黏杆菌素对两种诱导多重耐药革兰氏阴性杆菌的体外抗菌活性

Activity of colistin against two induced multidrug-resistant Gram-negative bacteria in vitro

为评价黏杆菌素对兽医临床常见的多重耐药铜绿假单胞杆菌和大肠杆菌的抗菌作用,以微量肉汤稀释法对2种诱导多重耐药菌株进行最低抑菌浓度和最小杀菌浓度测定;采用菌落计数法绘制黏杆菌素对2种诱导多重耐药菌株的时间-杀菌曲线。结果表明,黏杆菌素对铜绿假单胞杆菌和大肠杆菌的最低抑菌浓度分别为2和0.25μg/mL,最小杀菌浓度分别为2和0.5μg/mL。黏杆菌素在0.5、2、4、8、16倍最低抑菌浓度下,对多重耐药大肠杆菌不同时间点的杀菌速率差异显著(P<0.05),呈现浓度依赖性;对铜绿假单胞杆菌呈现部分浓度依赖性。黏杆菌素在2倍最低抑菌浓度下,多重耐药大肠杆菌和铜绿假单胞杆菌菌量在2h内显著下降,在4倍最低抑菌浓度下可在8h内将大肠杆菌全部杀死,在4h内将铜绿假单胞杆菌全部杀死。说明黏杆菌素对诱导多重耐药铜绿假单胞杆菌和大肠杆菌具有强效、速效的杀菌作用。

To evaluate the antibacterial activity of colistin on the multidrug-resistant Pseudomonas aeruginosa and Escherichia coli strains occurred frequently in veterinary clinic,minimal inhibitory concentration（MIC） and minimum bactericidal concentration（MBC） to the two induced multidrug-resistant strains were determined by broth microdilution method. Time-kill curves were prepared according to colony count. Results showed the MIC value of colistin to E.coli and P.aeruginosa was 0.25 and 2μg/mL,and the MBC value was 0.5 and 2μg/mL,respectively.At the concentration of 0.5×,2×,4×,8× and 16×MIC,the antibacterial activity of colistin concentration showed concentration dependent to E.coli,and partly concentration-dependent to P.aeruginosa.At the concentration of 2×MIC,the concentration of E.coli and P.aeruginosa of multidrug resistant strains decreased significantly in 2h. At the concentration of 4×MIC,all of the bacteria can be killed within 8h（E.coli）,4h（P.aeruginosa）. Results indicated that colistin exerted strong and prompt bactericidal effect on the multidrug-resistant P.aeruginosa and E.coli strains.