Feline mycobacterial disease in northern California: Epidemiology, clinical features, and antimicrobial susceptibility

BACKGROUND: Mycobacterial infections in cats are challenging to treat and incompletely described. HYPOTHESIS/OBJECTIVES: To describe the features of mycobacterial infections in cats from northern California. ANIMALS: Nineteen cats, all with nontuberculous mycobacterial (NTM) infections; 4 with Mycobacterium avium infection, 15 with rapid‐growing mycobacterial (RGM) infection. METHODS: Retrospective study. Cases with positive mycobacterial culture, species identification, and susceptibility testing were included. Descriptive statistics were used. Fisher's exact test and Mann‐Whitney U test were used for comparisons between M avium and RGM infections (P ≤ .05). RESULTS: Rapid‐growing mycobacterial cases included Mycobacterium smegmatis (9), Mycobacterium fortuitum (4), Mycobacterium abscessus (1), and Mycobacterium thermoresistibile (1). Mycobacterium avium infections were more likely than RGM infections to be disseminated (3/4 vs 0/15; P = .004). Disease of the skin/subcutis (15/15 vs 0/4; P < .001) and outdoor access (14/15 vs 0/4; P = .001) were primary features of RGM infections. Resistance to fluoroquinolones and aminoglycosides was common among M avium isolates. A high prevalence of resistance to third‐ and fourth‐generation cephalosporins was noted in RGM species. Death/euthanasia was noted only in M avium cases (3/4). Twelve of 15 cats with RGM infection had available follow‐up; 4 of these cats achieved remission. CONCLUSIONS AND CLINICAL IMPORTANCE: The most prevalent RGM species isolated from cats from northern California are M smegmatis and M fortuitum. Susceptibility to prescribed antimicrobials does not appear to guarantee treatment success. Combination drug treatment is recommended. Repeat culture and susceptibility testing should be performed when disease is persistent/relapsing.