氨苄西林和安普霉素对禽源沙门菌的体外联合效果和耐药突变选择窗的研究

Study on the combined effect and the mutant selection window of ampicillin and apramycin against avian Salmonella in vitro

目的探讨氨苄西林(ampicillin,AMP)和安普霉素(apramycin,APR)联合是否能增强对禽源沙门菌的抗菌效果,以及能否缩小甚至关闭AMP对沙门菌的耐药突变选择窗(mutant selection window,MSW)。方法以ATCC 25922为质控菌,对22株禽源沙门菌用棋盘稀释法进行AMP和APR的联合药敏试验,并以部分抑菌浓度指数(fractional inhibitory concentration index,FICI)评价联合效果,挑选其中2株菌用试管法进行杀菌动力学试验并绘制时间-杀菌曲线;挑选6株菌进行不同加药顺序的联合药敏试验;对其中10株用琼脂稀释法进行AMP单药和联合用药的防耐药突变浓度(Mutation Preventive Concentration,MPC)测定,以选择指数(selection index,SI)和MSW范围来评价防突变效果。结果22株菌的联合药敏试验中相加效应占56.52%,协同效应占43.48%;杀菌动力学试验的2株菌在第4小时的联合用药组菌落对数值较最有效的单药组分别减少了3.10和1.94 lgCFU/mL;不同加药顺序试验的配对t检验结果为P>0.05,无显著性差异;MPC的测定试验中,SI值≥1的菌株的MSW范围明显缩小甚至关闭。结论AMP和APR对禽源沙门菌的体外联合效果较好,且能有效缩小AMP对沙门菌的耐药突变选择窗,不同加药顺序对联合用药效果无影响。

Objective To investigate whether the combination of ampicillin(AMP)and apramycin(APR)can enhance the antibacterial effect on avian Salmonella,and whether it can narrow or even close the mutation selection window of AMP for Salmonella resistance mutant selection window(MSW).Methods Using ATCC25922 as the quality control bacteria,the AMP and APR combined drug susceptibility test of 22 avian Salmonella strains were carried out by the chessboard dilution method,and the combined effect was evaluated by the fractional inhibitory concentration index(FICI).Two strains were selected among them for bactericidal kinetics by test tube method and time-kill curve was drawn;6 strains were selected for combined drug sensitivity test with different adding sequence;10 of them were used agar dilution method for AMP single drug and combined drug control the mutation preventive concentration(MPC)was measured,and the Selection Index(SI)and MSW range were used to evaluate the mutation prevention effect.Results In the combined drug sensitivity test of 22 strains,the additive effect accounted for 56.52%,and the synergistic effect accounted for 43.48%.The two bacteria in the bactericidal kinetics test had the most effective colony logarithm of the combined drug group at the 4th hour.Reduced 3.10 and 1.94 lgCFU/mL;the paired t-test results of different adding sequence tests were P>0.05,no significant difference;in the MPC measurement test,the MSW range of the strain with SI value≥1 was significantly reduced or even closed.Conclusion The combined effect of AMP and APR on avian-derived Salmonella in vitro is good,and can effectively reduce the mutation selection window of AMP for resistance to Salmonella.Different dosing orders have no effect on the combination.