B. anthracis is generally sensitive to penicillins; therefore,penicillin G is the first-line treatment. Penicillin, such as amoxi-cillin or amoxicillin/clavulanic acid, is effective for the treatment of cutaneous anthrax. But after October 2001, ciprofloxacin or doxycycline is usually recommended due to the possibility of genetically engineered penicillin-resistant anthrax strains. Patients with inhalational anthrax are treated with multidrug regimen of either ciprofloxacin or doxycycline along with at least one more antibiotic, such as vancomycin, imipenem, meropenem, chloramphenicol, rifampin, tetracycline, clinda-mycin, and aminoglycosides. Ciprofloxacin or doxycycline for 60 days is effective against cases of GI anthrax. Doxycycline is not suitable for use in suspected cases of anthrax meningitis, because it has poor penetration of the central nervous system. B. anthracis shows resistance to sulfonamides and extended-spec-trum cephalosporin.
Antimicrobial therapy makes lesions culture-negative within hours, but the clinical manifestations of anthrax are related to the effects of the anthrax toxins. Antibiotics are ineffective once the toxin is formed; however, they may reduce the case fatality rate.