Rationale:

• A total of 126,000 hospitalized patients are infected by MRSA annually.
• Over 5,000 patients die as a result of these infections.
• Over $2.5 billion excess health care costs are attributable to MRSA infections.

Evidence:

• After a positive culture of MRSA was obtained from the anterior nares, 48.8% of patients remained colonized for 1 year and 21.2% for 4 years. The presence of a break in the skin, especially a pressure ulcer, predicted continued colonization (24).
• A study examining the cost-effectiveness of active surveillance cultures and barrier precautions for controlling MRSA in the neonatal intensive care units of two tertiary care hospitals found that the cost of identifying colonized patients and implementing effective preventive controls was justified (4).
• A randomized, controlled trial of chlrohexidine gluconate for washing, intranasal mupirocin, and rifampin and doxycycline vs. no treatment for the eradication of MRSA found that treatment with this regimen for 7 days was safe and effective in eradicating MRSA colonization in hospitalized patients for at least 3 months (25).
• A prospective study of 812 soldiers reported that although colonization by MRSA may be less common than that due to MSSA strains, MRSA skin and soft tissue infection was 10 times more frequent in the soldiers colonized by MRSA compared with those colonized by MSSA strains (26). A further study of 3447 soldiers found that 134 were colonized with MRSA, 39 of whom developed MRSA abscesses. Fifty-three percent of the colonizing strains of MRSA were USA300, whereas 97% of the abscess strains were USA300. USA300 strains contained PVL, arginine catabolic mobile element, and type IV staphylococcal cassette chromosome mec (27).
• A review discusses decolonization of MRSA (28).
• Topical nasal application of mupirocin ointment is the most effective treatment for eradicating MRSA colonization (90% in 1 week and 60% over several months). Mupirocin resistance developed in 1% of mupirocin-treated patients and 9% of those receiving oral antimicrobial agents, in addition to mupirocin. For patients with skin lesions, mupirocin-resistant strains, or positive cultures from extra-nasal sites, oral administration of rifampin with a second active antimicrobial agent is recommended in addition to mupirocin nasal treatment (29).
• The Centers for Disease Control and Prevention has published guidelines for the management of multi-drug resistant organisms in health care settings.
• The Society for Healthcare Epidemiology of America published a guideline for preventing nosocomial transmission of multidrug-resistant strains of S. aureus (2).

Comments:

• Although patients colonized with S. aureus appear to have a higher infection rate than noncolonized patients (30), noncarriers have a higher subsequent mortality rate than carriers (31). This latter study suggests that colonization may provide protection from severe complications in patients who develop subsequent infection. It also suggests that antistaphylococcal vaccines may offer some benefit.
• One coagulase-negative staphylococcus, S. lugdunensis, behaves more like S. aureus than a coagulase-negative staphylococcus; however, its sites of colonization differ. Whereas S. aureus preferentially colonizes the nose, S. lugdunensis preferentially colonizes the groin and the lower extremities, especially the nail bed of the first toe. The difference in niches that these two staphylococci inhabit has implications for rapid identification on admission of patients who may be colonized by staphylococci (32).