Antimicrobial susceptibility of Francisella tularensis subsp. holarctica strains from Hungary, Central Europe

Objectives: Determining the in vitro susceptibility to 11 antibiotics of Francisella tularensis subsp. holarctica strains belonging to the phylogenetic group B.13, from different areas of Hungary. Methods: Twenty-nine F. tularensis strains isolated between 2003 and 2010 from free-ranging European brown hares (Lepus europaeus) and a captive patas monkey (Erythrocebus patas) were collected from different parts of Hungary and examined for antibiotic susceptibility with commercially available MIC test strips on modified Francis agar plates; values were interpreted according to CLSI breakpoints. Results: The strains were susceptible to aminoglycosides (MIC90 values: gentamicin, 0.75 mg/L; and streptomycin, 6.0 mg/L), tetracyclines (MIC90 values: tetracycline, 0.5 mg/L; and doxycycline, 1.0 mg/L), quinolones (MIC90 values: ciprofloxacin, 0.047 mg/L; and levofloxacin, 0.023 mg/L) and chloramphenicol (MIC90 value: 1.5 mg/L), i.e. antibiotics commonly used in therapy. Tigecycline (MIC90 value: 0.19 mg/L) and rifampicin (MIC90 value: 1.0 mg/L) were also active against F. tularensis strains, while resistance to erythromycin (MIC90 value: .256 mg/L) and linezolid (MIC90 value: 32 mg/L) was observed in all strains. Conclusions: Based on the results, quinolones are recommended as first choice therapy for F. tularensis infection. The in vitro susceptibility of the strains to tigecycline may encourage the application of this antibiotic as well. The similar antibiotic susceptibilities of the Hungarian strains belonging to different subclades of phylogenetic group B.13 indicates that strains from other Central and Eastern European countries belonging to this group might also have the same susceptibility profile