Systemic infection of Mycobacterium avium subspecies hominissuis and fungus in a pet dog

Abstract

A 3-year-old neutered female poodle with a long history of dermatophytic skin disease was presented with lethargy, anorexia and progressive weight loss. Abdominal ultrasonography revealed markedly enlarged mesenteric lymph nodes and multiple hypoechoic foci in the spleen. Cytology of the mesenteric lymph nodes and spleen showed granulomatous inflammation with fungal organisms and negatively stained intracytoplasmic bacterial rods consistent with Mycobacteria spp. Based on culture, multiplex polymerase chain reaction and sequence analysis, the bacterium was identified as Mycobacterium avium subspecies hominissuis. Despite treatment with antibiotics, the dog's condition deteriorated, and it died approximately 3 weeks after first presentation.

Fig. 1.

Abdominal ultrasonography of the spleen and mesenteric lymph node of the dog. (A) Multiple hypoechoic areas were identified in the spleen and (B) enlarged mesenteric lymph node.

Fig. 2.

Gross morphology of the spleen and mesenteric lymph node of the dog. (A) Multiple white nodules were noted in the spleen. (B) The mesenteric lymph node was grossly enlarged.

Fig. 3.

Fine needle aspirates of the spleen and enlarged mesenteric lymph node of the dog. (A) Macrophages contain unstained rod-shaped mycobacteria in the spleen. Aqueous-based Wright, HP oil, × 1,000. Scale bar: 20 µm, enlarged. (B) Large numbers of acid-fast-positive intracytoplasmic bacilli were identified in the mesenteric lymph node. Ziehl-Neelsen stain, HP oil, × 1,000. Scale bar: 20 µm, enlarged. (C) PAS-positive oval to elongated hyphal structures were identified in the spleen. Periodic acid-Schiff stain, HP oil, × 1,000. Scale bar: 20 µm, enlarged.

Fig. 4.

Identification of mycobacterium avium subspecies hominissuis using gel electrophoresis separation of multiplex PCR products. Lane M, molecular ladder; lane 1, spleen from the patient; lanes 2–7, M. avium subspecies avium ATCC 35716, M. avium subspecies paratuberculosis ATCC 19698, M. intracellulare ATCC 13950, M. bovis AN5, M. tuberculosis H37Rv and M. avium subspecies hominissuis 104, respectively; and lane 8, distilled water (negative control).