The impact of topical antibiotic for eradication of MSSA and/or MRSA is best known for mupirocin, a compound synthesized by Pseudomonas fluorescens that inhibits bacterial protein synthesis by reversibly binding to bacterial isoleucyl-tRNA synthetase. Several studies have demonstrated the efficacy of mupirocin for the eradication of MRSA and MSSA in different populations (Laupland and Colby 2003). Its effect in healthy healthcare workers (Doebbeling et al. 1993, Fernandez et al. 1995, Reagan et al. 1991, Scully et al. 1992) may be particularly relevant for prevention in surgical patients. By pooling six double-blind, randomized studies in 339 healthcare workers who carried S. aureus in their nose, Doebbeling et al. reported that the application of mupirocin twice daily for 5 days eradicated 91% of participants, compared with 6% of those who received a placebo. No emergence of resistance to mupirocin was observed (Doebbeling et al. 1993).
Early studies in the surgical setting were promising, showing not only decolonization, but also significantly lower SSI rates among patients who received preoperative intranasal mupirocin treatment compared with historical controls (Cimochowski etal. 2001, Gernaat-van der Sluis etal. 1998, Kluytmans etal. 1996). More recently, Perl et al. published a double-blind, randomized, placebo-controlled trial that included 4030 patients who underwent general, gynecologic, neurological, or cardiothoracic surgery (Perl et al. 2002). Mupirocin was administered intranasally twice per day for up to 5 days before surgery. The rate of S. aureus SSI in mupirocin recipients (2.3%) was not significantly different from that in placebo recipients (2.4%). However, in the secondary analysis of 891 nasal carriers of S. aureus (22%, proportion of MRSA not reported), significantly fewer mupirocin-treated patients developed surgical and nonsurgical nosocomial S. aureus infections (4%) compared with patients who received placebo (7.7%). This reduction was significant (OR for infection 0.49, 95%CI 0.25-0.92). Mupirocin was also more frequently associated with decolonization (84% versus 27%) although only 83% of the patients received three doses or more. The rate of resistance to mupirocin was low (0.6% of 1021 isolates).
A smaller double blind, randomized, placebo-controlled trial was conducted in 614 patients undergoing elective orthopedic surgery with insertion of implant material (Kalmeijer et al. 2002). Mupirocin or placebo was given intranasally twice a day the day before surgery and the day of surgery. As in Perl's study, S. aureus SSI rates were similar in the mupirocin group (3.8%) and the placebo group (4.7%) despite a higher eradication rate with mupirocin (84%, compared with 22% in placebo recipients). Furthermore, the incidence of S. aureus SSIs was similar in both groups.
In conclusion, data available to date do not support routine administration of prophylactic intranasal mupirocin to prevent SSI. Subgroup analyses have suggested a small reduction of S. aureus infections—thus presumably of MRSA infections as well—in patients who carry this bacterium. This benefit, which still needs confirmation, would require the identification of MRSA carriers, a topic that will be addressed below in the section on infection control measures.
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