Which Mycobacterium grows only at 35°C and is differentiated from other mycobacteria by its susceptibility to T2H?

Which Mycobacterium grows only at 35°C and is differentiated from other mycobacteria by its susceptibility to T2H?

• A. M. kansasii
• B. M. avium-intracellulare complex
• C. M. bovis
• D. M. tuberculosis

Answer: (C)

Understanding how temperature preference and chemical susceptibility help identify mycobacteria is key here. Some species in the tubercle bacillus group have very specific growth temperature ranges and respond differently to diagnostic reagents. If an organism grows only at about 35°C and shows susceptibility to the T2H reagent, that combination is characteristic of Mycobacterium bovis. This species is part of the M. tuberculosis complex but has a distinct phenotype compared with others in the group: a restricted growth temperature around 35°C and a positive reaction to T2H, which lab schemes use to distinguish it from organisms like M. tuberculosis, M. kansasii, and M. avium-intracellulare that have different temperature tolerances and different susceptibility patterns.

Understanding how temperature preference and chemical susceptibility help identify mycobacteria is key here. Some species in the tubercle bacillus group have very specific growth temperature ranges and respond differently to diagnostic reagents. If an organism grows only at about 35°C and shows susceptibility to the T2H reagent, that combination is characteristic of Mycobacterium bovis. This species is part of the M. tuberculosis complex but has a distinct phenotype compared with others in the group: a restricted growth temperature around 35°C and a positive reaction to T2H, which lab schemes use to distinguish it from organisms like M. tuberculosis, M. kansasii, and M. avium-intracellulare that have different temperature tolerances and different susceptibility patterns.