MICROBIOLOGY

• Slow-growing long acid-fast bacillus (AFB), non-tubercular mycobacteria (NTM).
  • Growth on Löwenstein-Jensen media or Middlebrook 7H10 agar is typically seen > 7 days at 37ºC, although 25ºC is optimal.
    • It will not grow if ethambutol (1 mg/L) or INH (10 mg/L plus normal saline present.
  • Scotochromogenic (smooth yellow to orange colonial formation, Fig) if growing in the presence of light.
  • Old classification: Runyon Group 2.
• Ubiquitous; the reservoir is water (natural and tap) and soil. Often referred to as the "tap water bacillus."
  • Also described in pools, unpasteurized milk, healthy human secretions
• Growth usually takes three weeks or more at 37°C.