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.