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Influence of disk preparation on detection of metallo-beta-lactamase-producing isolates by the combined disk assay

Soraya S Andrade1, Renata C Picão, Eloiza H Campana

  • 1Laboratório Especial de Microbiologia Clínica, Universidade Federal de São Paulo, São Paulo, Brazil. soraya.andrade@lemc.com.br

Journal of Clinical Microbiology
|April 6, 2007
PubMed

Insights

The combined disk assay for detecting metallo-beta-lactamase (MBL) producers can yield inconsistent results. Only the imipenem/EDTA combination consistently produced reliable inhibition zones across different preparation methods.

Area of Science:

  • Microbiology
  • Clinical Diagnostics
  • Antimicrobial Resistance

Background:

  • Metallo-beta-lactamase (MBL) producing bacteria are a significant public health concern.
  • The combined disk assay is a common method for detecting MBL-producing isolates.
  • Variability in disk preparation can affect the accuracy of diagnostic tests.

Purpose of the Study:

  • To evaluate the reliability of different beta-lactam/metallo-beta-lactamase inhibitor (IMBL) combinations in the combined disk assay.
  • To identify a consistent and accurate method for detecting MBL-producing bacteria.

Main Methods:

  • Testing of 10 different beta-lactam/IMBL combinations using the combined disk assay.
  • Assessment of inhibition zone sizes produced by each combination.
  • Comparison of results based on variations in disk preparation methods.

Main Results:

  • Significant variability in inhibition zone sizes was observed for most beta-lactam/IMBL combinations.
  • The preparation method of the combined disks influenced the test results.
  • Only the imipenem/EDTA combination demonstrated consistent results regardless of preparation method.

Conclusions:

  • The imipenem/EDTA combination offers a reliable option for the combined disk assay in detecting MBL producers.
  • Standardization of disk preparation is crucial for other beta-lactam/IMBL combinations to ensure accurate MBL detection.

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