Which statement correctly reflects the duration of antibiotic prophylaxis after exposure to inhalational anthrax?

• A. 7 days
• B. 60 days
• C. 14 days
• D. 90 days

Answer: (B)

The key idea is that the germination window for inhaled Bacillus anthracis spores can extend over several weeks, so postexposure antibiotics must be continued long enough to cover the chance that dormant spores may awaken and cause disease. Spore-containing inhaled particles can lodge in lymphoid tissue and germinate later, up to about 60 days after exposure. Therefore a 60-day course of prophylactic antibiotics provides protection through the entire potential germination period. Shorter durations (7 or 14 days) would leave a vulnerable window for infection to develop, while longer durations (90 days) add unnecessary extended antibiotic exposure without extra benefit in most cases. Thus 60 days is the standard recommended duration for post-exposure prophylaxis after inhalational anthrax exposure.