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In vitro activity of chloramphenicol, florfenicol and enrofloxacin against Chlamydia pecorum isolated from koalas (Phascolarctos cinereus)

LA Black, DP Higgins and M Govendir

The University of Sydney


Objective: To determine the in vitro susceptibilities of koala isolates of Chlamydia pecorum to enrofloxacin and chloramphenicol, which are frequently used to treat koalas with chlamydiosis, and florfenicol, a derivative of chloramphenicol.

Methods: The in vitro susceptibilities were determined by culturing three stored isolates and seven clinical swabs of C.pecorum. Susceptibility testing was undertaken using cycloheximide-treated buffalo green monkey kidney cells in 96 well microtitre plates.

Results: The minimum inhibitory concentrations (MICs) for all isolates were 0.25–0.50μg/mL (enrofloxacin), 1–2μg/mL (chloramphenicol), and 1–2μg/mL (florfenicol). Minimum bactericidal concentration (MBC) values for five isolates were also determined and were within one two-fold dilution of MICs. The MICs and MBCs of these antimicrobials were within ranges previously reported for other chlamydial species.

Conclusion: When combined with previously published pharmacokinetic data, the in vitro susceptibility results support chloramphenicol as a more appropriate treatment option than enrofloxacin for koalas with chlamydiosis. The susceptibility results also indicate florfenicol may be an appropriate treatment option for koalas with chlamydiosis, warranting further investigation.


  • All
  • 2013
  • Biogeography
  • Biology
  • Chlamydia
  • Diet
  • Disease
  • Ecology
  • Ellis
  • Eucalyptus
  • Genetics
  • Habitat
  • Infection
  • Interventions
  • Koala
  • Lunney
  • Threats
  • Timms
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