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Which anti tubercular drug crosses the blood brain barrier (BBB)?

# Which anti tubercular drug crosses the blood brain barrier (BBB)?

A. INH

B. Rifampicin

C. Ethambutol

D. Streptomycin

The correct answer is A. INH (Isoniazid).

Explanation:

INH (Isoniazid):

- Crosses the blood-brain barrier (BBB) effectively, even in the absence of inflammation.

- First-line drug for tuberculous meningitis due to excellent CSF penetration.

- Critical for treating CNS tuberculosis.

Other Options:

B. Rifampicin: Penetrates the BBB only when meninges are inflamed (e.g., in active meningitis). Not as reliable as INH under normal conditions.

C. Ethambutol and D. Streptomycin: Poor BBB penetration, making them unsuitable for CNS tuberculosis.

Key Takeaway:

INH is the most reliable anti-tubercular drug for crossing the BBB, especially in latent or early CNS infections. Rifampicin’s efficacy depends on meningeal inflammation.

Which of the following can be diagnosed using dark field microscopy?

# Which of the following can be diagnosed using dark field microscopy?

A. Spirochaetes

B. Streptococci

C. Corynebacteria

D. Mycobacteria

The correct answer is A. Spirochaetes.

Explanation:

Dark field microscopy is particularly useful for observing organisms that are difficult to stain, such as Spirochaetes (e.g., Treponema pallidum, the causative agent of syphilis). These bacteria are thin and motile, making dark field microscopy ideal for visualizing their morphology and movement.

Streptococci (B), Corynebacteria (C), and Mycobacteria (D) are typically diagnosed using Gram staining, Albert staining, or acid-fast staining, respectively. They do not require dark field microscopy.