大肠杆菌耐药性抑制剂作用机制的初步研究

20株人源和动物源性大肠杆菌在体外经黄连提取物(命名为耐药性抑制剂IT2)作用后,对氟喹诺酮类抗菌药、庆大霉素和多西环素的耐药性明显被抑制.选取经抑制剂IT2作用后耐药性变化显著的5对菌株进行质粒提取和电泳检测,发现J0、H004、J3、J2 等4株菌作用前均有质粒带,与其相对应的耐药性抑制剂作用后的菌株ITJ0、ITH004、ITJ3、ITJ2质粒带全部消失,只有菌株J1经抑制剂IT2作用前后质粒带无变化.提取外膜蛋白进行SDS-PAGE电泳分析,菌株J1、J3、J0缺少OmpF、OmpA, J2仅缺少OmpA,经耐药性抑制剂作用后,J1、J3、J0的OmpF均由缺失恢复为表达,OmpC的表达量呈显著增加,H004没有变化.结果表明耐药性抑制剂IT2对大肠杆菌的部分耐药性具有良好的抑制作用,其作用与阻碍耐药质粒拷贝、恢复外膜通道蛋白正常表达关系密切.

Study on molecular mechanisms of drug-resistant inhibitors in Escherichia coli

Twenty multi-drug resistant strains of pathogenic E.coli isolated from clinical samples of patients and sick chicken were cultured in LB which contained certain concentration of the extracts of coptis root (named inhibitor IT2). Five pairs of strains(before treatment and after treatment) were selected to be extracted plasmids and outer membrane proteins (OMP) because their characteristics of resistance to fluoquinolones, gentamicin, deoxycycline changed apparently. Detection with agarose electrophoresis, strains J0,H004,J3 and J2 all had resistant plasmids,while strains ITJ0,ITH004,ITJ3,ITJ2 (treated with inhibitor IT2) did not have any plasmids. Only plasmid of strain J1 was not eliminated by inhibitor IT2. SDS-PAGE showed that OMPs of strains J1,J3 and J0 all lacked of OmpF and OmpA, J2 lacked of OmpA. After being treated with IT2, strains J1,J3 and J0 recovered to express OmpF,the quantity of OmpC was increased. There was only strain H004 was not found any changes in OMPs. As a result, inhibition effects of IT2 may be associated with the elimination of resistant plasmids and the recovery of normal expression of OMPs.