Prevalence of and risk factors for methicillin-resistant Staphylococcus aureus colonization and infection among infants at a level III neonatal intensive care unit

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a well-known nosocomial pathogen of neonatal intensive care unit (NICU) patients and can cause both serious infections in preterm neonates and prolonged MRSA outbreaks in NICUs.

Objectives: Our objectives were to determine the prevalence of and identify risk factors for MRSA colonization and infection in the NICU and the impact of an active surveillance program on MRSA in the NICU.

Methods: We collected weekly nasal MRSA surveillance cultures on 2,048 infants admitted to NICU over 3 years. Data on these infants were collected retrospectively. Characteristics of MRSA colonized and infected infants were analyzed and compared.

Results: MRSA colonization was detected in 6.74% of infants, and MRSA infection occurred in 22% of those colonized. Using clinical cultures alone, only 41 (27.5%) of 149 MRSA affected infants were identified. The majority (75%) developed MRSA infection within 17 days of colonization. For every 10-day increment in NICU stay, the odds ratio of being infected and colonized with MRSA increased by 1.32 and 1.29, respectively. Colonization was significantly associated with longer NICU stay, low birth weight, low gestational age, and multiple gestation status.

Conclusion: Colonization is a risk factor for infection with MRSA in NICUs. Clinical cultures underestimate MRSA affected infants in NICUs, whereas active surveillance cultures could detect MRSA affected infants earlier and limit nosocomial spread.