Journal Article

<i>In vitro</i> susceptibility of <i>Bacillus anthracis</i> to various antibacterial agents and their time–kill activity

A. Athamna, M. Massalha, M. Athamna, A. Nura, B. Medlej, I. Ofek, D. Bast and E. Rubinstein

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 53, issue 2, pages 247-251
Published in print February 2004 | ISSN: 0305-7453
Published online February 2004 | e-ISSN: 1460-2091 | DOI:
In vitro susceptibility of Bacillus anthracis to various antibacterial agents and their time–kill activity

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  • Medical Oncology
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Objectives: To investigate the in vitro acquisition of resistance to antibiotics by Bacillus anthracis.

Methods: The in vitro activities of 18 antibacterial agents against two strains of B. anthracis, the Sterne strain and the Russian anthrax vaccine strain ST-1, were tested by determining the MICs and by measuring the rates of antibiotic kill at 5× and 10× MIC.

Results: The fluoroquinolones ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin, the β-lactams penicillin G and amoxicillin, the macrolide clarithromycin, the ketolide telithromycin, as well as clindamycin, rifampicin and quinupristin/dalfopristin had MICs in the range of 0.03–0.25 mg/L. Minocycline had an MIC of 0.03 mg/L, as did penicillin, against the ST-1 strain. Ciprofloxacin had an MIC of 0.03 mg/L against both strains. Erythromycin, vancomycin and the oxazolidinone linezolid were less active (MIC 0.5–2.5 mg/L). Ceftriaxone was the least active, having an MIC of 8.0 mg/L. Chloramphenicol was inactive (MIC > 256 mg/L). Quinupristin/dalfopristin, rifampicin and moxifloxacin showed the most rapid bacterial killing, achieving a complete eradication of detectable organisms (2 log10 reduction within 0.5–3 h and 4 log10 reduction within 0.5–4 h for both strains at concentrations of 5× and 10× the MIC). The β-lactams and vancomycin demonstrated a 2–4 log10 reduction within 5–15 h. Ceftriaxone had a similar effect to penicillin and amoxicillin against the ST-1 strain, but a slower effect than these two β-lactams against the Sterne strain. The macrolides, tetracyclines and linezolid demonstrated a lower kill rate, while chloramphenicol did not kill at all.

Conclusions: These data expand on the spectrum of agents recommended for the treatment of anthrax (ciprofloxacin, penicillin G and tetracyclines) and add new options, such as other fluoroquinolones, amoxicillin, rifampicin and quinupristin/dalfopristin, as potential therapeutic agents.

Keywords: Keywords: anthrax, fluoroquinolones, macrolides, β-lactams

Journal Article.  3116 words. 

Subjects: Medical Oncology ; Critical Care

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