A laboratory reports growth on Lowenstein-Jensen medium after 4 weeks of incubation at 37 degrees C. The colonies are dry, rough, wrinkled, firmly adherent to the medium, and buff coloured. This description corresponds to:

• A Mycobacterium chelonae
• B Mycobacterium avium complex
• C Mycobacterium gordonae
• D Mycobacterium tuberculosis ✓

Explanation

M. tuberculosis colonies on LJ medium are classically described as rough, tough, and buff coloured, eugonic (abundant) growth appearing after 2 to 8 weeks because the generation time is 14 to 20 hours. M. avium and M. gordonae produce smooth colonies, and M. chelonae is a rapid grower visible within about 7 days, so none matches the described morphology.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.