Observations Of Properties And Drug Resistance Of The L-form Of M.tuberculosis Induced By The Antituberculosis Drugs

Objectives To investigate the mechanism of generation of L-form of M.tuberculosis and its significance on the development,diagnosis and treatment of tuberculosis.Methods M.tuberculosis was inoculated into the BD 960 liquid medium with isoniazid(0.01、0.04、0.08 ug/m L),rifampin(0.05、0.1、0.2 ug/m L)or ethambutol(1、2.5、5 ug/m L)and then the L-form was observed by microscopy ten days later.The cultures were filtrated to get the pure cultures of stable L-form by subculture with the modified TSA-L medium and characteristics of morphology,growth and susceptibilities to the antibacterial drugs of M.tuberculosis were observed when the pure subcultures of the L-form were isolated.Results L-form of.tuberculosis was induced by the concentrations of rifampin,isoniazid or ethambutol.The L-form would not be susceptible to the above mentioned antituberculosis drugs but susceptible to macrolides and quinolones.The morphologies of L-form were irregular spherical or round.The L-form was positive or negative by Gram stain.Conclusions M.tuberculosis could be killed by rifampin,isoniazid or ethambutol but also could be induced to become the L-form by these antituberculosis drugs,and it is one of the important factor that affecting the effect of treatment of the tuberculosis.It is recommended that the L-forms should be noticed during the treatment with the antituberculosis drugs and combination treatment with antituberculous drugs to which the L-forms were susceptible,is also very important.