复合指示剂显色法检测细菌最低抑菌浓度的探讨

Compound indicator colorimetric method for detection of bacterial minimal inhibitory concentration

目的:探讨复合指示剂显色法检测细菌最低抑菌浓度(MIC)的准确性。方法:将一定稀释浓度被检细菌悬液加入含有复合指示剂的CAMMH肉汤中,混匀后接种含有不同抗生素系列浓度的特制药敏塑料板(PVC)孔中,滴加液体石蜡隔绝空气,35℃孵育16～24 h,通过观察孔内指示剂颜色变化,判断MIC结果,并与微量肉汤稀释法作比较结果:复合指示剂显色法测定6类抗生素对4株ATCC标准菌株的MIC的符合率为91.0%,±1倍比稀释度的符合率为100%,均在质控范围内;与微量肉汤稀释法相比,复合指示剂显色法测定临床分离的6株革兰氏阳性球菌、16株革兰氏阴性杆菌的MIC符合率分别为98.4%和98.1%;与OXOID公司的药敏纸片比较,符合率为87.5%。结论:复合指示剂显色法能准确快速地检测一般营养要求、快速生长的需氧或兼性厌氧菌的MIC,颜色变化明显,肉眼判读结果容易。

Objective： To determine the accuracy of compound indicator colorimetric method for the detection of bacterial minimal inhibitory concentration （MIC）. Methods： Bacterial suspension diluted at a given concentration was pipetted into the CAMMH broth containing compound indicators and was further incubated in specialized polyvinyl chloride pores coated with antibiotics of various concentrations. This was followed by mounting with liquid paraffin for insulation of ambient air and subsequent incubation at 35℃ for 16 to 24 hours. Colorimetric method was employed for the detection of MIC, based on changes in the color of indicators, for comparison with broth dilution technique. Results： The compound indicator method yielded an overall consistency of 91.0% , and a consistency of 100% in the ＋ 1-fold dilution, for the measurement of MIC of 4 standardized ATCC bacterial strains using 6 types of antibiotics, a result that has met the criteria for quality control. The consistency of MIC of 6 Gram-positive cocci strains and 16 Gram-negative bacilli strains was 98.4% and 98.1% , as compared with broth dilution technique. Both bacterial strains were associated with a consistency of 87. 5% as compared with drug-sensitive slip approach （Oxoid Co）. Conclusion： Compound indicator colorimetrie method may accurately and rapidly detect MIC of aerobic or facultative anaerobic bacteria that are featured by rapid multiplication and modest nutrition requirement. This approach is readily applied as a surrogate of broth dilution technique in clinical practice owing to the marked changes in the color of indicators.