Open AccessAzole Resistance of Aspergillus fumigatus Biofilms Is Partly Associated with Efflux Pump Activity
Author(s) -
Ranjith Rajendran,
Eilidh Mowat,
Elaine McCulloch,
David F. Lappin,
Brian Jones,
Sue Lang,
Jayesh B. Majithiya,
Peter Warn,
Craig Williams,
Gordon Ramage
Publication year - 2011
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.01189-10
Subject(s) - efflux , voriconazole , aspergillus fumigatus , microbiology and biotechnology , azole , in vivo , chemistry , biofilm , mycelium , antibiotics , biology , pharmacology , bacteria , biochemistry , horticulture , antifungal , genetics
This study investigated the phase-dependent expression and activity of efflux pumps inAspergillus fumigatus treated with voriconazole. Fourteen strains were shown to become increasingly resistant in the 12-h (16- to 128-fold) and 24-h (>512-fold) phases compared to 8-h germlings. An Ala-Nap uptake assay demonstrated a significant increase in efflux pump activity in the 12-h and 24-h phases (P < 0.0001). The efflux pump activity of the 8-h germling cells was also significantly induced by voriconazole (P < 0.001) after 24 h of treatment. Inhibition of efflux pump activity with the competitive substrate MC-207,110 reduced the voriconazole MIC values for theA. fumigatus germling cells by 2- to 8-fold. Quantitative expression analysis ofAfuMDR4 mRNA transcripts showed a phase-dependent increase as the mycelial complexity increased, which was coincidental with a strain-dependent increase in azole resistance. Voriconazole also significantly induced this in a time-dependent manner (P < 0.001). Finally, anin vivo mouse biofilm model was used to evaluate efflux pump expression, and it was shown thatAfuMDR4 was constitutively expressed and significantly induced by treatment with voriconazole after 24 h (P < 0.01). Our results demonstrate that efflux pumps are expressed in complexA. fumigatus biofilm populations and that this contributes to azole resistance. Moreover, voriconazole treatment induces efflux pump expression. Collectively, these data may provide evidence for azole treatment failures in clinical cases of aspergillosis.