Humphrey T J
Food Unit, Public Health Laboratory, Exeter, Devon, England, UK.
Int J Food Microbiol. 1994 Jan;21(1-2):31-40. doi: 10.1016/0168-1605(94)90197-x.
Salmonella enteritidis can contaminate the contents of clean, intact shell eggs as a result of infections of the reproductive tissue of laying hens. The principal site of infection would appear to be the upper oviduct. In egg contents the most important sites of contamination are either the outside of the vitelline membrane or the albumen surrounding it. In fresh eggs, only few salmonellas are present and as albumen is an iron-restricted environment, growth will only occur once storage-related changes to vitelline membrane permeability, which allow salmonellas to invade yolk contents, have taken place. When this happens high populations are achieved in both yolk contents and albumen. Some eggs from naturally infected hens have been found to contain large numbers of S. enteritidis. The rate of change in membrane permeability is temperature-dependent. In eggs stored at 20 degrees C, yolk invasion is uncommon until eggs have been stored for 3 weeks. In stimulated kitchen conditions where temperatures reached 30 degrees C, salmonellas could grow rapidly after a few days.
肠炎沙门氏菌可因蛋鸡生殖组织感染而污染清洁、完好的带壳蛋内容物。主要感染部位似乎是输卵管上部。在蛋的内容物中，最重要的污染部位要么是卵黄膜外部，要么是其周围的蛋清。在新鲜鸡蛋中，沙门氏菌数量很少，而且由于蛋清是铁限制环境，只有在与储存相关的卵黄膜通透性发生变化，使沙门氏菌能够侵入蛋黄内容物后，才会生长。当这种情况发生时，蛋黄内容物和蛋清中都会有大量细菌。已发现一些来自自然感染母鸡的鸡蛋含有大量肠炎沙门氏菌。膜通透性的变化速率取决于温度。在20摄氏度储存的鸡蛋中，在储存3周之前，卵黄被入侵的情况并不常见。在模拟厨房条件下，温度达到30摄氏度时，沙门氏菌在几天后就能迅速生长。
