Fungal infections are increasingly common; including those caused by species of the genus
Aspergillus. The genus Aspergillus is divided in subgenera, and in sections. Within each section there
are numerous cryptic species that can only be differentiated by molecular techniques. The prevalence
and relevance of these cryptic species in the clinical setting are still unknown.
The aim of this study was to analyze the distribution of Aspergillus species among clinical samples
isolates in the Hospital Virgen del Rocío (Spanish tertiary care hospital) collected between January-
Strains: all strains of Aspergillus species isolated from clinical samples, received in the hospital
clinical microbiology laboratory over a period from January to October 2014, were included in the
study. They were isolated from respiratory tract samples (n=119), otic exudates (n=29) and other
Morphological identification: primary culture was performed using Sabouraud, Sabouraudchloramphenicol
and Sabouraud-cycloheximide agars (Oxoid); incubation at 25°C and 30°C, and twice
a week examination for up to 3 weeks. Species identification of the isolates was done according to
macroscopic and microscopic morphology.
Molecular identification: the strains were cultivated for 48 hours on Sabouraud chloramphenicol agar
plates at 30°C and Genomic DNA was extracted with the QIAamp® DNA Mini Kit (Qiagen,
Courtaboeuf, France). Identification of the fungal strains was performed by PCR amplification and
DNA sequencing of the partial beta-tubulin (BT) gene using BT1 and BT4 primers and a BLAST
search analysis (BLASTn) for species identification from the NCBI genomic database
(http://blast.ncbi.nom.nih.gov/) was conducted.
Aspergillus species were cultured from 156 samples belonging to 139 patients.
Attending to their macroscopic and microscopic characteristics, the isolates were identified as: 71 A.
fumigatus, 39 A. flavus, 22 A. niger, 19 A. terreus and 5 Aspergillus spp.
DNA sequencing allowed us to detect cryptic species belonging to six different sections. Aspergillus
section Fumigati included 71 (45.6%) strains of A. fumigatus. Aspergillus section Flavi was
represented by 40 (25.6%) strains: 36 A. flavus, 2 A. tamari, 1 A. minisclerotigenes and 1 A. nomius.
Aspergillus section Terrei included 19 (12.2%) A. terreus strains. Aspergillus section Nigri included 22
(14.1%) strains: 12 A. niger and 10 A. tubingensis. The sections with fewer species were Nidulantes (3
A. nidulans strains) and Versicolores (1 A. sydowii strain).
The five Aspergillus spp. Strains were identified by sequencing as: 3 A. nidulans, 1 A.
minisclerotigenes and 1 A. sydowii.
A. fumigatus has been responsible for almost half of the infections as previously reported.
DNA sequencing allowed us to detect cryptic species belonging to six different sections and to classify
15 (9.6%) isolates of a total of 156 Aspergillus as cryptic species.
Full conference title:
- ECCMID 26th (2016)