Relation of Cell Wall to the Virulence of Shigella flexneri

摘要

Most of the work has been devoted to trying to understand why the avirulent mutant of Shigella flexneri 2a (24570), which is antigenically identical to its virulent parent (M-42-43) is nevertheless unable to penetrate the intestinal epithelium. It was found that the strains were different in several characteristics of the cell wall. First, the 24570 was much more resistant to sodium lauryl sulfate, an anionic detergent, than the virulent strain, M4243. It has also been shown that the avirulent strain is four times as electronegative, but this was dependent on the presence of calcium ions. Apparently the electronegativity has made the avirulent strain resistant to other agents such as EDTA and lysozyme. Other studies have shown that the avirulent mutant is deficient in the enzyme, glycerol kinase. This enzyme has shown to be genetically linked to the expression of electronegativity. It was thought that in Shigella, a cell wall mutation may be affecting the expression of glycerol kinase, hence the relation of electronegativity. This was given more credence when it was demonstrated that the uptake of Krebs cycle acids was severely curtailed. Finally, work was begun to indicate that fluorescent probes may be useful to detect differences between virulent and avirulent strains of Shigella.