Prolonged outbreak of clonal, mupirocin-resistant methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit: association with personnel and a possible environmental reservoir, analyzed using whole genome sequencing

Published:September 17, 2021DOI:


      • A clonal MRSA can cause a prolonged outbreak in NICU with quiescent periods
      • Whole genome sequencing is a valuable tool for analyzing an MRSA outbreak
      • Healthcare personnel can be implicated in MRSA transmission to infants
      • Room location within a NICU can be associated with MRSA transmission



      Outbreaks of MRSA occur in NICUs and may be difficult to control. We describe an outbreak of mupirocin-resistant MRSA, molecular epidemiology of isolates and control.


      Medical record review of personnel contact with infants. MRSA isolates were analyzed by whole genome sequencing (WGS); single nucleotide polymorphisms (SNPs) were identified.


      A 31-month outbreak of MRSA infection occurred. Weekly colonization surveillance of infants was initiated; initial prevalence was 45%. Isolates exhibited high level mupirocin-resistance. There were 3 periods of increased colonization and new infections despite implementation of multiple infection prevention interventions. During the second period, an analysis identified a frontline staff member associated with newly colonized infants whose nasal culture grew the clonal MRSA. A marked reduction in colonization followed removal from patient contact. WGS of isolates from years 1-3 showed clonality with maximum SNP differences of 33. Importantly, the year 3 isolates were more closely related to the early year 1 isolates (15-20 SNP differences) than to the late year 1 or year 2 isolates (18-33 SNP differences).


      During a recrudescent MRSA outbreak due to a clonal strain, both contact with a colonized staff member and a putative environmental or personnel reservoir were associated with MRSA acquisition.


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