What came first the staff or the patient? – Genomic sequencing reveals silent carriage and potential transmission of MRSA between staff and patients within a NICU

Reviewed by LaToya A. Forrester MPH, CIC, Infection Control Consultant, National Institutes of Health Clinical Center

Whole genome sequencing (WGS) could be used to identify healthcare associated outbreaks sooner, leading to timely deployment of mitigation strategies to cease further transmission. After 4 infants in a NICU were identified with invasive MRSA infections, WGS was performed on 23 MRSA isolates from 18 infants and 5 healthcare personnel (HCP) and identified 2 distinct phylogenetic clades. Clade 1 was comprised of 10 infants and 1 HCP (HCP 11) and clade 2 identified 3 infants and 1 HCP. Within clade 1, 8 infants were cared for by HCP 11 who also cared for an infant who 7 months prior had the same highly virulent strain of MRSA; clade 2 was associated with asymptomatic carriage. Directionality of MRSA transmission cannot be ascertained, however genetic sequencing coupled with additional epidemiological findings strengthens the assertion that HCPs with prolonged colonization and shedding could lead to transmission of MRSA to infants.

Madera S, McNeil N, Serpa PH, et al. Prolonged silent carriage, genomic virulence potential and transmission between staff and patients characterize a neonatal intensive care unit (NICU) outbreak of methicillin-resistant Staphylococcus aureus (MRSA). Infect Control Hosp Epidemiol. 2023;44(1):40-46. doi:10.1017/ice.2022.48

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