Methicillin-resistant Staphylococcus aureus clones, Western Australia.

Area of Science:

• Microbiology
• Infectious Diseases
• Public Health

Background:

• Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) emerged in Western Australia in the early 1990s.
• Statewide screening policies have limited epidemic MRSA strains but not specific CA-MRSA clones (SCCmec type IV and V).

Purpose of the Study:

• To characterize the prevalence and genetic features of CA-MRSA clones in Western Australia.
• To assess antimicrobial resistance patterns and the presence of Panton-Valentine leukocidin (PVL) toxin genes in CA-MRSA isolates.

Main Methods:

• Analysis of 4,099 MRSA isolates from July 2003 to December 2004.
• Utilized multilocus sequence and staphylococcal chromosome cassette mec typing for clone characterization.
• Assessed antimicrobial resistance to non-beta-lactam drugs and screened for PVL toxin genes.

Main Results:

• CA-MRSA constituted 77.5% of all analyzed MRSA isolates.
• 22 distinct CA-MRSA clones were identified, with 55.5% exhibiting resistance to multiple non-beta-lactam antimicrobials.
• Five PVL-positive CA-MRSA clones were detected, with some previously PVL-negative clones now testing positive.

Conclusions:

• Multidrug-resistant CA-MRSA clones are emerging and becoming established in Western Australia.
• The increasing prevalence of PVL toxin genes in CA-MRSA is a significant public health concern.
• Continued surveillance and characterization of CA-MRSA are crucial for effective public health strategies.