Community-acquired, non-multiresistant oxacillin-resistant Staphylococcus aureus (NORSA) in South Western Sydney

Community-acquired oxacillin-resistant Staphylococcus aureus (ORSA) infecti ons are an emerging problem in the 1990s in Sydney, Australia. Laboratory d ata pertaining to all specimens that grew S. aureus between 1/1/1990 and 31 /12/1999 were analysed. A total of 12,909 isolates of S. aureus were obtain ed. The proportions that were non-multiresistant oxacillin-resistant S. aur eus (NORSA) increased from 0.09% in 1990 to 5.5% in 1999. Resistance of NOR SA strains to erythromycin was 8.5%, ciprofloxacin 8.4%, tetracycline 13%, rifampicin 0.7%, and fusidic acid 5.3%. A chart review was performed for ca ses of NORSA infection which occurred 1/1/1998-3/5/1998. Isolates from thes e cases underwent E-test oxacillin MIC testing, mecA determinant PCR, phage typing and pulsed-field gel electrophoresis. All nine of the patients with NORSA were Polynesians, and all had serious soft tissue infections. Bacter aemia was not seen. Only one patient received vancomycin yet all recovered. Isolates from all nine patients contained the mecA determinant. Oxacillin MICs were 1-8 mg/l. Strain differentiation with phage typing and pulsed-fie ld gel electrophoresis showed isolates from eight patients were closely rel ated and were similar to New Zealand WSPP 1 and WSPP 2 strains. Medical pra ctitioners should take specimens for culture and sensitivity from lesions w here infection with S. aureus is likely. Empirical treatment of staphylococ cal infections in Polynesians needs to cover NORSA. Methods to detect oxaci llin resistance need to be robust.