SAN DIEGO, CA— Use of intranasal mupirocin as a strategy to prevent methicillin-resistant Staphylococcus aureus (MRSA) in the neonatal intensive care unit (NICU) is limited by a 50% recolonization rate in some high-risk neonates, reported Sara M. Wittig, MPH, CIC, from Johns Hopkins Hospital, Baltimore, MD, at IDWeek 2012.

Currently, there is limited longitudinal data available on the effectiveness of intranasal mupirocin to eradicate colonization and reduce the morbidity and mortality caused by MRSA infections. Study investigators analyzed data on 3,632 patients that were admitted for a total of 66,695 days from 2007–2011. Infants with a culture growing MRSA were treated with intranasal mupirocin, and some infants received 2% chlorhexidine gluconate baths. Infants were monitored for recurrent MRSA colonization, and clinical cultures growing MRSA were investigated to identify infections meeting the National Healthcare Safety Network (NHSN) criteria.

Of the total patients, 74 infants grew MRSA, including 66 (89.2%) neonates identified as colonized and 8 neonates (11%) with a MRSA infection that predated identification of MRSA colonization. Of the 66 MRSA colonized infants, 37 (56%) received intranasal mupirocin. Infants that did not receive it had a shorter median time to discharge than those that did receive it (4 days vs. 26 days, P=0.05).

Half of the neonates who received intranasal mupirocin and remained in the NICU for ≥21 days became recolonized with MRSA. From the initial 66 colonized neonates, 11 developed an infection. Overall, there was no difference in the risk of infection in those who did and did not receive intranasal mupirocin (hazard ratio 0.66; 95% confidence interval 0.19–2.37).

Wittig and her team concluded that in this setting, “despite an aggressive screening and decolonization program, MRSA infections still occurred.” A total of 16% of patients treated with intranasal mupirocin still developed MRSA, and 42% of all infections preceded identification of intranasal colonization.

They noted that further randomized studies are needed determine efficacy of intranasal mupirocin and to identify other adjuvant strategies to prevent MRSA infections in neonates.