Eloff J N
Department of Pharmacology, University of Pretoria, South Africa.
Planta Med. 1998 Dec;64(8):711-3. doi: 10.1055/s-2006-957563.
Agar diffusion techniques are used widely to assay plant extracts for antimicrobial activity, but there are problems associated with this technique. A micro-dilution technique was developed using 96-well microplates and tetrazolium salts to indicate bacterial growth. p-Iodonitrotetrazolium violet [0.2 mg/ml] gave better results than tetrazolium red or thiazolyl blue. The method is quick, worked well with Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Escherichia coli and with non-aqueous extracts from many different plants. The method gave reproducible results; required only 10-25 microliters of extract to determine minimal inhibitory concentrations, distinguished between microcidal and microstatic effects, and provided a permanent record of the results. Using S. aureus, and a Combretum molle extract, the technique was 32 times more sensitive than agar diffusion techniques and was not sensitive to culture age of the test organism up to 24 hours. The S. aureus culture could be stored up to 10 days in a cold room with little effect on the assay results. This method was useful in screening plants for antimicrobial activity and for the bioassay-guided isolation of antimicrobial compounds from plants. MIC values determined for sulfisoxazole, norfloxacin, gentamicin, and nitrofuratoin were similar to values indicated in the literature but values obtained with trimethroprim and ampicillin were higher with some bacteria.
琼脂扩散技术被广泛用于检测植物提取物的抗菌活性，但该技术存在一些问题。利用96孔微孔板和四氮唑盐开发了一种微量稀释技术，以指示细菌生长。对碘硝基四氮唑紫[0.2毫克/毫升]比四氮唑红或噻唑蓝给出的结果更好。该方法快速，对金黄色葡萄球菌、粪肠球菌、铜绿假单胞菌和大肠杆菌以及来自许多不同植物的非水提取物效果良好。该方法给出了可重复的结果；测定最低抑菌浓度仅需10 - 25微升提取物，能区分杀菌和抑菌作用，并提供结果的永久记录。使用金黄色葡萄球菌和一种风车子提取物，该技术比琼脂扩散技术敏感32倍，并且对测试生物体长达24小时的培养龄不敏感。金黄色葡萄球菌培养物可在冷藏室保存长达10天，对测定结果影响很小。该方法有助于筛选具有抗菌活性的植物以及对植物中的抗菌化合物进行生物测定指导的分离。测定的磺胺异恶唑、诺氟沙星、庆大霉素和呋喃妥因的最低抑菌浓度值与文献中指出的值相似，但用甲氧苄啶和氨苄西林对某些细菌获得的值较高。
