Other atypical mycobacteria

MICROBIOLOGY

• M. celatum: slow growing (3-8 wks to culture), non-photochromogenic.
  • It may cause false-positive M. tuberculosis direct (MTD) test or ribosomal RNA test.
  • Found widely in the environment (soil, water, dust).
• M. genavense: very slow grower (42d average); difficult to grow; alert lab if M. genavense suspected.
  • Consider if AFB is growing poorly and Mtb, MAI probe negative.
  • Found in bird populations and ferrets.
  • Antimicrobial testing is often problematic due to poor culture growth.
• M. haemophilum: slow growing; alert lab if suspected since it requires hemin or iron to grow in culture and grows best at 28-30°C.
• M. malmoense: slow growing; most clinical isolates/reports are from northern Europe.
• M. mucogenicum: rapid grower (< 7 days in culture); sporadic contaminant in respiratory samples; water is the environmental reservoir.
  • Previously known as M. chelonae-like organism.
• M. simiae: growth may take 4-6 weeks on LJ slants.
• M. szulgai: scotochromogen at 37ºC and a photochromogen at 25ºC.