Mycobacterium tuberculosis — Microbiology

A 32-year-old woman from Delhi presents with a 3-week history of productive cough, fever, and night sweats. Chest X-ray shows cavitary lesions in the right upper lobe. Sputum smear microscopy is negative for acid-fast bacilli on two occasions. Which is the most appropriate next investigation to confirm Mycobacterium tuberculosis infection?

Which structural feature best distinguishes Mycobacterium tuberculosis from Mycobacterium leprae?

The electron micrograph shown above displays a cluster of rod-shaped bacteria. Based on their characteristic morphology and typical size, which of the following organisms is most likely depicted?

Which enzyme produced by Mycobacterium tuberculosis catalyzes the synthesis of mycolic acids and is essential for cell wall integrity?

A 28-year-old woman from Delhi presents with a 2-month history of cough, low-grade fever, and weight loss. She is a healthcare worker with recent exposure to a TB patient. Sputum smear microscopy (Ziehl-Neelsen stain) is negative on two occasions, but a culture on Middlebrook 7H10 agar grows small, buff-coloured colonies after 4 weeks. The isolate is niacin-positive, nitrate-positive, and catalase-positive (heat-labile). A subsequent drug susceptibility test shows resistance to isoniazid and rifampicin. Which of the following is the MOST appropriate next step in the management of this patient?