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Updated: Nov 2, 2025
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Spa Typing of Staphylococcus aureus in a Neonatal Intensive Care Unit During Routine Surveillance
Emily Grohs1,2, Alexandra Hill-Ricciuti2, Nicole Kelly2
1Mailman School of Public Health, Columbia University Irving Medical Center, New York, New York, USA.
Background:
Staphylococcus aureus protein A (spa) typing can be used to expand characterization of the epidemiology of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in neonatal intensive care units (NICU).
Methods:
From January 2017 to June 2018, twice-monthly surveillance for S. aureus was performed in an academically affiliated NICU. Decolonization of infants colonized with S. aureus included chlorhexidine gluconate bathing and/or mupirocin for those with mupirocin-susceptible strains. Spa typing and mupirocin-resistance testing were performed. Demographic and clinical characteristics were compared between infants colonized with MSSA vs MRSA and infants with and without the most common MSSA spa type, MSSA-t279.
Results:
Overall, 14% and 2% of 1556 hospitalized infants had positive surveillance cultures for MSSA and MRSA, respectively. Thirty-six infants harbored unique MSSA spa types, 5 infants harbored unique MRSA spa types, and 30 MSSA and 6 MRSA spa types were identified in ≥2 infants. No outbreaks were identified during the study period. MSSA-t279 was isolated from 3% of infants and largely detected from infants hospitalized in one section of the NICU; 96% of t279 isolates were mupirocin resistant. Infection rates, length of hospitalization, and mortality were similar among infants initially colonized with t279 vs other MSSA spa types.
Conclusions:
The MSSA colonization burden was 5-fold larger than that of MRSA. Numerous unique spa types were identified. The most common spa type, MSSA-t279, was not associated with increased morbidity or mortality but was mupirocin resistant and associated with clustered NICU beds. This suggests potential transmission from the environment, shared staff, and/or workflow issues requiring further study. Other decolonization strategies for S. aureus in the NICU are needed.
Insights
Methicillin-susceptible Staphylococcus aureus (MSSA) colonization is more common than MRSA in NICUs. The prevalent MSSA spa type t279 is mupirocin-resistant and clustered, indicating potential transmission issues needing further investigation.
Area of Science:
- Neonatal Intensive Care Unit (NICU) epidemiology
- Microbial typing and resistance surveillance
- Infection control and prevention
Background:
- Staphylococcus aureus protein A (spa) typing aids in characterizing methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) epidemiology in NICUs.
- Understanding colonization patterns is crucial for infection control in vulnerable neonatal populations.
Purpose of the Study:
- To characterize the epidemiology of MSSA and MRSA colonization in a NICU using spa typing.
- To assess the prevalence and characteristics of the most common MSSA spa type (t279) and its association with clinical outcomes.
Main Methods:
- Twice-monthly surveillance for S. aureus in 1556 hospitalized infants from January 2017 to June 2018.
- Spa typing and mupirocin-resistance testing were performed on S. aureus isolates.
- Comparison of demographic and clinical characteristics between different colonization groups.
Main Results:
- MSSA colonization (14%) was significantly more prevalent than MRSA colonization (2%).
- Numerous unique MSSA and MRSA spa types were identified, with MSSA-t279 being the most common (3%).
- MSSA-t279 isolates were largely mupirocin-resistant and clustered in specific NICU areas, but not associated with increased infant morbidity or mortality.
Conclusions:
- The MSSA colonization burden in the NICU is substantial and diverse, with a notable proportion of mupirocin-resistant strains.
- The clustering of MSSA-t279 suggests potential environmental or workflow-related transmission routes requiring further investigation.
- Novel decolonization strategies are needed to effectively manage S. aureus colonization in the NICU setting.
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