Treatment for Rocky Mountain spotted fever in children is best with which antibiotic?

• A. Doxycycline
• B. Amoxicillin
• C. Erythromycin
• D. Azithromycin

Answer: (A)

RMSF is caused by an intracellular bacterium that invades endothelial cells, so the antibiotic chosen must penetrate cells well and effectively halt bacterial protein synthesis. Doxycycline fits this need, binding the bacterial 30S ribosomal subunit and blocking protein synthesis, which makes it highly effective against rickettsial organisms. Because RMSF can progress rapidly and be fatal, treatment should be started promptly when suspicion is high, even before confirmatory tests. In children, the historical concern about teeth staining is outweighed by the serious risk of RMSF, and doxycycline remains the preferred option since other common antibiotics (like amoxicillin or macrolides) do not reliably treat rickettsiae. If doxycycline cannot be used, chloramphenicol is an alternative, though it carries significant toxicity and is not first-line.