Related Experiment Videos
Methicillin-resistant Staphyloccocus aureus: evaluation of five selective media
S Davies1, P M Zadik, C M Mason
1Public Health Laboratory, Herries Road, Sheffield S5 7BQ, UK. sdavies@trent.phls.nhs.uk
British Journal of Biomedical Science
|February 24, 2001
Summary
Baird-Parker medium plus ciprofloxacin (BPC) demonstrated the highest sensitivity for isolating methicillin-resistant Staphylococcus aureus (MRSA). Other media showed lower performance, with reduced salt mannitol salt agar plus oxacillin being least effective.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Diagnostic Microbiology
Background:
- Accurate isolation of methicillin-resistant Staphylococcus aureus (MRSA) is critical for infection control.
- Evaluating novel and existing selective media is essential for optimizing MRSA detection.
- Previous recommendations favored specific media formulations for MRSA screening.
Purpose of the Study:
- To compare the diagnostic performance of three selective media (MMSAO, CHRAC, HMO) against established media (OMSAO, BPC) for MRSA isolation.
- To determine the sensitivity and specificity of each medium in detecting MRSA from clinical specimens.
- To identify the most effective medium for direct culture of MRSA.
Main Methods:
- Clinical MRSA screening swabs were inoculated onto five different selective agar media.
- Plates were incubated and examined at 24 and 48 hours for bacterial growth.
- Suspected MRSA colonies were confirmed using biochemical tests (DNase, coagulase, protein A) and methicillin resistance testing.
Main Results:
- Baird-Parker medium plus ciprofloxacin (BPC) exhibited the highest sensitivity (94%) at 48 hours.
- CHROMagar Staph aureus plus ciprofloxacin (CHRAC) showed 70% sensitivity, while mannitol salt agar (7% salt) plus oxacillin (OMSAO) had 61% sensitivity.
- Halifax MRSA medium (HMO) and reduced salt mannitol salt agar plus oxacillin (MMSAO) demonstrated lower sensitivities of 56% and 46%, respectively.
- BPC also resulted in the fewest unnecessary investigations for non-MRSA isolates.
Conclusions:
- Baird-Parker medium plus ciprofloxacin remains the superior choice for direct MRSA culture due to its high sensitivity and specificity.
- CHROMagar Staph aureus plus ciprofloxacin offers reasonable performance, while mannitol salt agar (7% salt) plus oxacillin is moderately effective.
- Halifax MRSA medium is unreliable for MRSA isolation, and reduced salt mannitol salt agar plus oxacillin is the least sensitive option.