Lack of Levofloxacin and Moxyfloxacin Efficacy in Experimental Plague of Albino Mice Infected with Nalidixic Acid Resistant Pathogen (Nal^r)

Abstract

The efficacy of levofloxacin and moxyfloxacin vs. the previously tested fluoroquinolones was studied on albino mice with experimental plague due to the Nalr mutants of Yersinia pestis 231 and 231 FI-. The plague microbe mutants resistant to nalidixic acid (Nalr) generated at a frequency of 10'10-10'9. The resistance to nalidixic acid was not accompanied by the strains loss of the virulence. The Nalr mutants were cross resistant to fluoroquinolones (ciprofloxacin, moxyfloxacin). The LD50 for the nontreated animals did not differ from that for the mice treated with nalidixic acid and the fluoroquinolones (when the animals were infected with Nalr mutants). The results showed that the criteria of the plague microbe susceptibility/resistance to fluoroquinolones should be revised.

Keywords

• experimental plague
• albino mice
• levofloxacin
• moxyfloxacin