engleski

The susceptibility of C57Bl/6 mice strain to Legionella longbeachae infection

Legionella longbeachae was first described as a cause of pneumonia in 1981. This bacteria is an uncommon pathogen in most parts of the world but causes up to half cases of legionellosis in many regions in Australia. In contrast to other Legionella, this bacteria has been detected only occasionally in water. More commonly, it has been isolated from soil and decomposing materials. Since previous studies indicate the genetically driven permisivity of mice strains for L. pneumophila, in this study we decided to examine the pathogenic potential of L. longbeachae in C57Bl/6 mice. C57Bl/6 mice were infected by intratracheal inoculation of L. longbeachae using two different doses 1000 and 100000 CFU. In the infected animals we followed the mortality assay, bacterial clearance from lung tissue, dissemination of bacteria into other organs and histopathological changes in the lungs. The intratracheal inoculation of 100000 L. longbeachae caused death in 90% of the animals within six days.The LD50 dose of L. longbeachae was determined at 10000 CFU. The animals that received 1000 bacteria survived 21 days post inoculation and were not monitored thereafter. During that period the multiplication of bacteria in the lungs reached a peak at 72 hours after inoculation (1000000-100000000 CFU/lung) and thereafter decreased gradually to the detection level on day seven. Bacteria disseminated already 24 hours after inoculation and we recovered them from the liver and spleen, but in a much lower number than in the lung tissues. Histological appearance of the lungs taken from infected animals was constraint with bronchoalveolar pneumonia. Our results indicate that the C57Bl/6 mice strain is susceptible to infection with L. longbeachae. The LD90 and particulary LD50 dose was unusually low indicating a high infectivity potential of L. longbeachae. Histopathological changes in the lung tissue, indicate on a bronchopneumonia.

Legionella longbeachae; infection

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