engleski

Rapid progression of Legionella longbeachae lung infection in the liver and spleen

Background: Until now few virulence studies have been undertaken with L. longbeachae and little is known about pathogenesis of the disease.Therefore, we established a mice model of experimental legionellosis. It was shown that mice intratracheally inoculated with 105 CFU L. longbeachae developed an acute disease and died within 7 days. Pathohistological changes in the lungs of infected animals were typical for multifocal bronchopneumonia. It was belived that Legionnaires disease is exclusively a lung disease and limited informations were available concerning the progression of the disease. To explore whether a systematisation of the primary process in the lungs may occur we analysed the intensity of bacterial multiplication and pathohistological changes in liver and spleen. Materials and Methods: Pathogen-free female 6- to 10-weeks-old A/J mice were infected by intratracheal inoculation with L. longbeache serogroup 1 using a dose of 105 CFU. We determined the CFU of bacteria in the lung, liver and spleen of A/J mice 2, 24, 48 and 72 hours post infection. We also followed the patohistological changes in these organs 72 hours post infection. Results: 24 hours post infection we isolated L. longbeachae at a CFU concentration around the detection limit of the assay (100 CFU/organ). Increasing multiplication of L. longbeachae in the lung was associated with increased colony counts in analysed organs reaching the concentration between 104 CFU (spleen) and 105 CFU (liver) at 72 hours post infection. Pathohistology of liver and spleen analysed 72 hours post infection showed degenerative and infiltrative changes. In the liver, degeneration of the hepatocytes and focal infiltrations within portal triads by mononuclear and polymorphonuclear leukocytes was observed. The architecture of the spleen showed all signs of severe splenitis. Conclusion: We confirmed that L. longbeachae rapidly disseminate in the liver and spleen causing severe systemic disease in mice.

legionelosis; mice model; systemic disease

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