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

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.

Panton–Valentine leukocidin-positive Staphylococcus aureus : a position statement from the International Society of Chemotherapy

“…Nonetheless, the clinical significance of qacA/B carriage itself remains unclear. While many studies report minimal qacA/B carriage in MRSA over sustained periods of time in intensive care settings, others continue to report high qacA/B carriage and reduced susceptibility to chlorhexidine in S. aureus and CoNS [91,92]. Recently, qacA/B carriage has also been reported in PVL+ve MSSA from osteomyelitis and necrotising pneumonia [92].…”

Time for biocide stewardship?

“…The prevalence of qacA/B in S. aureus reported over the last decade is very variable although the drivers for high carriage are not clear. While some studies continue to report declining susceptibility to chlorhexidine and increasing prevalence of qacA/B in MRSA from a range of clinical settings 8,9 , other studies, including our own work, report low presence of qacA/B in S. aureus from screening samples and bacteraemia patients 10,11 . However, we have shown a high prevalence (80%) of qacA/B in S. epidermidis isolates from blood cultures randomly collected over 6 years in an intensive care unit in Scotland, with qacA/B carriage coinciding with reduced susceptibility to chlorhexidine 11 .…”

Transmission and Long-Term Colonization Patterns of Staphylococcus aureus in a Nursing Home

“…The host deprived of the protective role of commensal microorganisms is more vulnerable for colonization with potentially pathogenic bacteria. Rondeau et al (2016) found that the antibiotic therapy and health status of the nursing home residents were significantly associated with MRSA colonization [14]. The adverse effects of the use of antibiotics are also well-known for their contribution to the development of the acquired antibiotic resistance among microorganisms [15].…”