N-乙酰半胱氨酸对铜绿假单胞菌生物被膜影响的实验研究

Influence of N-acetylcysteine on Pseudomonas aeruginosa biofilm

目的研究N-乙酰半胱氨酸(NAC)单独作用对铜绿假单胞菌(PA)生物被膜(BF)形成的影响,以及与左氧氟沙星(LFX)合用对BF菌的清除作用。方法2005年6月至2006年6月在中南大学湘雅医院中心实验室中进行试验。扫描电镜(SEM)观察BF的形态,最小抑菌浓度(MIC)采用试管双倍稀释法测定;用甲基四氮唑蓝(MTT)比色法测定BF中活菌数。结果NAC能减少BF中基质样物质以及被膜的厚度,单用LFX需1MIC以上浓度才能使BF内活菌数明显下降。小剂量NAC(0.5g/L)与1/2MIC的LFX联合应用可使BF内活菌数明显下降,NAC对LFX的协同杀菌作用呈浓度依赖性。结论NAC能够抑制BF形成,并可增强LFX对PA生物被膜菌的杀菌活性。

Objective To observe the influence of N-acetylcysteine（NAC） on the formation of Pseudomonas aeruginosa biofilm（BF） ,and to study the synergism of bactericidal activities of NAC combined with levofloxacinon to the mature Pseudomonas aeruginosa biofilm. Methods The experiment was done in experiment centre of Xiangya Hospital. Scanning electronic microcopy（SEM） were utilized to demonstrate the effect of NAC on the formation of biofilm. Then biofilm cultured without NAC were detected by optical microscopy after being stained with AgNO3. The minimal inhibitory concentration were detected by double test tube diluted method. The mature biofilm was treated by NAC and/or different concentrations of levofloxacin for 24 hours. The influence of levofloxacin combined with NAC were examined by MTT method on the bacterial quantity in biofilms. Results Biofilm was achieved on the silicon slides in all groups 7 days after the incubation of Pseudomonas aeruginosa. Scanning electronic microcopy showed that the mucoid materials among bacteria was significantly reduced and the thickness of biofilm was decreased in NAC groups. Levofloxacin beyond 1 MIC could significantly decline the viable cells on biofilms（ P 〈0. 05）. However,0. 5g/L NAC combined with 1/2MIC levofloxacin could also significantly decline the viable cells on biofilms （ P 〈 0. 05 ）. The synergistic effect of NAC lied on its concentration. NAC without levofloxacin could not decrease the bacterial quantity in mature biofilm. Conclusion NAC has no direct bactericidal activities to Pseudomonas aeruginosa in biofilms, but NAC can reduce bacterial biofilm formation and enhance LFX bactericidal activity reduction in mature biofilm viable cells.