Antifungal susceptibility of Aspergillus isolates from a Canadian hospital using epidemiological cut-off values

Ref ID: 19203

Author:

S. Jiwa, S. Shokoples, L. Turnbull, B. Jansen, J. Fuller

Author address:

Edmonton, CA

Full conference title:

23rd European Congress of Clinical Microbiology and
Infectious Diseases

Date: 27 April 2014

Abstract:

Objectives: Epidemiologic cut-off values (ECOFFs) have recently been proposed for common Aspergillus species and antifungal agents for the purpose of detecting acquired microbiological resistance. In this study, we examined the antifungal susceptibility profiles of Aspergillus species isolated from respiratory specimens of patients admitted to our hospital for evidence of microbiological resistance.
Methods: Clinical isolates of Aspergillus species recovered from in-patient respiratory specimens between January 2008 and October 2012 were tested against amphotericin B (AMB), itraconazole (ITRA), posaconazole (POSA), voriconazole (VORI) and caspofungin (CASP) by broth microdilution using the CLSI M38-A2 method. Growth endpoints were measured at 24 h of incubation and values >ECOFF were scored as non-wildtype (non-WT).
Results: Of the 423 Aspergillus isolates cultured, A. fumigatus, A. flavus, A. nidulans, A. terreus, A. glaucus, and A. niger comprised 44%, 12%, 10%, 8%, 7%, and 6%, respectively. MIC distribution summaries are shown in Table 1. Three isolates of A. fumigatus had non-WT VORI MICs (2 to 4 mg/L), one of which was non-WT for POSA and ITRA, and five isolates had non-WT CASP MECs of 1 mg/L. A significant number of A. flavus isolates showed non-WT MICs to VORI and POSA, most of which were one doubling dilution >ECOFF; only one of these isolates had a non-WT ITRA MIC. Four A. terreus isolates had non-WT VORI MICs (2 to 4 mg/L) yet posaconazole MICs were <=ECOFF. Conclusions: The clinical correlation of Aspergillus in vitro susceptibility testing is not known and ECOFF values have been proposed to facilitate the detection of microbiological resistance. Although A. fumigatus was most prevalent in this study, several other species were also commonly isolated from respiratory tract specimens. Molecular studies were not used to verify non-WT findings but A. fumigatus showed little evidence of resistance. In contrast, the MIC distributions of the azoles for A. flavus clearly straddle the ECOFF and require further investigation.

Abstract Number: P981

Conference Year: 2013

Link to conference website: http://registration.akm.ch/einsicht.php?XNABSTRACT_ID=167531&XNSPRACHE_ID=2&XNKONGRESS_ID=180&XNMASK

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