EFFICACY OF DOXYCYCLINE AND CIPROFLOXACIN AGAINST EXPERIMENTAL YERSINIA-PESTIS INFECTION

The efficacies of ciprofloxacin and doxycycline prophylaxis and therap y were assessed against experimental pneumonic plague infections induc ed by two strains of Yersinia pestis in a mouse model. When exposed to an aerosol of Y. pestis strain GB, containing 8.39 x 10(5) +/- 4.17 x 10(4) cfu, the retained dose was 7.3 x 10(3) +/- 2.3 x 10(3) cfu. Whe n exposed to an aerosol of Y. pestis strain CO-92, containing 1.86 x 1 0(5) +/- 7.4 x 10(3) Cfu, the retained dose was 3.4 x 10(4) +/- 2.6 x 10(3) cfu. Both strains resulted in a respiratory and systemic infecti on closely resembling human pneumonic plague. Ciprofloxacin prophylaxi s and therapy was successful against both strains for up to 24 h after challenge, but not after 48 h. Both doxycycline prophylaxis and thera py regimens were ineffective against both strains, although strain CO- 92 was more susceptible in vitro to doxycycline than strain GB and sup ra-MIC levels were achieved in the serum and lungs of the animal.