In vitro antibiotic susceptibility of Francisella tularensis isolated fromhumans and animals

The in vitro susceptibility of 38 strains of Francisella tularensis (biovar F. tularensis palaearctica) was determined using Etests on cysteine heart agar plates with 2% haemoglobin. All strains were susceptible to the antibi otics traditionally used to treat tularaemia, such as streptomycin (MIC90 4 .0 mg/L), tetracycline (MIC90 0.38 mg/L) and chloramphenicol (MIC90 0.38 mg /L), and to aminoglycosides, such as tobramycin (MIC90 1.5 mg/L) and gentam icin (MIC90 1.0 mg/L). The quinolones examined had low MIC(90)s: ciprofloxa cin, 0.016 mg/L; levofloxacin, 0.016 mg/L; grepafloxacin, 0.047 mg/L; and t rovafloxacin, 0.032 mg/L. in contrast, all the strains were resistant to be ta-lactams and azithromycin. Quinolones thus seem to be promising drugs for the treatment of tularaemia.