Figure 3. A photomicrograph of a renal core biopsy sample showing septate hyphae with roughly parallel walls and occasional
branching (Grocott-Gomori methenamine-silver nitrate stain; 400X; bar = 50 μm).
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After 25 days, Paecilomyces species was identified on the fungal culture (inhibitory mold agar) of the pyelocentesis-collected urine sample. Histologic
samples were then re-reviewed, and some morphologic features of the hyphae were noted to be indicative of Paecilomyces species rather than Aspergillus species. These included some nondichotomous branching, generally narrow diameters (most often 3 μm), and slight tapers or
bulges in some areas of the hyphae (i.e. focal absence of parallel walls).1
Discussion
Paecilomyces species are found in soil and decaying vegetation worldwide. The genus Paecilomyces has mycelia that have broad, branching, septate hyphae with characteristic phialides swollen at the base. Colony size, color,
and rate of growth vary among species.2 Members of this genus are often encountered in clinical microbiology laboratories as contaminants. Nevertheless, many cases
have been reported in which the role of this fungus as a pathogen has been clearly demonstrated. These infections are referred
to as paecilomycosis (a subtype of the hyalohyphomycosis group).
Disseminated paecilomycosis has been reported in dogs, a cat, rats, reptiles, a rhesus monkey, horses, and people.2-18 Additionally, Paecilomyces species are among the many emerging causative agents of opportunistic mycoses in immunocompromised people (most commonly
associated with cutaneous infections, catheter-related fungemia, sinusitis). Most published case reports of paecilomycosis
among otherwise healthy, nonimmunocompromised people have been infections involving the cornea, prosthetic lens implants,
lacrimal sacs, maxillary sinuses, prosthetic mitral and aortic valves, the skin, and the peritoneum.2,17,18
In the veterinary literature, paecilomycosis most commonly affects dogs, with the disease typically manifesting as a systemically
disseminated form or as diskospondylitis.3-11,16 In some animals, localized cutaneous disease is the only clinical sign of occult disseminated disease.3,12 The German shepherd is the breed most commonly affected with paecilomycosis or other systemic mycosis.15,19 Adult female dogs make up more than 90% of the reported cases of paecilomycosis in dogs.16 The areas most commonly involved in disseminated paecilomycosis are intervertebral disks, the liver, the spleen, visceral
or peripheral lymph nodes (e.g. pancreatic, iliac, inguinal, renal, hepatic, mesenteric, sublumbar, cranial mediastinal, hilar, peritracheal, prescapular,
and popliteal), and the kidneys.11
Paecilomyces species infection has been reported in two cats. One cat presented with local skin lesions that progressed into disseminated
paecilomycosis after two months. This cat was treated with ketoconazole for three months without success.12 The second cat was 5 years old and had localized recurrent cutaneous infections of the left metacarpal region and upper
lip. The cat was successfully treated with multiple excisions of the affected cutaneous tissues, débridement of surrounding
tissues, and postoperative treatment with itraconazole.13
The location of the primary lesion in systemic paecilomycosis is not usually determined in animals. The authors of previously
reported cases suspected cutaneous or mucosal wounds.3,5-7,9-12 The fungus can spread to different locations and progress slowly. Our patient had a history of skin allergies. It had been
treated with prednisone and desensitization injections. It is possible that the prednisone and desensitization predisposed
the dog to Paecilomyces species colonization. However, the route of entry of the fungus in our patient is unknown.
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