Background: As for Aspergillus fumigatus, the predominant cause of aspergillosis, Aspergillus terreus
may be responsible for a large spectrum of infections. Those infections may be difficult to manage due
to the intrinsic resistance of A. terreus to amphotericin B. Otherwise, A. terreus has been shown to be
a species complex currently comprising 14 recognized phylogenetic species. The prevalence of those
cryptic species, that may be involved in human disease, is not known. The aim of the present study
was to characterize at the molecular level a panel clinical isolates morphologically identified as A.
Material/methods: We investigated 82 clinical isolates collected in 8 French university hospitals over
a 13-year period (2003-2015). For each isolate, age, sex, underlying disease of the patient, site of
isolation and clinical form of aspergillosis were retrieved. The isolates were initially identified by
standard morphological characteristics. Each isolate was retrospectively identified to the species level
by sequencing the fragments of β-tubulin and calmodulin encoding-genes. Nucleotide sequences were
compared to those of type strains of the different cryptic species of the A. terreus species complex.
Results: The isolates were collected from 50 patients with sex ratio at 1.5 and a mean age of 54 years
mostly from respiratory samples (84%). Underlying diseases were as follow: cystic fibrosis (30%),
chronic broncho-pulmonary disease (14%), haematological malignancy (14%), solid organ transplant
(8%), solid malignancy (6%) and others (28%). Clinical forms encompassed 5 invasive aspergillosis
(IA), 1 case of onychomycosis and 44 cases of bronchial colonisation. A. terreus sensu stricto, found
in 7 of the 8 participating centres, was the most common species (62 isolates, 75.6%) and was
responsible of the 5 cases of IA. Fifty-five isolates were identified as Aspergillus citrinoterreus (18.3%).
Two other cryptic species were identified as Aspergillus hortai (3 isolates, 3.7%) and Aspergillus
alabamensis (2 isolates, 2.4%). Both genes were able to identify the isolates to the species level.
Conclusions: This study shows that 25% of A. terreus clinical isolates may correspond to cryptic
species other than A. terreus sensu stricto. Further studies are warranted to investigate in depth the
clinical impact of those “rare” species. Antifungal susceptibility testing is in progress.
Full conference title:
- ECCMID 27th (2017)