Current Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Elderly French People: Troublesome Clones on the Horizon.

Claire Rondeau,Marie Decalonne,Guillaume Chevet,Nathalie Van Der Mee-Marquet,Dominique S Blanc,Roland Quentin,Sandra Dos Santos,Houssein Gbaguidi-Haore

doi:10.3389/fmicb.2016.00031

Abstract

Objective: In 2015, we conducted at 44 healthcare facilities (HCFs) and 21 nursing homes (NHs) a 3-month bloodstream infection (BSI) survey, and a 1-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.Conclusion: 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.

Highlights

Methicillin-resistant Staphylococcus aureus (MRSA) infections have long been associated with healthcare facilities (HCFs) and remain a matter of concern, due to the morbidity and mortality associated with the infections they cause
Epidemiology Nineteen cases of bloodstream infections (BSI) due to MRSA were identified, 12 in male patients and seven in female patients hospitalized in short-stay units, including three in intensive care units (ICUs)
All but one of the MRSA isolates were resistant to fluoroquinolones (94.7%) (Supplementary Table S1); 12 were resistant only to methicillin and fluoroquinolones (63.2%)

Summary

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) infections have long been associated with healthcare facilities (HCFs) and remain a matter of concern, due to the morbidity and mortality associated with the infections they cause (de Kraker et al, 2011). Over the last 20 years, the adherence of healthcare workers to infection control guidelines for patients with MRSA carriage has improved. This approach has proved effective, leading to a marked decrease in the incidence of healthcare-associated infections (HAIs) due to MRSA (Cooper et al, 2004; McGinigle et al, 2008; Rolain et al, 2015). The spread of the ST8-USA300 clone is a matter of particular concern. These MRSA isolates are increasingly being implicated in HAIs (Tenover and Goering, 2009). Two clusters of ST8-USA300 infections were recently described, one in a rehabilitation care center (Fournier, 2013) and the other in a residential home (Haut Conseil de la Santé Publique, 2014)

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