Which of the following mycobacteria has an optimal growth temperature 30-32°C?

• A. M. avium complex
• B. M. bovis
• C. M. ulcerans
• D. M. xenopi

Answer: (C)

Different mycobacteria grow best at different temperatures because they’re adapted to distinct environments. Mycobacterium ulcerans, which causes Buruli ulcer, is tailored to cooler aquatic settings and thus has an optimal growth temperature around 30–32°C. Under these conditions its colonies appear more readily, whereas at body temperature (around 37°C) or higher temps growth is reduced.

In contrast, the other species mentioned are more comfortable at 37°C or higher: M. avium complex and M. bovis generally grow well at human body temperature, and M. xenopi is thermophilic, often requiring higher temperatures (around 42°C) for robust growth. So the organism whose optimal growth sits in the 30–32°C range best fits the question.