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

Mycobacterial infections in cats are challenging to treat and incompletely described.

To describe the features of mycobacterial infections in cats from northern California.

Nineteen cats, all with nontuberculous mycobacterial (NTM) infections; 4 with Mycobacterium avium infection, 15 with rapid-growing mycobacterial (RGM) infection.

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).

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.

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.