Updated recommendations for antimicrobial prophylaxis among asymptomatic pregnant women after exposure to Bacillus anthracis.

The antimicrobial of choice for initial prophylactic therapy among asymptomatic pregnant women exposed to Bacillus anthracis is ciprofloxacin, 500 mg twice a day for 60 days. In instances in which the specific B. anthracis strain has been shown to be penicillin-sensitive, prophylactic therapy with amoxicillin, 500 mg three times a day for 60 days, may be considered. Isolates of B. anthracis implicated in the current bioterrorist attacks are susceptible to penicillin in laboratory tests, but may contain penicillinase activity. Pencillins are not recommended for treatment of anthrax, where such penicillinase activity may decrease their effectiveness. However, penicillins are likely to be effective for preventing anthrax, a setting where relatively few organisms are present. Doxycycline should be used with caution in asymptomatic pregnant women and only when contraindications are indicated to the use of other appropriate antimicrobial drugs.