Community-associated methicillin-resistant Staphylococcus aureus, Canada

Area of Science:

• Microbiology
• Infectious Diseases
• Epidemiology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen causing skin and soft tissue infections.
• Understanding MRSA strain diversity and epidemiology is crucial for effective treatment and control.

Purpose of the Study:

• To characterize MRSA strains isolated from skin and soft tissue infections in east-central Saskatchewan, Canada.
• To identify the molecular epidemiology and antimicrobial resistance patterns of these MRSA strains.

Main Methods:

• Collection of 184 MRSA strains from patients between 1999 and 2002.
• Molecular subtyping using pulsed-field gel electrophoresis (PFGE).
• Detection of toxin genes (lukF-PV, lukS-PV) and assessment of antimicrobial susceptibility.

Main Results:

• Two major MRSA clusters were identified: Cluster A (CMRSA-2 related) from a long-term care facility and Cluster B (USA400) from community health centers.
• The USA400 strain (Cluster B) harbored lukF-PV and lukS-PV toxin genes and remained susceptible to several antimicrobial classes.
• Over 50% of both clusters exhibited high-level mupirocin resistance.
• This study reports the first detection of the USA400 strain with lukF-PV and lukS-PV toxin genes in Canada.

Conclusions:

• MRSA epidemiology in Saskatchewan is characterized by distinct clusters, including a community-associated strain (USA400) previously identified in the US.
• The presence of specific toxin genes in the Canadian USA400 strain suggests potential for increased virulence.
• High-level mupirocin resistance is prevalent in both identified MRSA clonal groups, impacting topical treatment options.