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Broth Microdilution In Vitro Screening: An Easy and Fast Method to Detect New Antifungal Compounds
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Broth Microdilution In Vitro Screening: An Easy and Fast Method to Detect New Antifungal Compounds

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Comparative Evaluation of Disc Diffusion and E-test with Broth Micro-dilution in Susceptibility testing of

Prashant Gupta1, Vineeta Khare2, Deepak Kumar3

  • 1Assistant Professor, Department of Microbiology, King George's Medical University , Lucknow, U.P, India .

Journal of Clinical and Diagnostic Research : JCDR
|March 5, 2015
PubMed
Abstract

Insights

The disk diffusion method offers a simpler approach for Aspergillus antifungal susceptibility testing, showing good agreement with broth micro-dilution for voriconazole and caspofungin. However, caution is advised when interpreting amphotericin B results with this method.

Area of Science:

  • Medical Mycology
  • Clinical Microbiology
  • Antifungal Resistance

Background:

  • Increasing incidence of invasive Aspergillus infections due to immunosuppression.
  • Limited availability of routine antifungal susceptibility testing for Aspergillus.
  • Need for simpler, cost-effective susceptibility testing methods.

Purpose of the Study:

  • To evaluate the disk diffusion (DD) method for Aspergillus antifungal susceptibility testing (AFS).
  • To compare DD and E-test against the Clinical Laboratory Standard Institute (CLSI) broth micro-dilution (BMD) method.
  • To assess the susceptibility patterns of Aspergillus isolates to amphotericin B, voriconazole, and caspofungin.

Main Methods:

  • Evaluated disk diffusion (DD) for amphotericin B (AMB), voriconazole (VCZ), and caspofungin (CAS).
  • Tested 44 clinical Aspergillus isolates (34 A. fumigatus, 8 A. flavus, 2 A. terreus).
  • Compared DD and E-test on Mueller Hinton Agar (MHA) with CLSI BMD.

Main Results:

  • Disk diffusion showed 87.5% agreement with BMD for AMB; E-test showed 93.8% agreement.
  • Both DD and E-test demonstrated high agreement (93.8% for VCZ, 100% for CAS) with BMD.
  • 31.8% and 9.1% of isolates exceeded epidemiological cut-off values (ECV) for AMB and VCZ, respectively; all were within ECV for CAS.

Conclusions:

  • The CLSI disk diffusion method is a potentially easier, reproducible, and cost-effective AFS method.
  • Interpretation of disk diffusion for amphotericin B requires caution.
  • E-test demonstrates better correlation with BMD compared to disk diffusion.
Keywords:
Amphotericin BAntifungal susceptibilityAspergillusBroth-micro-dilutionCaspofunginDisk diffusionE-testVoriconazole

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