nasal carriers. In nasal swabs, no MeR S. aureus was identified, and only 1 MuR S. aureus was found. Once-weekly application of mupirocin at the exit site in CAPD patients led to comparable rates of colonization by MuR S. aureus as did thrice-weekly or more frequent application. Clinical results showing high mupirocin and methicillin resistance in CNS are controversial.