Tuberculosis can be especially difficult to treat for which of the following reasons?


I. It is slow-growing. 
II. Multi-drug-resistant strains are becoming more common.
III. The presence of mycolic acid and cord factor in the cell wall.

• A. I & II.
• B. I & III.
• C. II & III.
• D. I, II, & III.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the nature of Mycobacterium tuberculosis, the bacterium that causes tuberculosis. It is known for its slow growth rate, which means it takes longer to multiply compared to many other bacteria. This slow growth affects how quickly antibiotics can act, as many antibiotics target actively dividing cells.
2. Step 2: Recognize the challenge posed by multi-drug-resistant (MDR) strains of tuberculosis. These strains have evolved resistance to the most effective first-line antibiotics, making treatment more complicated and requiring the use of second-line drugs that may be less effective, more toxic, or more expensive.
3. Step 3: Examine the unique cell wall structure of Mycobacterium tuberculosis, which contains mycolic acid and cord factor. Mycolic acid is a waxy lipid that makes the cell wall impermeable to many antibiotics and disinfectants, while cord factor contributes to the bacterium's virulence and ability to evade the immune system.
4. Step 4: Combine these factors to understand why tuberculosis treatment is difficult: the slow growth delays antibiotic effectiveness, drug resistance limits treatment options, and the protective cell wall reduces drug penetration and immune clearance.
5. Step 5: Conclude that all three reasons (I, II, and III) contribute to the difficulty in treating tuberculosis, which is why the correct answer includes all of them.