CASE REPORT: Disseminated nocardiosis caused by Nocardia abscessus in a dog

Abstract

A 4-year-old female spayed Bichon Frise dog that had been receiving cyclosporine A per os 3 times per week for 2 months to control allergic dermatitis developed lethargy, anorexia, fever, and multiple firm subcutaneous masses. Pyogranulomatous inflammation with branching nonseptate filamentous organisms approximately 2 μm in diameter, presumptively fungal organisms, was diagnosed by cytologic evaluation of fine-needle aspirates from several masses. A partially acid-fast actinomycete was cultured from 2 of the masses. The organism was identified as Nocardia abscessus (formerly Nocardia asteroides type 1) based on 16S ribosomal DNA sequencing of samples extracted from cultures and unstained cytologic smears. Immunosuppression caused by long-term administration of cyclosporine A likely predisposed the dog to disseminated infection. To our knowledge, this is the first report of N. abscessus infection in a dog. This case demonstrates that N. abscessus may be mistaken for a fungal organism based on its cytologic appearance and underscores the importance of using molecular techniques for the diagnosis of suspected fungal diseases.

Cutaneous nocardiosis in two dogs receiving ciclosporin therapy for the management of canine atopic dermatitis

“…Immunosuppression appears to be a predisposing factor for the development of nocardiosis in humans and cats, although both healthy and immunocompromised individuals can be affected . In dogs, infection occurs predominantly in immunocompromised individuals secondary to the administration of immunomodulatory drugs, including ciclosporin combined with or without ketoconazole, prednisolone, dexamethasone, cyclophosphamide, azathioprine, chlorambucil and aurothioglucose …”

The polymerase chain reaction in the diagnosis of infectious diseases

“…One of the most frequent diagnostic applications of PCR is in the detection of infectious agents. Several recent publications in Veterinary Clinical Pathology describe the use of PCR to successfully detect DNA from a variety of pathogens, including bacteria, 3–5 viruses, in which PCR detected the proviral DNA of feline retroviruses, 6,7 protozoa, 8–10 and fungi 11 …”

“…Many infectious disease diagnostic PCR assays target specific species, and knowledge of the DNA sequences of these species is required to enable the development of the PCR assays 8,12 . In the current issue of VCP , however, MacNeill and colleagues describe a case of disseminated Nocardia abscessus infection in a dog in which PCR was also used successfully to confirm the presence of an unknown infectious agent 4 . The authors used “universal” PCR assays for bacteria or fungi; these assays use PCR primers that are designed to anneal to DNA sequences, in this case the 16S rRNA and 18S rRNA genes for bacteria and fungi, respectively, that are highly conserved across all bacteria or fungi.…”

“…PCR also has the advantage of being applicable to a variety of clinical samples. Recent articles in VCP report the use of blood, 6,12 ascitic fluid, 8 cytologic smears and culture specimens, 4 and bronchoalveolar lavage samples 11 for successful DNA extraction for PCR. Paraffin‐embedded fixed tissues may also be used, particularly for real‐time PCR due to the small amplicon size, limiting the influence that any structural damage to the DNA has on subsequent PCR amplification 14 .…”

“…Paraffin‐embedded fixed tissues may also be used, particularly for real‐time PCR due to the small amplicon size, limiting the influence that any structural damage to the DNA has on subsequent PCR amplification 14 . Additionally, PCR can be advantageous for identification of organisms that are slow 4 or impossible 12 to grow in vitro.…”