Methicillin-resistant Staphylococcus aureus in the Australian community: an evolving epidemic

Area of Science:

• Infectious Diseases
• Microbiology
• Epidemiology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health challenge globally.
• Understanding the molecular epidemiology and antimicrobial resistance patterns of MRSA is crucial for effective control strategies.

Purpose of the Study:

• To investigate the antimicrobial resistance and molecular characteristics of MRSA.
• To describe the epidemiology of MRSA in Australian community settings.

Main Methods:

• A nationwide survey of S. aureus isolates from outpatient settings was conducted between July 2004 and February 2005.
• Isolates were characterized using antimicrobial susceptibility testing, coagulase gene typing, pulsed-field gel electrophoresis, multilocus sequence typing, SCCmec typing, and PCR for Panton-Valentine leukocidin (PVL) gene.

Main Results:

• Of 2652 S. aureus isolates, 14.9% were MRSA. Community-associated MRSA (CA-MRSA) prevalence increased from 4.7% in 2000 to 7.3% in 2004.
• The Queensland (QLD) CA-MRSA strain significantly increased in prevalence, while the south-west Pacific (SWP) strain decreased.
• Panton-Valentine leukocidin (PVL) genes were detected in 46% of CA-MRSA strains, notably high in QLD and SWP strains.

Conclusions:

• Community-onset MRSA continues to spread across Australia.
• The hypervirulence determinant PVL is frequently found in common CA-MRSA strains.
• The dynamic changes in MRSA prevalence highlight the necessity for continuous surveillance.