Feline cutaneous mycobacteriosis: a review of clinical, pathological and molecular characterization of one case of Mycobacterium microti skin infection and nine cases of feline leprosy syndrome from France and New Caledonia.

BACKGROUND: Ten cats with skin lesions characteristic of cutaneous mycobacteriosis were included in this retrospective clinical, pathological and molecular study. HYPOTHESIS/OBJECTIVES: The aim of this study was to identify the causative agent and to compare the clinicopathological features of these cases with those of previous studies. METHODS: Cats were from the south east of France (eight cases), central France (one case) and New Caledonia (South Pacific; one case). Criteria for inclusion were histological evidence of granulomatous dermatitis and/or panniculitis, with acid-fast bacilli within macrophages or extracellularly in regions of tissue necrosis. PCR targeting the 16S-23S internal transcribed spacer region and sequence analysis were performed using DNA extracted from formalin-fixed, paraffin-embedded tissues from all cases. RESULTS: All cats were presented with a history of alopecic to ulcerated nodules. Most cases had limited disease, with one to few nodules, while others (three cats) showed a more aggressive clinical course. Lesions from eight cats yielded a sequence consistent with Mycobacterium lepraemurium, while Mycobacterium microti was identified postmortem from the cutaneous lesion in the cat originating from central France and euthanized for its debilitating condition. No PCR product could be amplified from the remaining specimen. CONCLUSIONS AND CLINICAL IMPORTANCE: Based on this geographically restricted case series, feline leprosy in southern France is most likely to be caused by M. lepraemurium and presents as a generally self-limiting disease. Molecular testing is essential to assess zoonotic potential, because M. microti-induced cutaneous mycobacteriosis can resemble feline leprosy syndrome.

Ulcerated and nonulcerated nontuberculous cutaneous mycobacterial granulomas in cats and dogs.

BACKGROUND: Mycobacterial granulomas of the skin and subcutis can be caused by one of a number of pathogens. This review concentrates on noncultivable species that cause diseases characterized by focal granuloma(s), namely leproid granuloma (in dogs) and feline leprosy (in cats). Clinically indistinguishable lesions can be caused by tuberculous organisms (Mycobacterium bovis and Mycobacterium microti) and members of the Mycobacterium avium complex. Rapidly growing mycobacterial species that cause infection of the subcutaneous panniculus associated with draining tracts are not discussed. Disease caused by Mycobacterium ulcerans is an important emerging differential diagnosis for ulcerated cutaneous nodules in certain localized regions. CLINICAL LESIONS: Lesions comprise one or multiple nodules in the skin/subcutis. These are generally firm and well circumscribed, and typically become denuded of hair. They may or may not ulcerate, depending on the virulence of the causal organisms and the immune response of the host. DIAGNOSIS: The most inexpensive, noninvasive means of diagnosis is by submission of methanol-fixed, Romanowsky-stained smears to a Mycobacterium Reference Laboratory after detecting negatively stained or acid-fast bacilli on cytological smears. Scrapings of material from slides usually provide sufficient mycobacterial DNA to enable identification of the causal organism using sequence analysis of amplicons after PCR using specific mycobacterial primers. THERAPY: Therapy relies upon a combination of marginal resection of easily accessible lesions and treatment using two or three drugs effective against slowly growing mycobacteria, choosing amongst rifampicin, clarithromycin, clofazimine and pradofloxacin/moxifloxacin.