Molecular identification and antifungal susceptibility of cryptic Aspergillus section Fumigati isolated in a multicenter study in Spain (Madrid Aspergillus Resistance Study)

Teresa Pelaez Garcia


Background: Invasive aspergillosis (IA) is an emerging disease whose incidence continues
increasing. IA is mainly caused by Aspergillus fumigatus, however, some cases of IA are
caused by cryptic species from Aspergillus section Fumigati. Their frequency in the clinical
setting is between 10 and 15%, but studies about their antifungal susceptibility are scarce.
The aim of this study was to analyze the antifungal susceptibility of 80 clinical and
environmental strains of Aspergillus section Fumigati in a Madrid multicenter study (Madrid
Aspergillus Resistance, MAR study).
Material/methods: From a total of 1,489 isolates (984 clinical, 505 environmental), 80 strains
of cryptic Aspergillus section Fumigati were isolated in the multicenter study. Sixty four
(6.5%) were clinical isolates and sixteen (3.2%) were environmental. Species identification
was developed using molecular identification sequencing β-tubulin and rodlet A genes.
Antifungal susceptibility using broth microdilution method was tested for all the strains
according to the guidelines of CLSI (Clinical and Laboratory Standards Institute). The
antifungals analyzed were amphotericin B (AMB), itraconazole (ITZ), voriconazole (VCZ),
posaconazole (POS), terbinafine (TB), anidulafungin (AN), caspofungin (CA), and micafungin
(MC). A. fumigatus ATCC 2004305 and A. flavus ATCC 2004304 were used as control
strains. With regard to antifungal susceptibility drugs, due to the lack of defined cutoff values
for these antifungal agents against these species, the antifungal susceptibility of A. fumigatus
was used as the reference epidemiological cutoff values. A. fumigatus ATCC 2004305 and
A. flavus ATCC 2004304 were used as control strains.
Results: Six different species were identified: A. lentulus (n=40), N. udagawae (n=18), A.
novofumigatus (n=9), A. fumigatiaffinis (n=5), N. hiratsukae (n=5), and A. viridinutans (n=3).
Antifungal susceptibility testing showed heterogeneous patterns among these six species.
Most A. lentulus and A. fumigatiaffinis isolates showed the highest MICs to AMB (2.07 and
2.30, geometric mean (GM), respectively). In addition, A. lentulus presented a resistant
profile against azoles, showing ITZ and VCZ MICs >1 μg/ml, however, it was susceptible to
echinocandins and TB. A. viridinutans and A. novofumigatus showed high resistance to all
azoles tested with the following geometric means for ITZ, VZ and POS: 5.04/4.32, 4/3.43
and 0.63/0.86. Moreover, A. novofumigatus showed the highest MICs against TB (GM 0.68)
as well as A. fumigatiaffinis (GM 0.66). Finally, N. udagawae showed high resistance to AMB
(GM 1.78) and VCZ (GM 1.42). N. hiratsukae was susceptible to all antifungals tested.
Conclusions: In our knowledge, this is the largest cryptic Aspergillus Section Fumigati
collection tested. Cryptic species showing decreased susceptibility to azoles are recovered
from clinical samples and the hospital environment. Resistance to VZ is particularly
worrisome, as it is the current pillar of IA treatment. The emergent role of Aspergillus
fumigatus cryptic species warrants further resistance monitoring. This study was partially
supported by FIS (PI13/02783).


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Full conference title: 

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