A slow-growing, non-pigmented mycobacterium isolated from a lymph node biopsy is photochromogenic (develops yellow pigment on exposure to light). It grows optimally at 30°C and causes scrofula in children. Which organism is this?

• A Mycobacterium marinum
• B Mycobacterium scrofulaceum ✓
• C Mycobacterium avium complex
• D Mycobacterium gordonae

Explanation

Mycobacterium scrofulaceum is a slow-growing photochromogenic NTM that grows better at 30°C and is a classic cause of pediatric cervical lymphadenitis (scrofula). M. marinum is photochromogenic but causes swimming pool granuloma and grows at 30-32°C; it is less commonly associated with scrofula. MAC is non-photochromogenic. M. gordonae is a tap water contaminant, non-pathogenic, and grows at 37°C.

Reference: Koneman's Color Atlas and Textbook of Diagnostic Microbiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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