Biomechanics of Blood Stream Infections

Summary

Principal Investigator: JOHN YOUNGER
Affiliation: University of Michigan
Country: USA
Abstract: DESCRIPTION (provided by applicant): Intravascular device-related blood stream infection is the leading cause of bacteremia in the United States and is a common and life threatening complication among ill and injured patients. Staphylococcus epidermidis and Klebsiella pneumoniae are common causes of intravascular catheter infection, in part due to their production of biofilms that resist penetration by host innate defenses and antibiotics. Infected devices eject a plume of mediators, bacteria, and bacterial and host matrix that may leave the catheter at nearly half a meter per second and either come to rest in a microvascular debris field in the lung or pass through into the arterial circulation. The fate of this debris- entrapment in a capillary bed or persistence in the blood - is surely linked to the fate of the host, and may be determined by the tendency of these fragments to deform and fracture during their lifespan. The overarching goal of this work is mechanically phenotype this material and to experimentally link these organisms'mechanics to behavior in vivo so as to better understand clinical device infections and their complications. The work is very multidisciplinary and draws on expertise in microrheology, applied mathematics, and established animal models of bacteremia. A major objective is the development of new experimental and computational tools for evaluating microscopic nonlinear viscoelastic particles through collaboration with engineers, mathematicians, and immunologists. Our first aim is to quantify linear and nonlinear viscoelastic properties of biofilm debris and to use advanced image processing and statistical models to evaluate intra- debris heterogeneity. Next, we will consider debris at a population level using mathematical techniques adapted from models of colloid chemistry. Lastly, we will employ animal models of bloodstream infection to validate predictions made from the results of aims 1 and 2 and to test a novel means of promoting bacterial clearance by promoting bacterial aggregation. Equipped with mechanical characterizations of bacterial soft matter at a microscopic scale previously not possible, we hope to answer the following questions: When encountering a capillary, can a biofilm-derived aggregate deform sufficiently to escape filtration? When traveling in the bloodstream, will debris fracture into constituent bacteria or remain as multicellular aggregates? Lastly, how do the fundamental mechanical properties of bacterial aggregates impact host-pathogen interactions in acute life- threatening bloodstream infection and how can those properties be exploited therapeutically? The clinical impact of this work will be to open new therapeutic avenues that address the rheology and mechanics of intravascular infection. Additional benefits include intrinsic value in reframing the problem of bloodstream infection in a biophysical, rather than immunological, context and in developing measurement and computational strategies that extend into a number of other fields interested in the behavior of microscopic viscoelastic material. PUBLIC HEALTH RELEVANCE The goal of this project is to better understand the biophysical properties of small aggregates of bacteria that enter the bloodstream during life threatening infections. Blood infections are common and frequently lethal, especially in immunocompromised patients such as those undergoing treatment for cancer. Our research is being carried out to better understand how patients and bacteria interact and to look for new strategies for protecting and treating patients with serious bloodstream infections.
Funding Period: ----------------2009 - ---------------2013-
more information: NIH RePORT

Top Publications

  1. pmc Klebsiella pneumoniae flocculation dynamics
    D M Bortz
    Department of Applied Mathematics, University of Colorado, Boulder, CO 80309 0526, USA
    Bull Math Biol 70:745-68. 2008
  2. pmc Dynamical system analysis of Staphylococcus epidermidis bloodstream infection
    Hangyul M Chung
    Department of Emergency Medicine and Center for Computational Medicine and Biology, University of Michigan, Ann Arbor, Michigan, USA
    Shock 30:518-26. 2008
  3. pmc Flexible microfluidic device for mechanical property characterization of soft viscoelastic solids such as bacterial biofilms
    Danial N Hohne
    Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
    Langmuir 25:7743-51. 2009
  4. pmc Spatiotemporal dynamics of complement C5a production within bacterial extracellular polymeric substance
    Erin C Conrad
    Department of Emergency Medicine, University of Michigan, Ann Arbor, MI 48109 5303, USA
    J Innate Immun 5:114-23. 2013
  5. pmc Complement c5a generation by staphylococcal biofilms
    Ashley E Satorius
    Department of Emergency Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA
    Shock 39:336-42. 2013
  6. pmc Impact of flow on ligand-mediated bacterial flocculation
    Sarthok Sircar
    Department of Applied Mathematics, University of Colorado, Boulder, CO 80309, United States
    Math Biosci 245:314-21. 2013

Detail Information

Publications6

  1. pmc Klebsiella pneumoniae flocculation dynamics
    D M Bortz
    Department of Applied Mathematics, University of Colorado, Boulder, CO 80309 0526, USA
    Bull Math Biol 70:745-68. 2008
    ..We generate artificial data and illustrate the requirements to accurately identify proliferation, aggregation, and fragmentation of flocs in the experimental domain of interest...
  2. pmc Dynamical system analysis of Staphylococcus epidermidis bloodstream infection
    Hangyul M Chung
    Department of Emergency Medicine and Center for Computational Medicine and Biology, University of Michigan, Ann Arbor, Michigan, USA
    Shock 30:518-26. 2008
    ....
  3. pmc Flexible microfluidic device for mechanical property characterization of soft viscoelastic solids such as bacterial biofilms
    Danial N Hohne
    Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
    Langmuir 25:7743-51. 2009
    ..The flexible microfluidic rheometer addresses the need for mechanical property characterization of soft viscoelastic solids common in fields such as biomaterials, food, and consumer products. It requires only 200 pL of the test specimen...
  4. pmc Spatiotemporal dynamics of complement C5a production within bacterial extracellular polymeric substance
    Erin C Conrad
    Department of Emergency Medicine, University of Michigan, Ann Arbor, MI 48109 5303, USA
    J Innate Immun 5:114-23. 2013
    ....
  5. pmc Complement c5a generation by staphylococcal biofilms
    Ashley E Satorius
    Department of Emergency Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA
    Shock 39:336-42. 2013
    ....
  6. pmc Impact of flow on ligand-mediated bacterial flocculation
    Sarthok Sircar
    Department of Applied Mathematics, University of Colorado, Boulder, CO 80309, United States
    Math Biosci 245:314-21. 2013
    ..Moreover, adhesion is not promoted in a medium with low ionic strength, or flocs with bigger size or higher binder stiffness. The numerical simulations of floc-aggregate number density studies support these findings. ..