Use of axenic media to determine antibiotic efficacy against coxiella burnetii.

The traditional methods of measuring minimum inhibitory concentration (MIC) of antibiotics against Coxiella burnetii are time-consuming and technically difficult. The discovery of axenic media for C. burnetii culture provided an opportunity to determine the feasibility of using both broth dilution and an antimicrobial gradient method (Etest) as a convenient method of measuring MICs. The MICs for a range of antibiotics that have proven or potential use in the treatment of Q fever, namely doxycycline, ciprofloxacin, levofloxacin, moxifloxacin and co-trimoxazole, were measured. It was possible to measure MICs using both microdilution and Etest methods. MICs obtained were comparable to those from other methods. This study demonstrates the potential use of a relatively simple test to measure MIC in an organism that is difficult to culture.