Identification of Klebsiella pneumoniae virulence determinants using an intranasal infection model

Abstract

SummaryKlebsiella pneumoniae is a Gram-negative enterobacterium that has historically been, and currently remains, a significant cause of human disease. It is a frequent cause of urinary tract infections and pneumonia, and subsequent systemic infections can have mortality rates as high as 60%. Despite its clinical significance, few virulence factors of K. pneumoniae have been identified or characterized. In this study we present a mouse model of acute K. pneumoniae respiratory infection using an intranasal inoculation method, and examine the progression of both pulmonary and systemic disease. Wild-type infection recapitulates many aspects of clinical disease, including significant bacterial growth in both the trachea and lungs, an inflammatory immune response characterized by dramatic neutrophil influx, and a steady progression to systemic disease with ensuing mortality. These observations are contrasted with an infection by an isogenic capsule-deficient strain that shows an inability to cause disease in either pulmonary or systemic tissues. The consistency and clinical accuracy of the intranasal mouse model proved to be a useful tool as we conducted a genetic screen to identify novel virulence factors of K. pneumoniae . A total of 4800 independent insertional mutants were evaluated using a signature-tagged mutagenesis protocol. A total of 106 independent mutants failed to be recovered from either the lungs or spleens of infected mice. Small scale independent infections proved to be helpful as a secondary screening method, as opposed to the more traditional competitive index assay. Those mutants showing verified attenuation contained insertions in loci with a variety of putative functions, including a large number of hypothetical open reading frames. Subsequent experiments support the premise that the central mechanism of K. pneumoniae pathogenesis is the production of a polysaccharide-rich cell surface that provides protection from the inflammatory response.

Lipid-Based Signaling Modulates DNA Repair Response and Survival against Klebsiella pneumoniae Infection in Host Cells and in Mice

“…Lawlor and colleagues demonstrated that CPS is a crucial component of the K. pneumoniae surface structure that is relevant to the internalization of this pathogen into epithelial cells (24). In our studies, K. pneumoniae showed significant internalization after 1 hour of infection, indicating that the infection is time-dependent and bacterial load-dependent.…”

“…Previously, isogenic capsule-negative strains (DCPS) showed higher adhesion to airway cells (24). Thus, we studied whether CPS also plays a role in the internalization and its relevance to lipid rafts.…”

Pulmonary infection by Yersinia pestis rapidly establishes a permissive environment for microbial proliferation

“…Similarly, wildtype Klebsiella pneumoniae, which can also cause an acute bacterial pneumonia, failed to significantly trans-complement isogenic strains that have mutations in predominant virulence genes (such as a ΔcpsB mutant, which lacks the polysaccharide capsule) or pCD1 − mutants of Y. pestis (Fig. 3B) (16). Conversely, virulent Y. pestis was able to significantly trans-complement ΔcpsB K. pneumoniae and fully trans-complement pYV − Y. pseudotuberculosis IP2666c (Fig.…”

Antibacterial Activity of Essential Oil from Abies holophylla against Respiratory Tract Bacteria

“…Hospitalized or elderly patients with K. pneumoniae infections are at great risk of dying, with reported mortality rates of between 25% and 60% (Lawlor et al 2005). S. pyogenes is also a known cause of morbidity and mortality in humans and is responsible for both respiratory tract infections and invasive diseases (Musher 1992;Reinert et al 2004).…”