Takai S, Sugawara T, Watanabe Y, Sasaki Y, Tsubaki S, Sekizaki T
Department of Animal Hygiene, School of Veterinary Medicine and Animal Sciences, Kitasato University, Aomori, Japan.
Vet Microbiol. 1994 Mar;39(1-2):187-92. doi: 10.1016/0378-1135(94)90099-x.
Repeated passage of virulent Rhodococcus equi ATCC 33701 and L1 at 38 degrees C resulted in attenuation of the strains as a result of curing the virulence plasmid; at 30 degrees C, repeated passage had no such effect. At a temperature of 38 degrees C the plasmid-bearing cells replicated more slowly than their plasmid-cured derivatives and so were gradually replaced by cells lacking plasmids. In contrast, at a temperature of 30 degrees C the growth rate of either strain was not affected by the presence or absence of the plasmid. No plasmid-cured derivative was recovered from mouse organs at 48 h after inoculation of a mixture of equal numbers of bacteria with and without plasmids. It is concluded that under nonselective conditions growth temperature is an important factor in maintaining the virulence of R. equi.
在38℃下对强毒马红球菌ATCC 33701和L1进行反复传代培养，由于毒力质粒的消除，导致菌株毒力减弱；而在30℃下反复传代则没有这种效果。在38℃时，携带质粒的细胞复制速度比其质粒消除后的衍生物慢，因此逐渐被缺乏质粒的细胞所取代。相比之下，在30℃时，任一菌株的生长速度不受质粒存在与否的影响。在接种等量有质粒和无质粒细菌的混合物48小时后，从小鼠器官中未回收质粒消除后的衍生物。得出的结论是，在非选择性条件下，生长温度是维持马红球菌毒力的一个重要因素。
