Summary of surveillance of methicillin-resistant Staphylococcus aureus strains isolated from bacteremia in the province of Quebec, 2019-2020

The Committee for the Surveillance of Nosocomial Infections (SPIN), in collaboration with the Committee on Nosocomial Infections of Quebec (CINQ), has established a mandatory bacteremia surveillance program staphylococci (S) aureus in 2006. Analysis of the results of this surveillance indicated that a significant proportion of bacteremia S. aureus Resistance to methicillin (MRSA) was not a nosocomial acquisition (Galarneau et al. 2008). Therefore, the CINQ considered it important to examine the molecular profile of MRSA strains isolated from blood cultures in Quebec, regardless of the category of attribution, nosocomial or community, of the bacteremia.

The Department of Health and Human Services has commissioned the Laboratoire de santé publique du Québec (LSPQ) to study the molecular profile of MRSA strains 2019-2020 for a fifth one-year period. This summary presents the results of the laboratory analysis of this surveillance. The characterization of the strains includes their antibiogram, determination of the epidemic type (MRSA-AH [acquisition hospitalière] against MRSA AC [acquisition communautaire]) by gene sequencing spa and detection of the Panton Valentine leukocidin (PVL) toxin gene by the nucleic acid amplification technique (NAAT).

The 2019-2020 surveillance of MRSA strains isolated from bacteremia made it possible to track MRSA trends in Quebec for the fifth time in the past 10 years. It confirms the dramatic reduction in HA-MRSA, reflecting the effectiveness of the interventional tools used since 2005 in all Quebec hospital sites to combat nosocomial infections. It should also be noted that high sensitivity rates were maintained for the major antibiotics of clinical interest.

On the other hand, the 2019-2020 surveillance describes a spectacular increase (> 145%) in the proportion of CA-MRSA strains, which represented 46.5% of the strains isolated in Quebec. It also confirms an increase in CA-MRSA strains that do not express the PVL toxin gene. A better understanding of the risk factors associated with the occurrence of community-acquired MRSA could contribute to the implementation of targeted prevention strategies, such as those implemented for the prevention and control of healthcare-associated infections in Quebec.

For each submitted strain, the hospital laboratories received an analysis report that included the results of typing, antibiotic susceptibility, and the presence of the PVL toxin. Due to the COVID-19 pandemic, the report including analyzes of epidemiological data related to the surveillance of these MRSA strains has not been finalized.

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