Abstract:

Objective To investigate the mechanism of azole resistance in Aspergillus fumigatus. Methods An isolate of Aspergillus fumigatus was collected from bronchoalveolar lavage fluid（BALF） of a patient with invasive aspergillosis（IA）. By microbroth dilution,the minimal inhibitory concentrations（MIC）/minimal effective concentration（MEC） of itraconazole,voriconazole,posaconazole and amphotericin B and caspofungin were determined according to the Clinical and Laboratory Standards Institute（CLSI） M38-A2. The full-length region of the gene encoding the target enzyme of azoles（cyp51A gene including its promoter） was cloned and sequenced. Microsatellite genotyping was performed by amplifying and determining the isolate's 9 microsatellite loci,and the genetic relationships among isolates with the same genotype were then established by cluster analysis using unweighted pair-group method with arithmetic means（UPGMA）. Results For this isolate,the MIC of itraconazole,voriconazole,posaconazole and amphotericin B were >16,2,0.5 and 2 μg/mL. The MEC of caspofungin was 0.25 μg/mL. The sequence analysis of cyp51A gene showed the presence of 2 copies （-288--322）of a 34 bp sequence in tandem in the promoter of cyp51A gene together with the presence of 3 point mutations at T364A,T960A and T1554A,which were accordingly deduced amino acid substitution including TR34/L98H/S297T/F495I. Microsatellite genotyping indicated that this isolate had a unique genotype being different to those reported previously in Europe and Asia. Conclusions The azole-resistant isolate of Aspergillus fumigatus from BALF harboring amino acid substitution TR34/L98H/S297T/F495I has been isolated with a unique genotype being different to isolates reported before.

Key words: Azoles, Drug resistance, Aspergillus fumigatus, cyp51A