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Lipopolysaccharide O-antigen promotes persistent murine bacteremia
Joanelle Z Lugo1, Sarah Price, Julia E Miller
1Department of Emergency Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
Shock (Augusta, Ga.)
|January 17, 2007
Summary
The O-antigen of Klebsiella pneumoniae O1:K2 promotes bacterial virulence by helping it evade immune responses and persist in the bloodstream, liver, and spleen, leading to increased lethality during pneumonia and bacteremia.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Bacteremia is a frequent complication of Klebsiella pneumoniae pneumonia.
- Previous studies indicated lipopolysaccharide (LPS) O-antigen contributes to lethality by promoting bacteremia.
Purpose of the Study:
- To investigate the role of O-antigen in Klebsiella pneumoniae O1:K2 virulence during bacteremia.
- To evaluate the impact of O-antigen deficiency on host immune responses and bacterial clearance.
Main Methods:
- In vitro studies using cultured murine alveolar macrophages (MH-S).
- In vivo murine models of bacteremia following intravenous injection.
- Analysis of immune cell activation, cytokine/chemokine secretion, neutrophil killing, bacterial clearance, and survival rates.
- Gene expression profiling of inflammatory mediators.
Main Results:
- O-antigen-deficient Klebsiella pneumoniae activated macrophages more strongly and were more susceptible to neutrophil killing in vitro.
- Absence of O-antigen led to faster bacterial clearance from blood, liver, and spleen, and increased survival in vivo.
- O-antigen-deficient infections showed downregulated cytokine and chemokine expression in liver and spleen by 24 hours postinfection.
Conclusions:
- The O-antigen of K. pneumoniae O1:K2 enhances virulence by reducing macrophage activation and neutrophil killing.
- O-antigen promotes persistent infection in the bloodstream, liver, and spleen, contributing to disease severity.
- Targeting O-antigen may represent a strategy to combat Klebsiella pneumoniae bacteremia.
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