Patterns of Triazole Cross-Resistance/Susceptibility among a Large Collection of Clinical Isolates of Aspergillus.

D. J. DIEKEMA, S. MESSER, R. HOLLIS, L. BOYKEN, S. TENDOLKAR, J. KROEGER, M. A. PFALLER;

Author address: 

Univ. of Iowa Coll. of Med., Iowa City, IA.

Abstract: 

Background: Several mechanisms of triazole-resistance in A. fumigatus have been described (e.g. cyp51A mutations, efflux pumps). Specific mutations are predicted to result in different patterns of cross-resistance among itraconazole (ITR), voriconazole (VOR), posaconazole (POS) and ravuconazole (RAV). Few data exist to describe MIC correlations among large collections of clinical Aspergillus, including species other than A. fumigatus. Methods: We examined 771 Aspergillus clinical isolates collected from 2000-2006 as part of global antifungal surveillance (553 A. fumigatus, 76 A. flavus, 59 A. niger, 35 A. terreus, 24 A. versicolor, and 24 other Aspergillus spp). Susceptibility testing was performed by CLSI M38A broth dilution against ITR, VOR, POS and RAV. We examined the potential for cross-resistance using measures of correlation overall and by species. Results: Most Aspergillus had MICs of 1 μg/mL (see Table). For A. fumigatus, the strongest correlations were seen for VOR-RAV (r=0.7) and ITR-POS (r=0.4). Similarly, for A. flavus only VOR-RAV and ITR-POS MICs demonstrated significant positive correlations RAV, VOR and POS activity against Aspergillus according to ITR MIC Conclusions: We demonstrate a correlation among triazole MICs for Aspergillus, which for the most common species (A. fumigatus and A. flavus) is strongest between VOR-RAV and ITR-POS. However, Aspergillus with MICs of >2 μg/mL to VOR or POS remain extremely rare (
2007

abstract No: 

M-523

Full conference title: 

47th Interscience Conference on Antimicrobial agents and Chemotherapy
    • ICAAC 47th