Gamaleya Research Institute of Epidemiology and Microbiology, Moscow, Russia
As the result of testing three different variants, the experimental models of persisting infection for P.aeruginosa and B.cepacia have been developed. These doses differ in the time of administration, doses of antibiotics and the infective doses of the microorganisms. The administration of the subinhibiting concentration of antibiotics for 5 days and the subsequent infection of laboratory animals (non-nbred mice) B.ñepacia strains in a dose of LD50 leads to a considerable increase in the survival rate of mice and to a longer period (up tî 20 days) of obtaining inoculative material from the spleen. The isolated cultures are characterized by a sharply slower growth on artificial culture media (up to 5-7 days as compared with 24-48 hours for the initial culture). The newly developed models have made it possible to control different stages of the infectious process in the induced increase or decrease of the virulent properties of the infective agent and in changes in the immune status of the host. As the result of these studies, in some mice (10%) infected with B.cepacia after the injection of γ-hydroxybutyric acid lactone the infection has taken the acute form, while in the mice infected with P.aeruginosa no such effect has been observed. On the contrary, in the mice infected with P.aeruginosa and then receiving cyclophosphamide the transition of the infection into the acute form has been observed in 30% of the animals. In the mice infected with B.cepacia no such effect has been noted after the injection of this preparation. Different effects produced by cyclophosphamide and lactone are discussed from the positions of “quorum sensing” in pathogenic bacteria.
Zh. Mikrobiol. (Moscow), 2004, No. 2. P. 14—20