Abstract: Objective To reduce the pollution in mycobacterium culture and increase mycobacterium detective rate. Methods Culture was made to the polluted specimens to determine the distribution of polluted microorganism species in a certain period,and predominant bacterial species were analysed.Accoding to different species of predominant bacterium,different predisposal ways(acid pretreated agent or increasing the concentration of sodium hydroxide) were employed to pretreat samples before mycobacterium culture.This methodological improvement was compared with normal predisposal methods. Results Pretreating sample with 5% sulfuric acid when it was predominantly polluted by gram negative intestinal bacterium or with high density sodium hydroxide when it was predominantly polluted by gram positive bacterium(including yeastlike bacterium) may decrease pollution risk from 6.5% to 2.4%. Conclusion Selectively applying predisposal Methods according to different species of predominant polluted microorganism in a certain period may effectively reduce mycobacterium mycobacterium culture.

Key words: Mycobacterium tuberculosis, Equipment contamination, Culture media