Abstract
Mycobacterium avium-intracellulare complex infections are becoming an increasing concern in veterinary medicine because they affect livestock, wildlife, and companion animals. Here we describe the isolation, molecular typing, and antibiotic susceptibility testing of the causative agent of a rare case of generalized mycobacteriosis in a crossbred dog. Mycobacterial colonies were isolated from a popliteal lymph node aspirate sample and molecular typed by SNPs typing of the genes gyrB and rpsA, the 3′ region of the hsp65 gene and the internal transcribed spacer (ITS), and MIRU-VNTR analysis. Colonies were also tested in vitro against the macrolide clarithromycin and other drugs, using a resazurin microdilution assay, in order to provide the most appropriate treatment for the dog. Results from SNPs typing of gyrB and ITS, as well as from MIRU-VNTR analysis suggested the isolation of a single strain of M. avium subsp. hominissuis (Mah). On the other hand, SNP typing of rpsA revealed DNA polymorphisms that led colonies to cluster into two groups. The presence of two distinct strains of Mah has been assumed. All colonies, regardless of the nucleotide sequence of rpsA, were found to be sensitive to all of the drugs tested except for ethambutol. Although the therapy administered was adequate, the dog's overall clinical status worsened progressively and the animal died 8 months later. In conclusion, we report on the isolation of Mah from a dog with generalized mycobacteriosis.
Highlights
Mycobacterium avium-intracellulare complex (MAC) infections are becoming an increasing concern in veterinary medicine because they occur in a wide range of animals, including domestic animals [1], ruminant and non-ruminant wildlife [2], and companion animals [3, 4]
We report the results of the investigation of a rare case of disseminated mycobacteriosis in a crossbred dog
We describe here a rare case of generalized mycobacteriosis in a crossbred dog where the results of an in-depth molecular investigation suggested an infection with two distinct isolates of M. avium subsp. hominissuis (Mah)
Summary
Mycobacterium avium-intracellulare complex (MAC) infections are becoming an increasing concern in veterinary medicine because they occur in a wide range of animals, including domestic animals [1], ruminant and non-ruminant wildlife [2], and companion animals [3, 4]. M. avium, the most clinically significant in both humans and animals, comprises four subspecies: M. avium subsp. Many cases of canine MAC infection discussed in the literature have not been typed at subspecies level [4, 8]. We have no accurate data concerning the pathogenicity of MAC subspecies in these companion animals. In a few cases, molecular typing at subspecies level has been carried out and Mah has proved to be the most frequent isolate [6, 7, 9]
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