Wenzel J M, Marth E H
Department of Food Science, University of Wisconsin-Madison 53706.
J Dairy Sci. 1990 Dec;73(12):3357-65. doi: 10.3168/jds.S0022-0302(90)79031-5.
Behavior of Listeria monocytogenes in a commercial starter culture medium with internal pH control was examined. The IPCM-1 medium was inoculated with L. monocytogenes (strain V7, Scott A, or California) at ca. 10(3) cfu/ml and Streptococcus cremoris (.25%, 1.6 x 10(5) or 1.0%, 8.6 x 10(5) cfu/ml) and was incubated at 21 or 30 degrees C for 30 h. The pH of the uninoculated medium and control (L. monocytogenes only) was between 6.8 and 7.0 before and after incubation. The area on a figure between control and treatment curves for numbers of L. monocytogenes was calculated, designated as area of inhibition, and used to quantitate inhibition of L. monocytogenes caused by S. cremoris. No significant difference was found in area of inhibition or pH values at 6, 24, and 30 h of incubation among the three strains of L. monocytogenes for a given set of conditions (percentage of S. cremoris added and temperature). Inhibition of the pathogen increased with an increase in amount of S. cremoris inoculum used and with higher rather than lower incubation temperature. Populations of L. monocytogenes in IPCM-1 medium without S. cremoris after 30 h of incubation were 10(6) to 10(7)/ml at 21 degrees C and 10(8)/ml at 30 degrees C. At 21 degrees C inhibition of Listeria began after 18 and 24 h and at 30 degrees C after 12 and 15 h of incubation in samples inoculated with 1.0 and .25% S. cremoris, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
研究了在具有内部pH值控制的商业发酵剂培养基中，单核细胞增生李斯特菌的行为。将单核细胞增生李斯特菌（菌株V7、斯科特A或加利福尼亚）以约10³ cfu/ml的浓度接种到IPCM - 1培养基中，并接种了嗜热链球菌（0.25%，1.6×10⁵或1.0%，8.6×10⁵ cfu/ml），然后在21或30℃下孵育30小时。未接种培养基和对照（仅单核细胞增生李斯特菌）的pH值在孵育前后均在6.8至7.0之间。计算单核细胞增生李斯特菌数量的对照曲线和处理曲线之间的图形面积，称为抑制面积，并用于定量嗜热链球菌对单核细胞增生李斯特菌的抑制作用。在给定的一组条件（添加嗜热链球菌的百分比和温度）下，三种单核细胞增生李斯特菌菌株在孵育6、24和30小时时，抑制面积或pH值均未发现显著差异。病原体的抑制作用随着嗜热链球菌接种量的增加以及孵育温度升高而增强，而非降低。在不含嗜热链球菌的IPCM - 1培养基中，孵育30小时后，单核细胞增生李斯特菌在21℃下的数量为10⁶至10⁷/ml，在30℃下为10⁸/ml。在接种了1.0%和0.25%嗜热链球菌的样品中，分别在21℃下孵育18和24小时后以及在30℃下孵育12和15小时后开始出现对李斯特菌的抑制作用。（摘要截短至250字）
