A new automated antifungal susceptibility test for Aspergillus fumigatus

Ref ID: 19225

Author:

J. Barbosa, S. Farinha, I. Ramos, H. Gonçalves, A.G. Rodrigues, C. Pina-Vaz

Author address:

Porto, PT

Full conference title:

23rd European Congress of Clinical Microbiology and
Infectious Diseases

Date: 27 April 2014

Abstract:

Objectives: Aspergillus fumigatus can cause invasive aspergillosis, a potentially life-threatening infection with a mortality rate of approximately 50% despite adequate treatment. Antifungal susceptibility tests are not routinely performed since they are cumbersome. Our team previously demonstrated that BACTEC blood culture system could rapidly detect Aspergillus sp growth. The objective of this study was to develop an antifungal susceptibility test for A. fumigatus using BACTEC Mycosis IC/F culture vials.
Methods: Fifty clinical isolates, an ATCC 46645 type strain (all considered susceptible to antifungal) and five additional strains of A. fumigatus, with high MIC values to azoles, were studied. 104 to 105 conidia/mL (DO 0.5) were inoculated in BACTEC Mycosis IC/F vials; one vial without antifungal (positive control) and the others with different antifungals at its respective breakpoint concentration, according to Espinel-Ingroff (2010): amphotericin B (AMB), caspofungine (CASPO), posaconazole (POSA) and voriconazole (VORI); fluconazole (FLU) was used as a control, since A. fumigatus is resistant. The time needed for each vial to become positive was registered – Tp; ratio between antifungalTp and positive controlTp was calculated. Statistical analysis was performed with SPSS 20.0.
Results: For all the experiments, controlTp ranged between 10h30-12h20; for the susceptible strains, antifungalTp corresponded to 60h40-215h for AMB, 34H50-120h for POSA and 64h80-210h for VORI. Strains showing higher MIC values, as well as in vials containing FLU or CASPO, Tp was similar to controlTp. Ratio between antifungalTp and controlTp for susceptible strains was more than 6 times for AMB and VORI and more than to 3 times for POSA.
Conclusion: The BACTEC system provides an accurate, fast, simple and automated method for assessment of BACTEC A. fumigatus susceptibility to VORI, POSA and AMB, with excellent correlation with classic microdilution method but not for CASPO. The work presented here is the subject of an international patent-pending application (PCT/IB2012/052807) on behalf of the authors.

Abstract Number: P1539

Conference Year: 2013

Link to conference website: http://registration.akm.ch/einsicht.php?XNABSTRACT_ID=166460&XNSPRACHE_ID=2&XNKONGRESS_ID=180&XNMASK

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