Background: VORI, the preferred treatment for invasive aspergillosis, is active in vitro against various Asp species as shown by broth microdilution and Etest antifungal susceptibility methods. The semi-solid agar antifungal susceptibility (SAAS) test, based on simulated conditions of in vivo growth, is fast and easy to perform. We compared the agreement of SAAS with the National Committee for Clinical Laboratory Standards (NCCLS) M38-A broth microdilution method and Etest for VORI susceptibility of Asp. Methods: We tested Asp isolates recovered from cancer patients (A. terreus 10; A. fumigatus 10; A. flavus 10). Asp were grown per the NCCLS M38-A document and inocula prepared per each method. RPMI 1640 (NCCLS), 0.5% heart infusion agar (SAAS), and RPMI 1640 agar with 2% glucose (Etest) media were used. Serial 2 fold dilutions were studied for NCCLS (0.03-32 μg/ml) and SAAS (0.25-8 μg/ml) tests. After 48 h growth at 35º C, minimum inhibitory concentrations (MIC) were determined by the concentration at which 100% or >75% growth inhibition occurred for the NCCLS and SAAS tests, respectively. Etest values falling between 2 fold dilutions were adjusted to the next highest concentration for comparison purposes. The overall agreement between methods was determined as the proportion of MICs + 2 dilutions of the corresponding method. Results: All Asp demonstrated susceptibility to VORI. MICs ranged from 1 dilution less than NCCLS. For A. terreus, an Asp species resistant to amphotericin B, the MICs for VORI by all 3 methods were low, with SAAS and Etest results consistently lower than those of NCCLS. Conclusions: MIC testing by 3 independent antifungal susceptibility methods shows that VORI is very effective in vitro against a variety of clinical Asp isolates.
Full conference title:
44th Interscience Conference on Antimicrobial Agents and Chemotherapy
- ICAAC 44th