MICROBIOLOGY

• Mycobacteria spp. divided into rapid growers (< 7 days) and slow growers (>7 days) based on time to mature growth on agar plates.
• Rapid growing: M. fortuitum: (3-7 days) and M. chelonae. Slow growing: M. gordonae (7-10 days), M. malmoense, M. marinum (7-10 days), M. ulcerans and M. xenopi (3-8 wks in Cx), M. terrae, M. nonchromogenicum, (also: M. kansasii, M. avium-intracellulare, M. tuberculosis, not covered in this module).
• M. genavense: very slow growing. Alert lab: requires incubation in broth media for ≥8 wks.
• M. haemophilum: "blood-loving," slow growing. Alert lab: requires ferric iron supplementation and temperature 30^oC.
• Risk for non-tuberculous mycobacterial (NTM) disease in HIV+ pts directly proportional to CD4 count. Invasive non-TB disease rare with CD4 count >50 (except for M. marinum) and Sx usually chronic (>30 d) prior to Dx. High CD4 and short duration of Sx make NTM unlikely cause of illness; in this setting, positive sputum isolates more likely to be colonizers or contaminants.