Abstract: Objective To study the membrane permeability of Mycobacterium abscessus. Methods（0.05%） Tween-80 was added to the liquid culture which contains RFP of 1/5 MIC concentration to increase the cell membrane permeability.The growth of Mycobacterium abscessus strains that had different MIC to RFP were evaluated by measuring the optical density（OD） of the growing culture at 450nm.The ultrastucture of cell wall was oberseved by electron microscopy. Results OD₄₅₀ of Mycobacterium abscessus clinical drug-resistant strains in the culture that contained both RFP and Tween-80 was significantly smaller than that in the culture contain RFP only（P<0.05）.While for clinical drug-sensitive strain and Mycobacterium tuberculosis drug-resistant strain,there is no significant difference between the OD₄₅₀ in this two kinds of culture.There seem to be a thin layer of deep-dyed structure in the cell wall of resistant strains,while the cell wall was more homogeneous in susceptible strain. Conclusions Mycobacterium abscessus has lower cell membrane permeability.These Results can partly explain the reason of Mycobacterium abscessus resistant to RFP.

Key words: Mycobacterium abscessus, Rifampin, Drug resistance, Cell wall