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Updated: Jul 2, 2026
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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Comparison of two different sensitivity testing agars for detecting methicillin resistance in Staphylococcus aureus
Qanita Fahim1, Aamer Ikram, Shahid Ahmed Abbasi
1Department of Microbilogy, Armed Forces Institute of Pathology, Rawalpini. qanita_fahim@yahoo.com
Journal of the College of Physicians and Surgeons--Pakistan : JCPSP
|September 2, 2008
Summary
Both Mueller-Hinton and Isosensitest agar show high accuracy for detecting methicillin-resistant Staphylococcus aureus using cefoxitin discs. This study confirms their reliable performance in routine susceptibility testing for MRSA.
Area of Science:
- Clinical Microbiology
- Antimicrobial Susceptibility Testing
- Molecular Diagnostics
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
- Accurate and reliable detection of MRSA is crucial for effective treatment and infection control.
- The mecA gene polymerase chain reaction (PCR) assay is considered the gold standard for MRSA identification.
Purpose of the Study:
- To compare the diagnostic accuracy of Mueller-Hinton agar and Isosensitest agar for detecting MRSA.
- To evaluate the efficacy of cefoxitin disc diffusion testing on these two agar media.
- To determine the optimal zone diameters for cefoxitin disc testing to differentiate MRSA from methicillin-sensitive Staphylococcus aureus (MSSA).
Main Methods:
- A comparative study was conducted on 100 clinical isolates of Staphylococcus aureus (64 MRSA, 36 MSSA) confirmed by mecA PCR.
- Isolates were tested using cefoxitin 30 µg discs on both Mueller-Hinton agar and Isosensitest agar.
- Incubation was performed at 35-37°C overnight in ambient air, following Clinical and Laboratory Standards Institute guidelines.
Main Results:
- Mueller-Hinton agar demonstrated 100% sensitivity and 100% specificity for MRSA detection with a resistance zone diameter (R) ≤ 20 mm.
- Isosensitest agar showed 100% sensitivity and 100% specificity for MRSA detection with a resistance zone diameter (R) ≤ 26 mm.
- Both media achieved high accuracy with cefoxitin disc testing, with minimal overlap between resistant and sensitive isolate zones.
Conclusions:
- Both Mueller-Hinton agar and Isosensitest agar are equally effective for reliable detection of methicillin resistance in Staphylococcus aureus.
- Cefoxitin disc diffusion testing on either medium provides accurate results for routine susceptibility testing.
- The study supports the use of cefoxitin discs on these common agar media for MRSA surveillance and clinical decision-making.
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