Health & Medical Pregnancy & Birth & Newborn

Epidemiology of MSSA and MRSA in a Neonatal Intensive Care Unit

Epidemiology of MSSA and MRSA in a Neonatal Intensive Care Unit

Abstract and Introduction


Objective: To assess the epidemiology of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) infections in a neonatal intensive care unit (NICU).
Study Design: A retrospective chart review was conducted from 2000–2007; demographic and clinical characteristics of infected infants and crude mortality were assessed.
Results: During the study period, there were 123 infections caused by MSSA and 49 infections caused by MRSA. Although the types of infections caused by MSSA and MRSA were similar, infants with MRSA infections were younger at clinical presentation than infants with MSSA infections (P=0.03). The overall rate of S. aureus infections was approximately 15–30 per 1000 patient-admissions. The rate of bacteremia and skin and soft tissue infections remained stable over time. Among extremely low birth weight infants (birth weight <1000 g), 4.8 and 1.8% developed an infection caused by MSSA or MRSA, respectively. Infections occurred in a bimodal distribution of birth weight; 53% of infections occurred in extremely low birth weight infants and 27% occurred among term infants birth weight ≥2500 g, many of whom underwent surgical procedures.
Conclusions: MSSA and MRSA remain significant pathogens in the NICU, particularly for extremely premature infants and term infants undergoing surgery. Further work should investigate infection control strategies that effectively target the highest risk groups and determine if vertical transmission of MRSA is responsible for the younger age at presentation of infection.


Staphylococcus aureus is a well known pathogen among infants hospitalized in the neonatal intensive care unit (NICU). However, there are few recent data estimating the rate of infections caused by S. aureus or describing clinical presentations, including potential differences in the clinical presentations of methicillin-susceptible S. aureus (MSSA) versus methicillin-resistant S. aureus (MRSA), particularly in the era of community-acquired MRSA strains. Thus, we sought to determine potential changes in the epidemiology of infections caused by MSSA and MRSA in our NICU from 2000–2007.

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