Rapid in vitro activity of telavancin against Bacillus anthracis and in vivo protection against inhalation anthrax infection in the rabbit model

TL;DR

Telavancin, a new antibiotic, effectively kills Bacillus anthracis in lab tests and protects rabbits from lethal anthrax infections better than existing treatments.

Contribution

Telavancin shows potent in vitro and in vivo efficacy against Bacillus anthracis, including complete survival in a rabbit model.

Findings

Telavancin had low MICs (0.06–0.125 μg/mL) against all 17 B. anthracis isolates tested.

Telavancin achieved 100% survival in rabbits infected with anthrax spores.

Telavancin cleared bacteria from blood and tissues more effectively than levofloxacin.

Abstract

Inhalation anthrax is the most severe form of Bacillus anthracis infection, often progressing to fatal conditions if left untreated. While recommended antibiotics can effectively treat anthrax when promptly administered, strains engineered for antibiotic resistance could render these drugs ineffective. Telavancin, a semisynthetic lipoglycopeptide antibiotic, was evaluated in this study as a novel therapeutic against anthrax disease. Specifically, the aims were to (i) assess in vitro potency of telavancin against 17 B. anthracis isolates by minimum inhibitory concentration (MIC) testing and (ii) evaluate protective efficacy in rabbits infected with a lethal dose of aerosolized anthrax spores and treated with human-equivalent intravenous telavancin doses (30 mg/kg every 12 hours) for 5 days post-antigen detection versus a humanized dose of levofloxacin and vehicle control. Blood samples were collected at various times post-infection to assess the level of bacteremia and antibody production, and tissues were collected to determine bacterial load. The animals’ body temperatures were also recorded. Telavancin demonstrated potent bactericidal activity against all strains tested (MICs 0.06–0.125 μg/mL). Further, telavancin conveyed 100% survival in this model and cleared B. anthracis from the bloodstream and organ tissues more effectively than a humanized dose of levofloxacin. Collectively, the low MICs against all strains tested and rapid bactericidal in vivo activity demonstrate that telavancin has the potential to be an effective alternative for the treatment or prophylaxis of anthrax infection.

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