Susceptibility of Bacillus anthracis to eleven antimicrobial agents including novel fluoroquinolones and a ketolide.

OBJECTIVES

To determine the susceptibility of southern African strains of Bacillus anthracis to new, investigational agents as well as conventional antibiotics.

MATERIALS AND

METHODS

The MICs of 26 isolates of B. anthracis from South Africa and Zimbabwe, as well as the Sterne vaccine strain and a type culture strain, were determined by agar dilution.

RESULTS

The most active antimicrobial agents were the novel ketolide ABT 773, new and conventional fluoroquinolones, and doxycycline; macrolides were intermediately active. The lack of activity of extended-spectrum cephalosporins against B. anthracis was confirmed.

CONCLUSIONS

Susceptibility to conventional antibiotics was in keeping with previous studies. Two new fluoroquinolones and a ketolide showed promising in vitro activity that would support their further evaluation in animal models of anthrax.