Werner E, Seibold M, Antweiler E
Department of Microbiology, Robert Koch Institute, Berlin, Germany.
Mycoses. 1993 Mar-Apr;36(3-4):125-30. doi: 10.1111/j.1439-0507.1993.tb00699.x.
The role of buffering in the determination of the minimal inhibitory concentration (MIC) of fluconazole was studied with Candida species. Agar dilution tests were performed on media (pH 7.25) buffered with either phosphate or morpholinopropane-sulfonic acid (MOPS) or endomethylene-tetrahydrophthalic acid (EMTA), 0.1 mol l-1 each, or on the unbuffered medium. It consisted of casitone and glucose supplemented with FeCl3 and MgSO4. The MICs recorded after 24 h at 37 degrees C extended from 0.1 mg l-1 to > or = 100 mg l-1 on the phosphate and EMTA medium, being concordant on both media. On the MOPS medium and the unbuffered medium the readings were also concordant; the MICs, however, were mostly 25 mg l-1 or higher. This increase of the values--up to six dilution steps--could not be correlated with the amount of acid secreted by the single strains. EMTA proved to be an alternative to phosphate in this system, and because it allows a faster growth of the yeasts it might be superior to phosphate. The concordance of the MIC values in the presence of such different buffer compounds tends to suggest that they indeed indicate the strongest inhibition attainable in vitro by fluconazole. MOPS was confirmed to be of no use in this system.
采用念珠菌属研究了缓冲作用在氟康唑最低抑菌浓度（MIC）测定中的作用。在分别用0.1 mol/L的磷酸盐、吗啉丙烷磺酸（MOPS）或内亚甲基四氢邻苯二甲酸（EMTA）缓冲的培养基（pH 7.25）上，或在未缓冲的培养基上进行琼脂稀释试验。该培养基由酪蛋白胨和葡萄糖组成，并添加了FeCl3和MgSO4。在37℃孵育24小时后，在磷酸盐和EMTA培养基上记录的MIC范围为0.1 mg/L至≥100 mg/L，两种培养基上的结果一致。在MOPS培养基和未缓冲的培养基上读数也一致；然而，MIC大多为25 mg/L或更高。这种值的增加——高达六个稀释步骤——与单个菌株分泌的酸量无关。在该系统中，EMTA被证明是磷酸盐的替代品，并且由于它能使酵母生长更快，可能优于磷酸盐。在存在如此不同缓冲化合物的情况下，MIC值的一致性倾向于表明它们确实代表了氟康唑在体外可达到的最强抑制作用。证实MOPS在该系统中无用。
