Objective To investigate the induction of L-forms of Yersiniapestis by enrofloxacin,in order to know more about the formation conditions and biological characteristics of L-form Yersinia pestis.Methods Yersinia pestis EV were cultured in Hiss agar media containing 0,0.5,5,10,50,100,500 and 1 000 ng/mL enrofloxacin respectively.The cultures containing 50 ng/mL enrofloxacin was subcultured in Hiss agar media without enrofloxacin for reversion.The colonial morphology of each sample was observed.The bacterial morphology was observed by Gram staining and cell wall staining,while the cell wall integrity by transmission electron microscope.Yersinia pestis EV and L-form Yersinia pestis were identified by 16S rDNA,analyzed for the homology and the phylogenetic tree were constructed.Results Enrofloxacin 0.5 ng/mL contained in Hiss agar media caused morphological changes of Yersinia pestis,from typical short-rod to long-rod shape.When the concentration of enrofloxacin was 50 ng/mL,the cell wall of Yersinia pestis was deficient,and the bacteria could not divide and proliferate normally,but showed long-rod shape and coiled into a mass,with the colonial morphology like fried eggs.Enrofloxacin-induced L-form Yersinia pestis reversed in normal Hiss agar media,and displayed a typical Yersinia pestis short-rod shape.16S rDNA identification showed that the homology between the induced strain and the parent EV strain before induction was 100％.Conclusion Enrofloxacin can induce the L-forms of Yersinia pestis.
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