The Problem: Novel community-acquired, non-multiresistant strains of oxacillin- (methicillin-) resistant Staphylococcus aureus (ORSA) have emerged in many parts of the globe. Little is known of the clinical features, the epidemiology, and the antibiotic treatment of these strains. Materials and Methods: A retrospective chart review was performed on patients presenting to Emergency Departments or Dermatology Clinics with staphylococcal infections. Patients were stratified into three groups, non-multiresistant ORSA (NORSA), multiresistant ORSA (MORSA) and oxacillin-susceptible S. aureus, and clinical comparisons made. Strains of NORSA and MORSA were typed using antibiograms, phage typing and pulsed-field gel electrophoresis. Antimicrobial studies were performed to compare different methods of detecting resistance to oxacillin and to non-beta-lactams. Time-kill studies were performed with one drug to explore killing kinetics. The interaction between drug combinations was examined using disk approximation and time-kill methodologies. A single point pharmacodynamic analysis was performed. Results: There was an increase in infections with NORSA, MORSA and OSSA. NORSA strains appeared to be more virulent than OSSA and MORSA strains. NORSA was strongly associated with skin and soft tissue infections and with Polynesians. Most of the NORSA strains were related to New Zealand ????Western Samoan Phage Pattern???? (WSPP) isolates, and unrelated to community-acquired, non-multiresistant MRSA strains from Western Australia. Two patients were found to have British EMRSA-15 strains. NORSA strains were unrelated to MORSA strains. Resistance to rifampicin, fusidic acid, ciprofloxacin and trimethoprim emerged in the time-kill assays. Combinations of antibiotics, particularly with ciprofloxacin, often showed antagonism. Gentamicin, fusidic acid, clindamycin, teicoplanin, vancomycin, and linezolid were predicted to perform well. Ciprofloxacin, erythromycin, doxycycline, flucloxacillin and quinupristin/dalfopristin were predicted to fail. Conclusions: WSPP strains of New Zealand and EMRSA-15 strains from Britain exist in South Western Sydney. These organisms are virulent, and increasing in incidence in several areas of Australia. Antimicrobial treatment of infections with these strains is problematic and requires further study.
| Identifer | oai:union.ndltd.org:ADTP/212677 |
| Date | January 2003 |
| Creators | Gosbell, Iain Bruce, South Western Sydney Clinical School, UNSW |
| Publisher | Awarded by:University of New South Wales. South Western Sydney Clinical School |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Iain Bruce Gosbell, http://unsworks.unsw.edu.au/copyright |
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