Molecular characterization and azole susceptibility of Aspergillus flavus species complex clinical isolates

Françoise Botterel Chartier


Background: Section Flavi is  one of the most significant sections  in the genus Aspergillus, and species of this section can cause invasive aspergillosis as well as allergic diseases  in humans.  The high number  of  species  belonging to the Flavi section,  and  their morphological similarity make their precise identification difficult by phenotypic methods. In  this  study, we present data  on molecular characterization and antifungal susceptibility profile of French clinical isolates of Flavi section.

Material/methods: Eighty fungal isolates, reported as A. flavus,  were included in the study.  These clinical isolates  were  recovered from several specimens  over a  15-year period  (2001-2015). Theisolates were initially identified  by morphological characteristics.  After  subculture, each isolate wasidentified to the species level by sequencing a locus/region of the β-tubulin and calmodulin genes.The isolates were also screened for their susceptibilities to azoles antifungal agents on 3-sectors agar plates containing itraconazole, voriconazole  and  a   drug-free  control. Azole resistance was confirmedby evaluating the MIC using Etest® on RPMI 1640.

Results: Among the 80 isolates, molecular analysis of the partialβ-tubulinand calmodulin sequencesshowed that 78 isolates were A. flavus sensustricto and 2  isolates were identified  as A. parasiticusand A. tamarii, respectively. These 2   strains were isolated from sputa and were not resistant to azole antifungal drugs. Among the A. flavussensu strictoisolates, a   limited polymorphism was observed for the partial β-tubulingene: for 75 isolates (96%), sequences were identical to the reference sequence. For partial calmodulin gene, a   higher degree of polymorphism was observed with sequences identical to the references sequences found in only 14 isolates  (18%).  Moreover, 2   strains of A. flavus  sensustricto were resistant to voriconazole but not to itraconazole. Analysis of CYP51Agene polymorphism for these isolates is in progress.

Conclusions: For the first  time in  France, we molecularly characterized  a   large collection of clinical isolates belonging to A. flavussection. Most of  the isolates were  identified as A. flavussensu strictoand were susceptible  to azole antifungal  drugs. Nevertheless,  the occurrence of a    few  resistant isolates highlights the importance of antifungal susceptibility testing.


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European Congress of Clinical Microbiology and Infectious Diseases
    • ECCMID 26th (2016)