Mycobacterium nebraskense infection in a dog in Switzerland with disseminated skin lesions

Background Cutaneous disseminated mycobacteriosis is rare in dogs. To the best of the authors’ knowledge, the slowly growing mycobacterial species Mycobacterium nebraskense has not been described before in this species. Objective Description of clinical features, laboratory analyses and treatment regimen of this unusual case. Animal A 9‐year‐old female‐spayed West Highland white terrier dog presented with progressive nodules and ulcerations on both sides of the thorax and the rostral aspect of the chest. Methods and materials Investigations involved histopathological examination of skin biopsies (including special stains for fungi, bacteria and mycobacteria), standard and mycobacterial culture (including susceptibility testing), 16S/23S rRNA sequencing and BLAST similarity searching. Results Ziehl–Neelsen staining of decontaminated biopsy material revealed acid‐fast bacteria morphologically consistent with mycobacteria. Treatment with clarithromycin and marbofloxacin achieved partial resolution. A change in the treatment regimen to pradofloxacin and azithromycin resulted in rapid deterioration of skin lesions. Final healing occurred with the addition of prednisolone at an anti‐inflammatory dose. The results of mycobacterial culture and susceptibility testing were received 10 and 12 months, respectively, after the first presentation of the dog. Therapy was stopped after 16 months without recurrence of skin lesions. Conclusions and clinical importance This case is noteworthy for the description of a new mycobacterial species contributing to disseminated panniculitis in a dog and for the difficulties experienced in the lengthy empirical treatment of slowly growing nontuberculous mycobacterial infections. The addition of prednisolone to induce complete healing raises the question of whether the mycobacterial infection was primary or whether it occurred secondarily to an ongoing sterile panniculitis.