Brady M S, Katz S E
Rutgers State University of New Jersey, Cook College, Department of Biochemistry and Microbiology, New Brunswick 08903-0231.
J Assoc Off Anal Chem. 1990 Mar-Apr;73(2):202-5.
Agar nutrient content, cylinder charge volume, thickness (volume) of the agar layer, and incubation temperature were 4 factors varied to determine their effect(s) on the optimization of the cylinder-plate diffusion assay. Chlortetracycline was the pilot antibiotic and Bacillus cereus was used as the assay organism. Zones of inhibition were larger when the incubation temperature was lower than that which was commonly used and/or when the nutrient level was decreased; the zones were smaller when the incubation temperature was raised and/or when an increased nutrient level was used. The thickness (volume) of the assay layer played the most important role; the thinner the layer the less the effect the cylinder charge volume had on the zone diameter. The slopes of the response lines were minimally affected by cylinder charge volume. For a 7 mL assay layer per standard Petri plate, cylinder charge volumes ranging from 150 to 250 microL had little effect on zone diameter. The linearity of the response line was unaffected by assay layer thickness (volume), nutrient level, temperature of incubation, or cylinder charge volume. As long as the conditions for the assay were standardized, there were no discernible effects on recoveries or potencies.
琼脂营养成分、圆筒装样体积、琼脂层厚度（体积）和培养温度是4个可变因素，用于确定它们对圆筒平板扩散试验优化的影响。金霉素是试验抗生素，蜡样芽孢杆菌用作试验微生物。当培养温度低于常用温度和/或营养水平降低时，抑菌圈更大；当培养温度升高和/或使用更高营养水平时，抑菌圈更小。试验层的厚度（体积）起最重要作用；层越薄，圆筒装样体积对抑菌圈直径的影响越小。响应线的斜率受圆筒装样体积的影响最小。对于每个标准培养皿7 mL的试验层，150至250微升的圆筒装样体积对抑菌圈直径影响很小。响应线的线性不受试验层厚度（体积）、营养水平、培养温度或圆筒装样体积的影响。只要试验条件标准化，对回收率或效价就没有明显影响。
