[Effect of the constitutive activity of pathogenicity genes in Listeria monocytogenes].

The effect of the constitutive expression of pathogenicity factors in L. monocytogenes was studied on the model of the intraperitoneal infection of mice. The constitutive expression was due to a single amino acid substitution in the transcriptional factor PfrA, the master regulator of L. monocytogenes virulence genes. The effective lethal dose (LD50) for the strain with the constitutive expression of pathogenicity factors was 3 times lower than for the isogenic wildtype strain. When introduced in equal doses, this Listeria strain led to the death of the animals 1-2 days earlier than the wild-type stain. The study revealed that the constitutive expression of pathogenicity factors resulted in faster dissemination of bacteria in the body of the animal during the first 24 hours, but led to their earlier elimination from the internal organs at later stages of infection.