大肠杆菌质粒与喹诺酮耐药性关系的研究

摘要

Thirty two ofloxacin-resistant strains of chicken pathogenic E.coli were isolated from clinical samples. All strains were cultured in LB culture medium containing eliminator berberini sulfatis (BS) or ethidium bromide (EB) for 24 or 48 hours. The levels of quinolone resistance of four strains were clearly reduced after treatment. Plasmids of these four strains were extracted and tested with electrophoresis, only the plasmids of strain CE01, of which the transfer of plasmids was associated with quinolone resistance, had been eliminated by BS or EB, while there were no changes in plasmids after treated with eliminators in the others. Concentration of the plasmid electrophoretic band of CE01XC1, which could not grow in the culture medium containing ofloxacin 20μg/mL, discreased significantly then the bacteria were treated with BS for 24h; the band of CE01XC2 disappeared when they were cultured in the same medium as CE01XC1 for 48h; the band concentration of CE01XC3, which grew well in the culture medium containing ofloxacin 20μg/mL, hardly changed. The results suggest that strain CE01 has a plasmid which is associated with quinolone resistance.%为研究大肠杆菌质粒与喹诺酮耐药性的关系，临床分离32株耐喹诺酮药物的致病性大肠杆菌，经质粒消除剂溴化乙淀（EB）、硫酸黄连素（BS）分别处理24h和48h，其中4株对喹诺酮的耐药水平明显降低。经消除剂作用的菌株提取质粒进行电泳检测，结果只有大肠杆菌CE01［其中氧氟沙星（OFL）的最小抑菌浓度(MIC)>50μg/mL］的质粒带发生变化，且该质粒的转移与喹诺酮抗性有关。经消除剂BS作用24h，在含OFL 20μg/mL的琼脂不能生长的CE01XC1菌株其质粒带浓度显著降低；作用48h后，在含OFL 20μg/mL琼脂不能生长的CE01XC2菌株其质粒带被消除；BS作用48h后在含OFL 20μg/mL琼脂仍然生长的CE01XC3菌株其质粒带几乎未改变。另外3株耐药水平降低的菌株质粒带无变化。结果表明：大肠杆菌CE01含有与喹诺酮药物抗性有关的质粒，这一质粒被消除剂消除后，CE01菌株的耐药性显著下降，对OFL的MIC由大于50μg/mL变为小于20μg/mL。其它3株经质粒消除剂作用耐药水平降低的菌株可能是细胞膜通透性改变导致耐药。