924. A novel mechanism that contributes to the virulence of an emerging hypervirulent (hypermucoviscous) variant of Klebsiella pneumoniae
Session: Poster Abstract Session: Bacterial Pathogenesis
Saturday, October 22, 2011
Room: Poster Hall B1
Background: A new hypervirulent (hypermucoviscous) clinical variant of Klebsiella pneumoniae (hvKP) has emerged over the last decade. Our goal is to identify new mechanisms, which increase the virulence of hvKP compared to “classic” K. pneumoniae (cKP).

Methods: Ex vivo assays were performed in human ascites, human serum, and in laboratory medium with the hvKP strain hvKP1 (wt) and randomly chosen blood isolates of cKP strains (cKP1-4). An in vivo mouse model that mimics infection due to hvKP was also used. 

Results: A molecule(s)/factor(s) secreted by hvKP1 significantly enhances its growth and/or survival in human ascites and serum ex vivo and in an in vivo mouse model that measures metastatic spread after subcutaneous challenge. Although features such as a size of <3kD, heat stability, and growth characteristics in ascites suggested this molecule(s) was a quorum-sensing compound, it appears that this molecule(s)/factor(s) is involved in iron uptake and is likely a siderophore(s) or another iron-acquisition molecule. Although it is known that iron acquisition it critical for virulence, a novel aspect of this observation is that hvKP1 either produces quantitatively more or produces biologically more active (due to either a modification or being unique) iron-acquisition molecule(s)/factor(s) than those produced by cKP strains.

Conclusion: The data presented delineates a new mechanism by which hvKP increases its pathogenic potential compared to cKP strains. This paradigm may be broadly applicable to other extraintestinal gram-negative bacilli.

Subject Category: B. Bacterial pathogenesis, studies in animal models, molecular pathogenicity

Thomas Russo, MD, CM, FIDSA1,2, Janet Beanan, B. Sc.1, Ruth Olson, B. Sc.1, Ulrike MacDonald, B. Sc.1, Alexander Pomakov3 and Mark Paul Visitacion, MD2,4, (1)Medicine, University at Buffalo-SUNY, Buffalo, NY, (2)Medicine, Western New York Veterans Administration Healthcare System, Buffalo, NY, (3)University at Buffalo-SUNY, Buffalo, NY, (4)Medicine, University at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, NY


T. Russo, None

J. Beanan, None

R. Olson, None

U. MacDonald, None

A. Pomakov, None

M. P. Visitacion, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.