Mupirocin resistance after long-term use for Staphylococcus aureus colonization in patients undergoing chronic peritoneal dialysis.
Mupirocin (Mup) has been used extensively to prevent Staphylococcus aureus (SAu) infections in patients undergoing peritoneal dialysis (PD). Resistance to Mup has been reported, but its relevance after long-term use of this drug in PD is unknown. Colonization by SAu was treated with topic Mup in our unit between September 1990 and December 2000. Sensitivity to Mup was tested in 437 strains of SAu isolated from 155 PD patients and 62 dialysis partners. Resistance to Mup was classified as low (minimal inhibitory concentration [MIC] > or = 8 microg/mL) or high (MIC > or = 512 microg/mL) degree. MIC90 was 0.125 microg/mL in 1990 to 1996 (5% low, 0% high-degree resistance), 64 microg/mL in 1997 to 1998 (6.6% low, 8.3% high-degree resistance), and 1,024 microg/mL in 1999 to 2000 (2.3% low, 12.4% high-degree resistance). Mup-resistant SAu were isolated from 25 patients and 13 partners a median of 15 months after starting PD. Resistance was associated frequently with repeated treatments of SAu recolonization, but was detected in 3 cases at the start of PD therapy. The accumulated incidence of SAu exit-site infection in the period 1997 to 2000 was 32.3% in patients colonized by Mup-resistant SAu as compared with 14.5% in those colonized by Mup-sensitive SAu (P = 0.03). Mup-resistant SAu have emerged in a significant proportion of our PD patients and dialysis partners. This emergence has resulted in a moderate, but significant, increase in the risk of SAu exit-site infection and raises concerns about the future of Mup as the therapy of choice for SAu colonization in patients undergoing chronic PD.