Molecular epidemiology of meticillin-susceptible Staphylococcus aureus in the neonatal intensive care unit

Staphylococcus aureus – both meticillin-resistant S. aureus (MRSA) and meticillin-susceptible S. aureus (MSSA) – is a major cause of neonatal infections. Infection control measures have not lowered the incidence of MSSA infections to the same degree as that of MRSA infections. To investigate the transmission pathway of MSSA in neonatal intensive care unit (NICU) using genetic analysis. Neonatal patients, their parents, and healthcare workers were swab-tested in the NICU at our hospital at the time of hospitalization and then every month thereafter from October 1st, 2018 to March 31st, 2019. Whole-genome sequencing was performed to test for MSSA strains. Multi-locus sequence typing and single nucleotide polymorphism analysis were used to identify strains and understand their relatedness. There were 16 MSSA-positive patients. Four MSSA-positive patients shared strains from the same phylogenetic groups as those of healthcare workers. One presented the same strain as the parent. MSSA-positive twin neonates shared the same strain. Ten had sporadic strains; 32 of the 97 tested healthcare workers were MSSA positive. The findings of this study suggest that the route of transmission of MSSA in NICU may be through MSSA in the hospital environment in addition to horizontal transmission via healthcare workers. Along with hand hygiene with alcohol, thorough environmental maintenance and parental education are important for infection control in NICUs targeting MSSA.