Severe pneumonia due to Parachlamydia acanthamoebae following intranasal inoculation: a mice model.
Parachlamydia acanthamoebae is an obligate intracellular bacterium naturally infecting free-living amoebae. The role of this bacterium as an agent of pneumonia is suggested by sero-epidemiological studies and molecular surveys. Furthermore, P. acanthamoebae may escape macrophages microbicidal effectors. Recently, we demonstrated that intratracheal inoculation of P. acanthamoebae induced pneumonia in 100% of infected mice. However, the intratracheal route of infection is not the natural way of infection and we therefore developed an intranasal murine model. Mice inoculated with P. acanthamoebae by intranasal inoculation lost 18% of their weight up to 8 days post-inoculation. All mice presented histological signs of pneumonia at day 2, 4, 7, and 10 post-inoculation, whereas no control mice harboured signs of pneumonia. A 5-fold increase in bacterial load was observed from day 0 to day 4 post-inoculation. Lungs of inoculated mice were positive by Parachlamydia-specific immunohistochemistry 4 days post-inoculation, and P. acanthamoebae were localized within macrophages. Thus, we demonstrated that P. acanthamoebae induce a severe pneumonia in mice. This animal model (i) further supports the role of P. acanthamoebae as an agent of pneumonia, confirming the third Koch postulate, and (ii) identified alveolar macrophages as one of the initial cells where P. acanthamoebae is localized following infection.
Centre for Research on Intracellular Bacteria (CRIB), Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland.
Ludovic
L
Pilloux
Centre for Research on Intracellular Bacteria (CRIB), Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland.
Nicola
N
Casson
Institute of Medical Microbiology, Medical School Hannover (MHH), Hannover, Germany.
Kirsten
K
Sommer
Institute of Medical Microbiology, Medical School Hannover (MHH), Hannover, Germany.
Andreas
A
Klos
Mouse Pathology Facility, Department of Biochemistry, University of Lausanne, Lausanne, Switzerland.
Jean-Christophe
JC
Stehle
Department of Pathology, Geneva University Hospital, Geneva, Switzerland.
Marc
M
Pusztaszeri
Centre for Research on Intracellular Bacteria (CRIB), Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland. Electronic address: gilbert.greub@chuv.ch.
Gilbert
G
Greub
D000281:Administration, Intranasal; D000818:Animals; D058491:Bacterial Load; D002695:Chlamydiales / Q000276:immunology / Q000472:pathogenicity*; D004195:Disease Models, Animal; D008168:Lung / Q000382:microbiology* / Q000473:pathology; D008264:Macrophages / Q000276:immunology; D051379:Mice; D018410:Pneumonia, Bacterial / Q000276:immunology / Q000382:microbiology* / Q000473:pathology*
Animal model; Intracellular bacteria; Parachlamydiaceae; Pneumonia