Aspergillus felis sp. nov., an emerging agent of invasive aspergillosis in humans, cats, and dogs

Abstract

We describe a novel heterothallic species in Aspergillus section Fumigati, namely A. felis (neosartorya-morph) isolated from three host species with invasive aspergillosis including a human patient with chronic invasive pulmonary aspergillosis, domestic cats with invasive fungal rhinosinusitis and a dog with disseminated invasive aspergillosis. Disease in all host species was often refractory to aggressive antifungal therapeutic regimens. Four other human isolates previously reported as A. viridinutans were identified as A. felis on comparative sequence analysis of the partial β-tubulin and/or calmodulin genes. A. felis is a heterothallic mold with a fully functioning reproductive cycle, as confirmed by mating-type analysis, induction of teleomorphs within 7 to 10 days in vitro and ascospore germination. Phenotypic analyses show that A. felis can be distinguished from the related species A. viridinutans by its ability to grow at 45°C and from A. fumigatus by its inability to grow at 50°C. Itraconazole and voriconazole cross-resistance was common in vitro.

Figure 1. Tissue invasion by fungal hyphae in a cat with SOA.

Hematoxin & Eosin- (A) and Grocott- (B) stained section of nasal mucosa and turbinates demonstrating granulomatous rhinitis (A) and submucosal invasion by septate branching fungal hyphae (B).

Figure 2. Partial calmodulin gene (calM) maximum parsimony (MP) tree.

Phylogenetic analysis for A. felis sp. nov isolates and closely related species as conducted in MEGA5 showing best scoring MP tree constructed using the close-neighbor-interchange algorithm . Bootstrap percentages of the MP analysis are presented at the nodes for values >70%. Trees are drawn to scale, with branch lengths calculated using the average pathway method, expressed in units of the number of changes over the whole sequence. Isolates from clinical specimens used in this study are in bold. Isolate DTO 176-F1 was from an indoor air sample in Germany.

Figure 3. Partial β-tubulin gene (benA) maximum parsimony (MP) tree.

Phylogenetic analysis for A. felis sp. nov isolates and closely related species as conducted in MEGA5 showing best scoring MP tree constructed using the close-neighbor-interchange algorithm . Bootstrap percentages of the MP analysis are presented at the nodes for values >70%. Trees are drawn to scale, with branch lengths calculated using the average pathway method, expressed in units of the number of changes over the whole sequence. Isolates from clinical specimens used in this study are in bold.

Figure 4. Aspergillus felis.

Colonies growing 7 days at 25°C on CYA (A) and MEA (B); Crossing of CBS 130245 and 130246 at 30°C (C); Conidiophores and conidia (D, E and G); Cleistothecium (F); Ascospores (H-I).

Figure 5. Radial growth determination at temperatures ranging from 9°C to 50°C.

Type strains of A. viridinutans (CBS 127.56) and A. fumigatus (CBS 133.61) and 4 isolates of A. felis (CBS 130245, CBS 130246, CBS 130247, CBS 130248).

Figure 6. Cat with sino-orbital aspergillosis (invasive fungal rhinosinusitis) caused by A. felis with exophthalmia and prolapse of the nictitating membrane (third eyelid) associated with a retrobulbar fungal granuloma (A).

Coronal CT scan soft-tissue post-contrast view showing retrobulbar fungal granuloma occupying the inferior aspect of the orbit with involvement of the adjacent paranasal subcutaneous tissues (B).