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Evaluation of mannitol salt agar for detection of oxacillin resistance in Staphylococcus aureus by disk diffusion and
1Institut für Hygiene, Freie Universität Berlin, Germany.
Abstract:
Mannitol salt agar was evaluated for detection of oxacillin resistance in 136 Staphylococcus aureus isolates. All mecA-positive isolates (n = 54) were correctly categorized as oxacillin resistant by the disk diffusion test (1-microgram disk; zone diameter, < 16 mm); the specificity was 97.6%. Agar screening (2 micrograms of oxacillin per ml) revealed a sensitivity of 98.1% and a specificity of 95.1%.
Insights
Mannitol salt agar effectively detects oxacillin resistance in Staphylococcus aureus. This method accurately identifies mecA-positive strains, crucial for guiding antibiotic treatment decisions in clinical settings.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Antimicrobial Resistance
Background:
- Staphylococcus aureus is a significant pathogen.
- Oxacillin resistance in S. aureus is a growing concern.
- Accurate detection of resistance is vital for effective treatment.
Purpose of the Study:
- To evaluate Mannitol Salt Agar for detecting oxacillin resistance in Staphylococcus aureus.
- To compare the performance of disk diffusion and agar screening methods.
Main Methods:
- Tested 136 Staphylococcus aureus isolates.
- Utilized disk diffusion test with 1-microgram oxacillin disks.
- Employed agar screening with 2 micrograms of oxacillin per ml.
Main Results:
- Disk diffusion correctly identified all 54 mecA-positive isolates as oxacillin resistant (97.6% specificity).
- Agar screening demonstrated 98.1% sensitivity and 95.1% specificity.
- Both methods showed high accuracy in detecting oxacillin resistance.
Conclusions:
- Mannitol salt agar is a reliable method for detecting oxacillin resistance in Staphylococcus aureus.
- These findings support the use of Mannitol salt agar in clinical laboratories for routine susceptibility testing.