Antimicrobial susceptibilities of Austrian Francisella tularensis holarctica biovar II strains

The antibiotic susceptibilities of 50 Francisella tularensis subsp. holarctica biovar II strains isolated from hares and human patients from the eastern part of Austria were examined. Minimum inhibitory concentrations (MICs) of 24 antimicrobial agents were determined using Etests™ on cysteine heart agar plates supplemented with 10% sheep blood. All isolates were sensitive to tetracyclines, aminoglycosides, quinolones, chloramphenicol and rifampicin. Resistance was observed in all isolates against macrolides, penicillins and aztreonam. Bacteria were resistant to cephalosporins and carbapenems, except for 8% of strains investigated that were susceptible or intermediately susceptible. Our in vitro susceptibility data can be applied for the detection and comparison of resistance development and to provide in vitro data for the guidance of therapy.