Three weeks after cosmetic liposuction at a clinic, a 30-year-old woman develops multiple erythematous nodules and a draining sinus over the abdomen. Ziehl-Neelsen stain shows acid-fast bacilli, and cultures show growth within 5 days on Lowenstein-Jensen medium. Which property best characterizes the causative organism?

• A It requires glycerin-enriched media and grows only at 32 degrees Celsius
• B It cannot be cultured on routine bacteriological media and needs Middlebrook agar
• C It produces cord factor and is niacin positive like M. tuberculosis
• D It belongs to Runyon group IV and is innately resistant to standard antitubercular drugs ✓

Explanation

Growth within about 7 days identifies a rapid grower, placed in Runyon group IV, which includes M. fortuitum, M. chelonae and M. abscessus. These organisms cause post-injection and post-surgical skin and soft tissue infections through contaminated instruments or water. They are inherently resistant to conventional first-line antitubercular drugs and require macrolides, amikacin or fluoroquinolones based on susceptibility testing.

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.