Spa Typing of Staphylococcus aureus in a Neonatal Intensive Care Unit During Routine Surveillance

Abstract

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.

Genomic and Epidemiological Features of Two Dominant Methicillin-Susceptible Staphylococcus aureus Clones from a Neonatal Intensive Care Unit Surveillance Effort

“…As previously reported, colonization by MSSA (13.6%) was markedly higher than colonization by MRSA (2.4%) ( 18 ). Of the diverse MSSA staphylococcal protein A ( spa )-types identified during the surveillance period, t279, t1451, and t571 were highly prevalent, accounting for almost one-third of NICU MSSA isolates ( 18 ). MSSA sequence type 398 (ST398), encompassing spa -t1451 and t571, has been identified in populations within Europe, China, the Caribbean, and New York, specifically, northern Manhattan ( 19 – 25 ).…”

“…Study flowchart. A previously published study by Grohs et al ( 18 ) assessed the use of surveillance swabs to identify MSSA colonization and diversity in neonates over an 18-month period, January 2017 to June 2018. During the surveillance period, 1,556 infants were admitted to the NICU.…”

“…During the surveillance period, eligible infants with positive MSSA or MRSA surveillance cultures were decolonized with mupirocin applied to the anterior nares and/or chlorhexidine baths ( 18 ). Infants with mupirocin-resistant isolates did not receive mupirocin.…”

“…We recently undertook a surveillance effort to elucidate the prevalence and diversity of S. aureus colonization in a level III to IV NICU located in northern Manhattan, NY ( 18 ). As previously reported, colonization by MSSA (13.6%) was markedly higher than colonization by MRSA (2.4%) ( 18 ).…”

“…We recently undertook a surveillance effort to elucidate the prevalence and diversity of S. aureus colonization in a level III to IV NICU located in northern Manhattan, NY ( 18 ). As previously reported, colonization by MSSA (13.6%) was markedly higher than colonization by MRSA (2.4%) ( 18 ). Of the diverse MSSA staphylococcal protein A ( spa )-types identified during the surveillance period, t279, t1451, and t571 were highly prevalent, accounting for almost one-third of NICU MSSA isolates ( 18 ).…”