Detection and expression of methicillin/oxacillin resistance in multidrug-resistant and non-multidrug-resistant Staphylococcus aureus in Central Sydney, Australia.
J Antimicrob Chemother
; 49(5): 793-801, 2002 May.
Article
in En
| MEDLINE
| ID: mdl-12003973
ABSTRACT
Ninety clinical Staphylococcus aureus isolates from separate patients were examined phenotypically and genotypically for susceptibility to methicillin/oxacillin. Thirty were methicillin/oxacillin susceptible and 60 were methicillin and oxacillin resistant (MRSA). The 60 MRSA isolates examined were subdivided into two groups according to their antibiotic profiles and comprised 30 non-multidrug-resistant (NMDR) isolates, resistant to less than two non-beta-lactam antibiotics, and 30 multidrug-resistant (MDR) isolates, resistant to three or more non-beta-lactam antibiotics. Phenotypic and genotypic analysis of methicillin/oxacillin showed that despite use of the guidelines published by the NCCLS for the testing of S. aureus susceptibility to methicillin/oxacillin, MIC values of some NMDR MRSA isolates fell below the NCCLS-recommended breakpoints. Etest strips failed to detect two NMDR MRSA isolates tested with oxacillin and four tested with methicillin. Lowering the NCCLS-recommended oxacillin screen agar concentration from 6 to 2 mg/L and temperature of incubation to 30 degrees C, improved the specificity and sensitivity of NMDR MRSA detection from 87% to 100%. On PFGE analysis these NMDR MRSA strains were genotypically different. Genotypic tests, such as multiplex PCR for the mecA/nuc genes and DNA hybridization for the mecA gene, or phenotypic monoclonal antibody-based tests to detect penicillin-binding protein 2a (PBP2a) offer advantages for problematic isolates in detecting or confirming low-level phenotypic heterogeneous mecA expression of oxacillin and methicillin resistance in NMDR MRSA.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Oxacillin
/
Penicillins
/
Staphylococcus aureus
/
Bacterial Proteins
/
Penicillin Resistance
/
Methicillin Resistance
/
Micrococcal Nuclease
Type of study:
Diagnostic_studies
/
Guideline
Country/Region as subject:
Oceania
Language:
En
Journal:
J Antimicrob Chemother
Year:
2002
Document type:
Article
Affiliation country:
Australia