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Updated: Jul 6, 2026
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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Comparison of phenotypic methods for penicillinase detection in Staphylococcus aureus
M Kaase1, S Lenga, S Friedrich
1Department of Medical Microbiology, Ruhr-University Bochum, Bochum, Germany. martin.kaase@rub.de
Summary
Penicillinase testing in Staphylococcus aureus requires accurate methods. While cloverleaf and zone-edge assays show promise for detecting penicillin resistance, blaZ PCR remains the most sensitive method.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Molecular Biology
Background:
- Penicillinase production is a key mechanism of penicillin resistance in Staphylococcus aureus.
- Accurate detection of penicillinase is crucial for guiding antibiotic therapy, especially for isolates with low penicillin Minimum Inhibitory Concentrations (MICs).
Purpose of the Study:
- To compare the diagnostic performance of five phenotypic penicillinase detection assays against a molecular benchmark (blaZ PCR).
- To evaluate the clinical utility of different phenotypic methods for identifying penicillinase-producing Staphylococcus aureus.
Main Methods:
- A total of 197 Staphylococcus aureus isolates were tested.
- Five phenotypic assays were evaluated: starch-iodine plate, nitrocefin test, cloverleaf assay, and penicillin zone-edge determination.
- Results were compared against a gold standard polymerase chain reaction (PCR) assay for the blaZ gene.
Main Results:
- The starch-iodine plate and nitrocefin tests exhibited low sensitivities (42.9% and 35.7%, respectively).
- The cloverleaf assay (67.8% sensitivity) and penicillin zone-edge determination (71.4% sensitivity) demonstrated moderate performance.
- All tested phenotypic methods were less sensitive than the blaZ PCR assay.
Conclusions:
- Phenotypic assays like the cloverleaf and zone-edge methods may be suitable for penicillinase testing in certain clinical settings.
- However, blaZ PCR offers superior sensitivity for detecting penicillinase-producing Staphylococcus aureus.
- Further optimization or alternative phenotypic strategies may be needed for improved diagnostic accuracy.
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