Which antibiotic is used for diphtheria prophylaxis?

• A. Erythromycin or Penicillin benzathine
• B. Azithromycin only
• C. Clindamycin alone
• D. Doxycycline alone

Answer: (A)

Prophylaxis for diphtheria focuses on eliminating carriage of the bacteria in those exposed so that transmission to others is prevented. The antibiotic choices that effectively eradicate Corynebacterium diphtheriae in close contacts are erythromycin and penicillin G benzathine. Erythromycin is a classic option given for several days to clear carriage, and penicillin G benzathine is an effective alternative, especially in those who can't take macrolides. While other antibiotics like azithromycin can be used in some settings, the standard prophylaxis regimen relies on erythromycin or penicillin benzathine. Clindamycin and doxycycline are not preferred choices for diphtheria carriage eradication in this context.