**Question:** DOC for Meningococcal chemoprophylaxis is -

A. Penicillin
B. Ceftriaxone
C. Azithromycin
D. Chloramphenicol

**Core Concept:**
Meningococcal disease is an infection caused by the bacterium Neisseria meningitidis, which can lead to meningitis, sepsis, and other severe complications. Chemoprophylaxis refers to the use of antibiotics to prevent the spread of infection in close contacts or high-risk individuals exposed to the bacterium. The drugs are divided into two categories:

1. Category A: These drugs are effective against all strains of N. meningitidis and are considered first-line options.
2. Category B: These drugs are less effective against all strains but are still useful options in specific situations.

**Why the Correct Answer is Right:**

Category A drugs are the preferred option for meningococcal chemoprophylaxis. In this case, the correct answer is **B. Ceftriaxone**, which belongs to the third-generation cephalosporin class. Ceftriaxone is a broad-spectrum antibiotic with good penetration into the cerebrospinal fluid (CSF), making it an effective option for both prevention and treatment of meningococcal disease. Ceftriaxone has a long half-life, allowing for a single dose administration, reducing the risk of adverse reactions and drug interactions.

**Why Each Wrong Option is Incorrect:**

A. **Penicillin (D)** is a narrow-spectrum antibiotic that is not effective against all strains of N. meningitidis. In fact, some strains are resistant to penicillin, rendering it an unsuitable choice for chemoprophylaxis.

C. **Azithromycin (C)** is a macrolide antibiotic with a lower efficacy against N. meningitidis compared to cephalosporins. Macrolides are less effective against gram-negative bacteria like N. meningitidis, which are the causative agents of meningococcal disease.

D. **Chloramphenicol (A)** is an older antibiotic with narrow-spectrum coverage against gram-negative bacteria, including N. meningitidis. Chloramphenicol has poor CSF penetration and a higher risk of side effects, making it an inferior option for chemoprophylaxis compared to ceftriaxone.

**Clinical Pearls:**

1. For chemoprophylaxis in close contacts of a patient with meningococcal disease, ceftriaxone is the preferred choice due to its broad-spectrum coverage, excellent CSF penetration, and minimal side effects. Ceftriaxone is administered as a single dose, minimizing the risk of adverse reactions and promoting patient compliance.
2. Penicillin is not recommended for meningococcal chemoprophylaxis due to its narrow-spectrum activity against gram-negative bacteria like N. meningitidis, as well as its limited CSF penetration.
3. Azithromycin is less effective against