动态分析抗菌作用的新方法

A novel method for the dynamic analysis of antimicrobial effect

最低抑菌浓度(MIC)是表征抗菌药物对细菌生长抑制最终效应的常规方法,不能描述抑菌作用的时间过程,药敏试验也不适用于高抗药性水平菌株的治疗方案确定.因此本文提出了一个普适性的新药敏试验方法.不同接种量的质控菌株Escherichia coli ATCC 25922和临床高抗药性水平菌株E.coli BBZ在不同系列浓度的6种抗菌药物(环丙沙星、氨苄西林、头孢噻呋、阿米卡星、硫酸黏菌素和多西环素)作用下,37℃下培养1200 min,连续检测时间序列点的光密度值A600作为反应变量,以相对抑菌效应(RIE=((a.b)/a)×100%)表征抑制效应,进而用等效线图表征药物浓度和时间协同抑制效应的动态过程,量化了浓度依赖型和时间依赖型,细化不同菌株对药物敏感性的差别.由此得到,达到最大抑制效应时,需要的最低药物浓度和时间,以及增大药物浓度或延长反应时间对抑制效应的影响,这正是临床用药最需要的信息.此外,大接种量下最大抑菌效应很低,表明不适合治疗.本方法为防治高抗药性菌株感染提供了药敏试验方法,也有益于促进新药研发药敏检测方法的改进.最后提出适于临床应用的、快速定性显示药物敏感性的方法的建议.

The minimum inhibitory concentration （MIC） method is conventionally used to characterize the final inhibitory effect of antimicrobial agents on bacterial growth. However, this method cannot describe the process ofbacteriostasis, whereas the antibiotic susceptibility test （AST） is not suitable for high resistant strains. Therefore, a general AST method is proposed herein： different inoculum sizes of the quality-control strain E. coli ATCC 25922 or high resistant clinical strain E. coli BBZ were exposed to a series of concentrations of six different antimicrobial agents （Ciprofloxacin, Ampicillin, Ceftiofur, Amikacin, Colistin sulphate, and Doxycycline） at 37~C for 1200rain. A600, a response variable, was detected at the ＂at regular intervals of time, and the inhibitory effect was expressed by relative inhibitory efficiency （RIE= [（a-b）/a] x 100%）. Furthermore, the dynamics of synergistic effect of antibiotic concentration and time on the inhibition was characterized by the RIE contour map, which quantifies the concentration-dependent or time-dependent types of inhibition and refines the difference between various resistant strains. Clinically relevant information can be revealed, such as the maximum inhibitory effect, the lowest drug concentration and time required to achieve it, and the changes in inhibitory effect with an increase in drug concentration or reaction time. In addition, the maximum inhibitory effect of a large inoculum size on the bacteriostatic process is low, resulting in ineffective treatment. This synergistic method is suitable for the prevention and control of infections caused by high resistant strains, and is beneficial to promote the AST method for the development of new antibiotics. At last, a rapid qualitative AST method has been proposed for clinical application.