Postexposure Prophylaxis against Experimental Inhalation Anthrax

TLDR

Inhalation anthrax is a rare disease that is almost invariably fatal. The study evaluated whether a prolonged course of postexposure antibiotics, with or without vaccination, could protect monkeys exposed to a lethal aerosol dose of Bacillus anthracis after antibiotic discontinuation. Groups of ten monkeys received penicillin, ciprofloxacin, doxycycline, doxycycline plus vaccination, vaccination alone, or saline starting one day post‑exposure; antibiotics were given for 30 days and then stopped, while the vaccine was administered on days 1 and 15. Each antibiotic regimen fully protected animals during therapy and provided significant long‑term survival after drug cessation (e.g., penicillin 7/10, ciprofloxacin 8/9, doxycycline 9/10, doxycycline + vaccination 9/9, all P < .02), and combining antibiotics with vaccination also protected against rechallenge.

Abstract

Inhalation anthrax is a rare disease that is almost invariably fatal. This study determined whether a prolonged course of postexposure antibiotics with or without vaccination would protect monkeys exposed to a lethal aerosol dose of Bacillus anthracis when the antibiotic was discontinued. Beginning 1 day after exposure, groups of 10 animals were given penicillin, ciprofloxacin, doxycycline, doxycycline plus vaccination, vaccination alone, or saline. Antibiotics were administered for 30 days and then discontinued. Vaccine was given on days 1 and 15. Two animals died of causes other than anthrax and were not included in the statistical analysis. Nine of 10 controls and 8 of 10 animals given only vaccine died. Each antibiotic regimen completely protected animals while on therapy and provided significant long-term protection upon discontinuance of the drug (penicillin, 7 of 10 survived, P < .02; ciprofloxacin, 8 of 9 survived, P < .002; doxycycline, 9 of 10 survived, P < .002; doxycycline plus vaccination, 9 of 9 survived, P < .0002). Protection against rechallenge was provided by combining postexposure antibiotic treatment with vaccination.