engleski

The virulence of Legionella longbeachae in comparison to other Legionella species

Background: Legionella species are one of the most common etiological agents of bacterial pneumonia.There are 48 species and 70 distinct serogroups in the genus of Legionella from which 20 have been associated with human disease. In our previous experiments we determined the LD90 for L. longbeachae. In this study we decided to test and compare the virulence of L. longbeachae serogroup 1 with other Legionella species. Methods: A/J mice were infected by intratracheal inoculation with different Legionella species (L. longbeachae serogroup 1, L. longbeachae serogroup 2, L. pneumophila, L. micdadei and L. steigerwaltii) using a dose of 105 CFU. The infected animals were followed for mortality rate up to 2 weeks. The CFU of bacteria in the lungs of A/J mice were determined 2, 24, 48 and 72 hours post infection. Results: The intratracheal inoculation of 105 CFU L.longbeachae serogroup 1 caused death in 90% of the infected animals within six days, while A/J mice infected with other Legionella species all survived infection.. During the first 72 hours L. longbeachae serogrup 1 rapidly multiplicated in the lungs of intratracheally infected mice, while the number of L. pneumophila and L. micdadei did not change. L. longbeachae serogroup 2, and L. steigerwaltii were promptly eliminated from the lungs of infected mice. Conclusion: Our results show a strong difference in the virulence among Legionella species used in our study. L. longbeachae serogroup 1 is the most virulent species in the used animal model.

Legionella spp.; animal model

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