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Molecular identification and antifungal susceptibility of clinical Aspergillus terreus complex isolates

Abstract number: P2102

Escribano P., Peláez T., Recio S., Buendía B., Bouza E., Guinea J.

Background: Although Aspergillus fumigatus is still the most frequent species causing invasive aspergillosis (IA), other species of Aspergillus are emerging. Molecular techniques are necessary to identify clinical Aspergillus spp. isolates to species level and to provide a better understanding of the epidemiology of IA. We identified a collection of recent clinical Aspergillus terreus complex isolates using molecular techniques. We also obtained their antifungal susceptibility to triazoles and amphotericin B (AMB).

Methods: We studied 89 clinical A. terreus complex (morphological identification) isolates collected from October 2005 to March 2010. Isolates were from 72 patients, 12 of whom had proven (n = 3) or probable IA, according to EORTC criteria. Only 1 isolate per sample was selected and subsequently identified by amplification and sequencing of the b-tubulin, and calmodulin genes. A BLAST search was performed to identify the isolates. To avoid the presence of cryptic species initially identified as A. terreus, a phylogenetic tree was obtained using the two regions sequenced, including the reference sequences. Antifungal susceptibility to itraconazole (ITRA), voriconazole (VORI), posaconazole (POSA), and AMB was determined using the CLSI M38-A procedure. The antifungal activity of AMB was also obtained using the Etest.

Results: Molecular identification proved that all isolates were A. terreus sensu stricto. The antifungal susceptibility of the isolates (range of MICs, MIC90, and geometric mean), in mg/ml, was as follows: ITRA (0.25–2/2/1.097), VORI (0.125–2/2/1.176), POSA (0.25–1/1/0.836), AMB CLSI (4–32/16/9.689), and AMB Etest (0.75–64/6/3.106). None of the isolates showed an MIC for ITRA, VORI, or POSA greater than 2 mg/ml. In contrast, the MICs for AMB were significantly higher than those found for the 3 triazoles (P < 0.001), regardless of the method chosen.

Conclusions: No cryptic species of the A. terreus complex causing IA or colonization were found in the isolates studied. A. terreus sensu stricto, a species with a known lack of susceptibility to AMB, remains fully susceptible to the triazoles.

Session Details

Date: 07/05/2011
Time: 00:00-00:00
Session name: Abstracts of 21st ECCMID / 27th ICC
Subject:
Location: Milan, Italy, 7 - 10 May 2011
Presentation type:
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