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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
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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

Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases
|April 10, 2008
PubMed

Insights

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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