In Vitro Antibiotic Susceptibilities of Francisella tularensis Determined by Broth Microdilution following CLSI Methods.

In vitro susceptibilities for 47 antibiotics were determined in 30 genetic diverse strains of Francisella tularensis by the broth microdilution method following Clinical and Laboratory Standards Institute (CLSI) methods. The F. tularensis strains demonstrated susceptibility to aminoglycosides, fluoroquinolones, and tetracyclines. There was a distinct difference in macrolide susceptibilities between A and B type strains, as has been noted previously. The establishment and comparison of antibiotic susceptibilities of a diverse but specific set of F. tularensis strains by standardized methods and the establishment of population ranges and MIC50/90 values provide reference information for assessing new antibiotic agents and a baseline to monitor any future emergence of resistance, whether natural or intentional.