福氏志贺氏菌2a、3a型变异的研究

STUDIES ON VARIATIONS OF SHIGELLA FLEXNERI 2a, 3a

本实验用紫外线诱变福氏志贺氏菌2a、3a型,使其发生了生化突变,耐药性突变和抗原性变异等现象。福氏2a菌对鼠李糖和蕈糖不发酵,经诱变后变为发酵株,对红霉素耐药变为敏感菌株。福氏3a菌株在各种糖培养基中可发生型抗原和群抗原丢失现象。诱变后的福氏2a-A_2菌在伊红美兰培养基上传代连续三次分化出福氏3a型菌。这种突变仅发生在极少数营养缺陷型菌株中。本实验选育出一株福氏3a-A_2 met^-(甲硫氨酸缺陷型)无毒株,免疫家免后的抗体血清效价比原始株高10倍,其免疫保护率为100％,此菌株可用于制作痢疾杆菌活菌苗。

Biotype 2a, 3a of S. Flexneri mutagenized by ultraviolet rays developed variable variations in biochemical, drug-tolerant and antigenic characteristics in this study. We found that biotype 2a of S. Flexneri was antifermentative to rhamnose and trehalose and was drugtolerant to erythromysin. On the contrary, the mutagenic S. flexneri 2a became fermentative to rhamnose and trehalose and sensitive to erythromysin. The mutagenic strain of S. flexneri 2a-A2, subjected to subculture in vitro for three passages on eosin methylene blue agar medium, could be transformed into the strain of S. flexneri 3a, but only a few dystrophic strain could be transformed into it. It was also discovered that the strain of S. flexneri 3a could produce antigenic loss in serotype and serogroup in culture of various sugar media. In addition, one avirulent strain of S. flexneri 3a-A2 met^- (methionine dystrophic) which was selected during the study was inoculated into rabbits,and the titers of the serum antibody against the strain of S. flexneri 3a-A2 met^- were 10 times higher than those of the serum antibody against the primitive strain, and its immunoprotective rate was 100%. Therefore, it was suggested that this selected strain could be used as a live S. dysenteriae vaccine.