Epidemiological typing of methicillin resistant Staphylococcus aureus recovered from patients attending a maternity hospital in Ireland 2014–2019

It has previously been reported that maternity hospitals have lower levels of MRSA compared to other healthcare facilities, due to the patient population - mostly healthy patients with limited healthcare contact. In this epidemiological study, all MRSA isolates recovered from patients attending a maternity hospital from 2014 – 2019 were investigated. 171 isolates from adults (n=120) and babies (n=51) from diagnostic and screening investigations were submitted to the National MRSA Reference Laboratory (NMRSARL). Investigations included: spa typing, antimicrobial susceptibility testing, detection of the mecA/mecC genes and lukS-PV and lukF-PV. All were susceptible to glycopeptides, linezolid, rifampicin and mupirocin, while 29 of 171 (17%) were resistant to β-lactam agents only. Thirteen isolates (8%) were resistant to two classes of antibiotic; one resistant to three. All isolates harboured mecA and 33 of 171 (19%) harboured PV-lukF/S. Among the collection, 21 multilocus sequence types (ST) were inferred from 63 spa types. EARS-NET data shows that ST22-MRSA-IV accounts for approximately 75% of MRSA recovered in Irish hospitals. Here, it accounted for only 25.7%. MLST types associated with community acquired MRSA accounted for the remaining 74.3%. These included ST8, ST30, ST1, ST5 and ST88, suggesting a diverse population, harbouring multiple resistance and virulence genes, some of which have been previously associated with outbreaks in Ireland. This study exposes a reservoir of MRSA in the community which may be imported into hospitals, leading to outbreaks. The diversity of MRSA lineages with enhanced virulence factors highlights the need for regular surveillance to ensure appropriate infection prevention and control interventions are implemented promptly.