title: Role of lung epithelial cells in defense against Klebsiella pneumoniae pneumonia.
abstract: The airway epithelium represents a primary site for the entry of pathogenic bacteria into the lungs. It has been suggested for many respiratory pathogens, including Klebsiella pneumoniae, that adhesion and invasion of the lung epithelial cells is an early stage of the pneumonia process. We observed that poorly encapsulated K. pneumoniae clinical isolates and an isogenic unencapsulated mutant invaded lung epithelial cells more efficiently than highly encapsulated strains independent of the K type. By contrast, the unencapsulated mutant was completely avirulent in a mouse model of pneumonia, unlike the wild-type strain, which produced pneumonia and systemic infection. Furthermore, the unencapsulated mutant bound more epithelially produced complement component C3 than the wild-type strain. Our results show that lung epithelial cells play a key role as a host defense mechanism against K. pneumoniae pneumonia, using two different strategies: (i) ingestion and control of the microorganisms and (ii) opsonization of the microorganisms. Capsular polysaccharide avoids both mechanisms and enhances the virulence of K. pneumoniae.
authors.affiliation: Unidad de Investigación, Hospital Universitario Son Dureta, Area de Microbiología, Departamento de Biologia, Universidad de las Islas Baleares and IMEDEA (CSIC-UIB), Palma de Mallorca, Spain.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Cortés
authors.forename: Dolores
authors.initials: D
authors.lastname: Alvarez
authors.forename: Carles
authors.initials: C
authors.lastname: Saus
authors.forename: Sebastián
authors.initials: S
authors.lastname: Albertí
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000276:immunology; D003176:Complement C3 / Q000378:metabolism; D004847:Epithelial Cells / Q000276:immunology*; D006801:Humans; D007710:Klebsiella Infections / Q000209:etiology* / Q000276:immunology; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000472:pathogenicity; D008168:Lung / Q000276:immunology*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010587:Phagocytosis; D018410:Pneumonia, Bacterial / Q000209:etiology* / Q000276:immunology; D011485:Protein Binding; D020545:Respiratory Mucosa / Q000276:immunology*
chemical_list: D003176:Complement C3