Studies on the Virulence of a Naturally Occurring Mutant of Salmonella Typhosa

A Chromosomal Locus Which Controls the Ability of Shigella flexneri to Evoke Keratoconjunctivitis

“…Since many of the hybrids which lost their ability to cause a positive Sereney test had also acquired a purine requirement for growth, we were concerned with the possibility that purine dependence could be related to the failure to penetrate cells. Several years ago we and others demonstrated that purine-requiring strains of a variety of bacterial species were avirulent for laboratory models if purine was absent at the site of inoculation, usually the peritoneal cavity (2,3,5,6,9). Reversion to purine independence restored the virulence of these organisms for these models.…”

Invasiveness of Salmonella typhi Strains in HeLa S3 Monolayer Cells

“…The strict adaptation of S. typhi to humans has made it difficult to provide a convenient model of typhoid fever in experimental animals (2,14). Intraperitoneal or intravenous inoculation of S. typhi or S. typhimurium in mice (2,3), with or without gastric mucin, has long been used as an experimental model to estimate the virulence of the typhoid organism and to obtain an insight into the pathogenesis of human typhoid fever. The natural and main route of entrance of S. typhi has been thought to be the intestinal mucosa, and invasion of the organisms into the epithelial cell lining might be essential as the first step for establishing infection.…”

Vi PHAGE-HOST INTERACTION IN SALMONELLA TYPHOSA

“…Sterile solutions of the appropriate carbohydrates were added as needed prior to the pouring of plates. A synthetic medium previously described by Formal et al (1954) was used, with slight modification, in certain experiments.…”

“…Nutrional. Recent experiments by Formal et al (1954) have dealt with a naturally occurring auxotrophic strain of S. typhosa having a nutritional requirement which renders it avirulent for mice. This strain, designated as S. typhosa strain 58 (avirulent), was shown to require a purine in addition to the two amino acids necesary for Inhibition of Vi Figure 3.…”

“…In contrast the LD5o as determined for the original culture is of the order of 2 X 106 cells. The procedures utilized in the determination of the virulence of the cells for mice were essentially those described by Formal et al (1954). 3. Flagellar.…”