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Infection and Immunity, September 2001, p. 5294-5304, Vol. 69, No. 9
Centre de Recherche en Infectiologie,
Université Laval, Québec, Québec, Canada
Received 3 May 2001/Returned for modification 5 June 2001/Accepted 18 June 2001
Mortality related to bacteremic pneumonia remains high, and the
role of sepsis in inflammation, pulmonary injury, and death remains
unclear, mostly in leukopenic states. In the present study, the
microbiology, histopathology, and host response to Streptococcus pneumoniae and Klebsiella pneumoniae infection were
determined in an experimental model of bacteremia in immunocompetent
and leukopenic mice. Leukocyte depletion by cyclophosphamide did not impair the early clearance of pneumococci from blood but facilitated growth in lungs. By contrast, klebsiellae rapidly grew in blood of
leukopenic mice. These observations suggest that tissue-based phagocytes and circulating leukocytes, respectively, play prominent roles in S. pneumoniae and K. pneumoniae
eradication. The kinetics of leukocyte recruitment in lungs during
S. pneumoniae bacteremia suggested early strong
inflammation in immunocompetent mice that is associated with tumor
necrosis factor alpha release and histological disorders, including
cell debris and surfactant in alveolar spaces. Leukocyte depletion
further stimulated pulmonary capillary leakage both in S. pneumoniae and K. pneumoniae bacteremia, which seemed attributable to bacterial virulence factors. Nitric oxide production did not differ significantly among groups. Leukopenia and low platelet
counts characterized the late stage of bacteremia for both strains, but
only K. pneumoniae altered renal function. Understanding the pathogenesis of bacteremia will help establish beneficial therapies
for both sepsis and pneumonia.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.9.5294-5304.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Pulmonary and Systemic Host Response to Streptococcus
pneumoniae and Klebsiella pneumoniae Bacteremia in
Normal and Immunosuppressed Mice
*
Corresponding author. Mailing address: Centre de
Recherche en Infectiologie, Centre Hospitalier de l'Université
Laval, 2705 Boul. Laurier, Sainte-Foy, Québec, Canada G1V 4G2.
Phone: (418) 654-2705. Fax: (418) 654-2715. E-mail:
Michel.G.Bergeron{at}crchul.ulaval.ca.
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