Dose-ranging study to assess the application of intranasal 2% mupirocin calcium ointment to eradicate Staphylococcus aureus nasal colonization.

BACKGROUND: Mupirocin nasal ointment may be prescribed for decolonization prior to surgical procedures, especially for carriers of methicillin-resistant Staphylococcus aureus (MRSA). The approved regimen for decolonization of S. aureus from the anterior nares is twice daily for 5 d (10 doses). We performed a two-center, randomized, open-label study to compare the utility of six and 10 doses for decolonization of S. aureus. METHODS: Patients expecting to undergo surgery were screened for S. aureus nasal carriage approximately three weeks prior to the procedure. Those found to be positive were offered enrollment in the study. In the first arm (n=41), patients were randomized to receive 2, 3, or 5 d (six or 10 doses) of treatment prior to their operation. Their anterior nares were swabbed for culture and S. aureus polymerase chain reaction (PCR) during the decolonization therapy period as well as for four weeks after surgery. In the second arm (n=60), all patients were given 5 d (10 doses) of nasal mupirocin treatment, and the patient's anterior nares were swabbed for culture and S. aureus PCR for four weeks after surgery. Data from six of the patients were excluded from analysis because of failure to submit swabs after operation. All S. aureus isolates were tested for susceptibility to mupirocin and the presence of the mecA gene to detect MRSA. RESULTS: In Arm 1, 16 patients received 10 doses of mupirocin, 18 received six doses (twice daily for 3 d), and 7 received six doses (thrice daily for 2 d). In the second arm, all patients received 10 doses of mupirocin (twice a day for 5 d). Overall, 89.5% patients who received 10 doses of mupirocin remained decolonized for at least four weeks after surgery versus 68.0% of patients who received six doses (p=0.016). There was no difference between arms 1 and 2 for those given mupirocin twice daily for 5 d. CONCLUSION: The ten-dose regimen is superior to any six-dose regimen for de-colonizing S. aureus from the anterior nares of patients and for maintaining the decolonized state for at least four weeks after therapy.