Mycobacterium shottsii

Description

• Gram positive, acid-fast coccobacilli that may form cell aggregates in culture. Spores and cell branching are not present.

• Colonies on Middlebrook 7H10 agar are dysgonic, rough, non-pigmented and typically flat with an irregular margin, becoming umbonate upon ageing.
• Smooth colonies with an entire margin are seen less frequently.

• Visible colonies from a dilute inoculum are observed after 4–6 weeks incubation at 23 °C.
• Little or no growth occurs at 30 °C and none at 37 °C or above.
• Isolates do not grow on MacConkey agar or with 5% NaCl, are negative for arylsulfatase, b-galactosidase, nitrate reductase, pyrazinamidase, semiquantitative catalase, Tween 80 hydrolysis and Tween opacity and have variable reactions for acid phosphatase and catalase at 68 °C.
• The type strain is resistant to p-aminosalicylic acid and isoniazid but susceptible to ethambutol, ethionamide, kanamycin, rifampicin and streptomycin in disc susceptibility tests.

• The 16S rRNA gene sequence is unique among species of Mycobacterium and is most similar to those of Mycobacterium ulcerans and Mycobacterium marinum.
• Isolate M175T could be differentiated from other slowly growing, non-pigmented mycobacteria by its inability to grow at 37 °C, production of niacin and urease, absence of nitrate reductase and resistance to isoniazid, thiacetazone and thiophene-2-carboxylic hydrazide.

  Pathogenesis

• Pathogenic to the striped bass.

  Type strain

• First isolated from granulomatous lesions in splenic tissue from a striped bass.
• Strain M175 = ATCC 700981 = JCM 12657 = NCTC 13215