Current molecular epidemiology of methicillin-resistant Staphylococcus aureus in elderly French people: troublesome clones on the horizon

• Main Authors: Claire eRondeau, Guillaume eChevet, Dominique S Blanc, Houssein eGbaguidi-Haore, Marie eDecalonne, Sandra eDos Santos, Roland eQuentin, Nathalie Laure Van Der Mee-Marquet
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2016-01-01
• Series: Frontiers in Microbiology
• Subjects: Staphylococcus aureus; MRSA; elderly patients; carriage; Residents; Bloodstream infection
• Online Access: http://journal.frontiersin.org/Journal/10.3389/fmicb.2016.00031/full

Objective. In 2015, we conducted at 44 healthcare facilities (HCFs) and 21 nursing homes (NHs) a three-month bloodstream infection (BSI) survey, and a one-day prevalence study to determine the rate of carriage of methicillin-resistant Staphylococcus aureus (MRSA) in 891 patients and 470 residents. We investigated the molecular characteristics of the BSI-associated and colonizing MRSA isolates, and assessed cross-transmission using double-locus sequence typing and pulsed-field gel electrophoresis protocol.Results. The incidence of MRSA-BSI was 0.040/1000 patient-days (19 cases). The prevalence of MRSA carriage was 4.2% in patients (n=39) and 8.7% in residents (n=41) (p<0.001). BSI-associated and colonizing isolates were similar: none were PVL-positive; 86.9% belonged to clonal complexes 5 and 8; 93.9% were resistant to fluoroquinolones. The qacA/B gene was carried by 15.8% of the BSI-associated isolates (3/3 BSI cases in intensive care units (ICUs)), and 7.7% of the colonizing isolates in HCFs. Probable resident-to-resident transmission was identified in four NHs.Conclusions. Despite generally reassuring results, we identified two key concerns. First, a worryingly high prevalence of the qacA/B gene in MRSA isolates. Antisepsis measures being crucial to prevent healthcare-associated infections, our findings raise questions about the potential risk associated with chlorhexidine use in qacA/B+ MRSA carriers, particularly in ICUs. Second, NHs are a weak link in MRSA control. MRSA spread was not controlled at several NHs; because of their frequent contact with the community, conditions are favorable for these NHs to serve as reservoirs of USA300 clone for local HCFs.