Johnson J L, Doyle M P, Cassens R G, Schoeni J L
Food Research Institute, University of Wisconsin-Madison 53706.
Appl Environ Microbiol. 1988 Feb;54(2):497-501. doi: 10.1128/aem.54.2.497-501.1988.
Muscle, organ, and lymphoid tissues of four Holstein cows experimentally inoculated (intravenously) with Listeria monocytogenes were examined 2, 6, or 54 days postinoculation for the presence of the organism by direct plating and cold enrichment procedures. L. monocytogenes was isolated from 66% of the tissues sampled; 38% of the isolations were attributed to the use of cold enrichment. Isolation of the organism from muscle tissue was possible only with animals inoculated 2 days before slaughter. The fate of L. monocytogenes during the manufacture and storage of fermented hard salami made from this meat also was determined. Three sausage treatments were evaluated: (i) uninoculated control sausage, (ii) "naturally" contaminated sausage (NC) made from meat of an experimentally inoculated cow, and (iii) sausage made from beef inoculated with a laboratory culture of L. monocytogenes (I). Initial Listeria levels in NC and I sausage were 10(3) CFU/g in trial 1 and 10(4) CFU/g in trial 2. Numbers of L. monocytogenes decreased by approximately 1 log10 CFU/g during fermentation and decreased further during drying and refrigerated storage. Small numbers (less than or equal to 20 CFU/g) of L. monocytogenes were present in I and NC sausage at the end of 12 weeks of refrigerated storage; recovery of these organisms generally depended on the use of an enrichment procedure. The results indicate that L. monocytogenes does not multiply during the fermentation and drying processes typical of hard salami manufacture but that survival may occur if the organism is initially present at greater than or equal to 10(3) CFU/g.
对4头经静脉注射单核细胞增生李斯特菌进行实验接种的荷斯坦奶牛的肌肉、器官和淋巴组织，在接种后2天、6天或54天，通过直接平板接种和冷增菌程序检查该菌的存在情况。从66%的采样组织中分离出了单核细胞增生李斯特菌；38%的分离培养归因于使用了冷增菌法。仅在屠宰前2天接种的动物的肌肉组织中才可能分离出该菌。还确定了单核细胞增生李斯特菌在由这种肉制成的发酵硬香肠的制作和储存过程中的命运。评估了三种香肠处理方式：(i)未接种的对照香肠，(ii)由实验接种奶牛的肉制成的“自然”污染香肠(NC)，以及(iii)接种了单核细胞增生李斯特菌实验室培养物的牛肉制成的香肠(I)。在试验1中，NC和I香肠中的初始李斯特菌水平为10³CFU/g，在试验2中为10⁴CFU/g。在发酵过程中，单核细胞增生李斯特菌的数量减少了约1个对数CFU/g，在干燥和冷藏储存过程中进一步减少。在冷藏储存12周结束时，I和NC香肠中存在少量(≤20 CFU/g)的单核细胞增生李斯特菌；这些菌的回收通常依赖于增菌程序。结果表明，在硬香肠制作典型的发酵和干燥过程中，单核细胞增生李斯特菌不会繁殖，但如果该菌最初存在量≥10³CFU/g，则可能存活。
