Intra-abdominal nocardiosis and scedosporiosis in a dog: case report and literature review

Abstract

A 2-y-old, intact female, mixed-breed dog was presented to the veterinary hospital with abdominal distension, anemia, and lethargy following a chronic history of nonspecific gastrointestinal signs. CBC and serum biochemistry revealed moderate nonregenerative anemia with neutrophilia, hypoalbuminemia, hyperglobulinemia, hypoglycemia, decreased urea and creatinine, and hypercholesterolemia. Abdominal radiographs and ultrasound revealed a large heterogeneous mesenteric mass and ascites. Abdominocentesis confirmed septic peritonitis with filamentous bacteria. Fine-needle aspiration of the mass yielded pyogranulomatous inflammation and hyphae. An exploratory laparotomy revealed a large cranial abdominal mass with granulomas present throughout the abdominal cavity. Due to the poor prognosis and disseminated disease, the owner elected euthanasia. Postmortem and histologic examinations detected intralesional mycetomas and bacterial colonies within the mesenteric masses. 16S ribosomal RNA gene PCR and sequencing using formalin-fixed, paraffin-embedded sections identified Nocardia yamanashiensis, Nocardioides cavernae, and Nocardioides zeicaulis. Fungal culture, PCR, and sequencing confirmed Scedosporium apiospermum. Our report highlights the importance of molecular methods in conjunction with culture and histologic findings for diagnosing coinfections caused by infrequent etiologic agents. Additionally, we provide a comprehensive literature review of Scedosporium apiospermum infections in dogs.

Keywords: Nocardia yamanashiensis; Nocardioides cavernae; Nocardioides zeicaulis; Scedosporium apiospermum; dogs; nocardiosis; peritonitis; scedosporiosis.

Figure 1.

Systemic nocardiosis, nocardioidiosis, and scedosporiosis coinfection in a 2-y-old mixed-breed dog. A. Fine-needle aspirate of a mesenteric mass. Numerous neutrophils surround dense mats of elongate, variably septate, 2.5–4-μm hyphae or pseudohyphae with occasional bulbous ends and thin colorless walls or capsules and granular blue-pink internal structures (arrowheads). Wright–Giemsa. Bar = 50 µm. B. Postmortem examination. An 11 × 12 × 6.5-cm tan, firm mass (asterisk) effaced the greater omentum between the greater gastric curvature and the left pancreatic lobe. The intestines were diffusely adhered (arrowhead). L = liver; S = stomach; Sp = spleen. C. The mass was granular on cut surface, with 0.1–0.3-cm, yellow necrotic foci, and extensive hemorrhagic areas (arrowheads). D = duodenum; LP = left pancreatic lobe; S = stomach. D. Subgross photomicrograph of the duodenum. The serosal layer and the mesenteric adipose tissue are markedly expanded by pyogranulomatous inflammation with intralesional mats of filamentous bacteria (sulfur granules; arrowheads). H&E. Bar = 1 mm.

Figure 2.

Photomicrographs of the mesenteric mass. A. Pyogranulomas surround central mats of radiating filamentous bacteria (sulfur granules; arrowhead) and central mats of large, non-pigmented fungi (mycetoma; asterisk). H&E. Bar = 200 µm. B. Fite-stained, 1-µm thick, filamentous, acid-fast bacteria. Bar = 50 µm. Inset: filamentous, acid-fast bacteria. Bar = 10 µm. C. The filamentous bacteria were variably gram-positive. Gram. Bar = 50 µm. D. The mycetomas were surrounded by macrophages and neutrophils. H&E. Bar = 20 µm. E. The fungal hyphae were non-pigmented, septate, 2–6-µm wide, branching, with 4–7-µm wide terminal bulbous dilations. Gomori methenamine silver. Bar = 20 µm. F. Fungal culture from mesenteric tissue. Inhibitory mold agar, 4 d. The growth of the mold started white and cottony, turning light-gray with age and had a tan reverse. Inset: KOH with Parker ink revealed copious branching, septate, hyaline hyphae.