Efficacy of Levofloxacin, Lomefloxacin and Moxifloxacin vs. Other Fluoroquinolones in Experimental Plague Due to FI+ and FI- Strains of Yersiniapestis in Albino Mice

Abstract

Activity of levofloxacin, lomefloxacin and moxifloxacin against 20 FI⁺ and 20 FI^- strains of Yersinia pestis was studied. It was shown that the strains were highly susceptible to the fluoroquinolones. In the experiments on mice subcutaneously infected with suspension of strains 231 FI⁺ and 231 FI^- of Y.pestis in a dose of about 1000 LD₅₀ (10⁴ microbial cells) the ED₅₀ of levofloxacin and moxifloxacin was 5.5-14.0 mg/kg independent of the infective culture phenotype and that of lomefloxacin was 18.5 mg/kg. Estimation of the impact of the pathogen infective dose value on the results of the experimental plague treatment with the therapeutic dose equivalent to the human one showed high efficacy of the fluoroquinolones (efficacy index of 10⁴). The treatment for 7 days provided 90-100-percent survival of the animals. The prophylactive use of lomefloxacin (in 5 hours - 5 days) was less efficient (70-80% of the survivals) in the animals infected with the antigen-changed (FI^-) variant of the pathogen. Levofloxacin and moxifloxacin provided 90-100-percent survival of the animals treated for a course of 5 days independent of the pathogen phenotype. The study demonstrated that the use of levofloxacin, lomefloxacin and moxifloxacin was prospective for the prophylaxis and therapy of experimental plague.