A new case of mycotic disease due to Phialosimplex caninus sp.nov. (Sigler et al. 2010 ) in a dog

Recently, Sigler and co-workers (2010) investigated the identity of six isolates (five from dogs and one from a human source) that resembled Sagenomella species based on morphological analysis. Phylogenetic analyses of internal transcribed spacer (ITS) and small subunit (SSU) region sequences revealed that all of the canine-associated isolates were distinct from Sagenomella species. The new anamorphic genus and species Phialosimplex caninus was described to accommodate the clinical isolates (Sigler at al. 2010, Med Mycol 48: 335–345). This report describes a new case of deep infection in a dog caused by P. caninus showing highly pleomorphic forms in affected tissues. A 3 year old, female, crossbreed dog was presented to visit for anorexia and depression. The clinical examination revealed generalized lymphadenomegaly and mild hyperthermia. Fine needle aspiration cytology (FNAC) from enlarged lymph nodes revealed marked fungal macrophagic lymphadenitis. The fungal elements, variable in shape and dimensions, included monocellular yeast-like elements, cigar-shaped and big forms with a thick wall resembling chlamydospores, and septate, branched hyphae showing single phialides sometimes bearing conidia in chains. Culture on Sabouraud Dextrose Agar (SDA) at 25° C yielded grey-yellowish, fast growing colonies. At microscopy, septate, branched narrow hyphae were present. Conidiogenous cells were simple phialides borne laterally on the vegetative hyphae or occasionally on short, unbranched conidiophores. Long chains of conidia were present. According to cytological and cultural findings, a presumptive identification of Paecilomyces spp. was made. The dog was treated with itraconazole 10 mg/kg/die for 3 months. A slight improvement was observed, afterwards a relapse occurred. The dog was euthanized and a necropsy was declined by the owner. At a later date the fungal isolate was subcultured for further analyses. After extraction of genomic DNA, sequences of the rRNA gene internal transcribed spacer (ITS) region were obtained using the sequencing primers ITS1 and ITS4 (Lindsley et al. 2001, J Clin Microbiol 39: 3505-3511). Following a GenBank BLAST search, DNA sequences showed a sequence similarity ranging from 97% to 99% to P. caninus strains described by Sigler at al. (2010). A retrospective morphological study of the isolates allowed recognizing the cultural features reported by the same authors (phialides narrow, cylindrical to slightly swollen at the base or below the midpoint and taper to a narrow neck with indistinct collarette; conidia borne in long chains or aggregate in heads, hyaline, smooth, subglobose, pyriform, obovoid or ovoid with a truncate base). The present report confirms this new species as another potential agent of canine infection. It also represents the first description of the morphological features of P.caninus in tissues, in which, as above described, this fungal species was shown to develop with highly pleomorphic elements.