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Community-acquired, non-multiresistant oxacillin-resistant Staphylococcus aureus (NORSA) in South Western Sydney.
I B Gosbell1, J L Mercer, S A Neville
1Department of Microbiology and Infectious Diseases, South Western Area Pathology Service, Liverpool, NSW, Australia. i.gosbell@unsw.edu.au
Pathology
|May 19, 2001
Summary
Community-acquired oxacillin-resistant Staphylococcus aureus (ORSA) infections, specifically nonmultiresistant ORSA (NORSA), increased in Sydney during the 1990s. NORSA infections predominantly affected Polynesian patients with soft tissue infections, and empirical treatment should consider this resistance pattern.
Area of Science:
- Infectious Diseases
- Microbiology
- Epidemiology
Background:
- Community-acquired oxacillin-resistant Staphylococcus aureus (ORSA) emerged as a significant public health concern in Sydney, Australia, during the 1990s.
- The prevalence of nonmultiresistant ORSA (NORSA) demonstrated a notable increase throughout the decade, indicating a growing challenge in clinical settings.
Purpose of the Study:
- To analyze the trends and characteristics of ORSA infections in Sydney from 1990 to 1999.
- To investigate the antibiotic resistance profiles and genetic relatedness of NORSA isolates.
- To identify clinical features and patient demographics associated with NORSA infections.
Main Methods:
- Retrospective analysis of laboratory data for 12,909 Staphylococcus aureus isolates.
- Antimicrobial susceptibility testing for NORSA strains against erythromycin, ciprofloxacin, tetracycline, rifampicin, and fusidic acid.
- Characterization of NORSA isolates from patient infections using E-test oxacillin MIC, mecA PCR, phage typing, and pulsed-field gel electrophoresis.
Main Results:
- The proportion of NORSA among S. aureus isolates rose from 0.09% in 1990 to 5.5% in 1999.
- NORSA strains exhibited varying resistance patterns, with significant rates against tetracycline (13%) and ciprofloxacin (8.4%).
- All nine patients with NORSA infections were of Polynesian descent, presenting with serious soft tissue infections; none developed bacteremia, and all recovered without widespread vancomycin use.
Conclusions:
- The increasing prevalence of NORSA necessitates robust detection methods and consideration in empirical treatment strategies, particularly for Polynesian patients.
- The genetic relatedness of NORSA isolates suggests a common source or clonal spread, similar to strains identified in New Zealand.
- Clinicians should prioritize specimen collection for culture and sensitivity testing in suspected S. aureus infections to guide appropriate therapy.