A Rare Case Report: Isolation of a Black, Sunflower-Shaped Conidial Fungal Colony from Hair and Skin Scales in a Terrier Dog

Background: Fungal skin infections in companion animals are frequently caused by dermatophytes or common Aspergillus species; however, the isolation of atypical or morphologically distinct fungi remains uncommon. A ۵-year-old terrier dog with scaly skin lesions was examined for possible fungal infection. Methods: Direct microscopic examination of hair and skin scales with KOH preparation was negative for dermatophytes. Nevertheless, culture on Sabouraud dextrose agar (without cycloheximide) at ۲۸ °C yielded rapidly growing, black, fluffy colonies with a powdery surface and a deep black reverse after five days of incubation. Microscopic examination using lactophenol cotton blue staining revealed septate hyphae and conidiophores terminating in a globose vesicle, surrounded by biseriate phialides arranged in a distinctive, radiating, sunflower-like pattern. Results: This morphology differed from Aspergillus niger, in which conidia are typically arranged in dense chains around the vesicle and the colony reverse is usually pale or colorless. Molecular identification using internal transcribed spacer (ITS) sequencing confirmed the isolate as belonging to the A. niger complex (accession number PX۲۴۲۴۴۸), while phylogenetic analysis placed it within a distinct clade related to the black Aspergilli, supporting its unusual phenotype. Conclusion: This case represents a rare isolation of an atypical black Aspergillus strain with unique conidial morphology from a canine dermatological sample. The findings emphasize the need to integrate conventional morphology with molecular and phylogenetic methods for accurate identification of uncommon fungal isolates in veterinary mycology. Recognition of such variants is crucial for improving diagnostic accuracy, understanding epidemiological diversity, and guiding appropriate antifungal management in companion animals.

کلیدواژه ها:

Aspergillus niger complex ، black Aspergilli ، Canine mycosis ، Fungal morphology ، Molecular identification