How Do a Few Attached Staphylococcus aureus Bacteria Evade Innate Immunity to Initiate Biofilm Infection on an Implanted Medical Device?

项目总结/文摘

PROJECT SUMMARY/ABSTRACT Implanted medical devices have saved lives and improved the quality of life for many. But such implants remain vulnerable to troublesome infection by microorganisms that aggregate on or near the device in a biofilm. More than three decades of work on antimicrobial coatings and antibiotic therapies have failed to produce robust solutions to biofilm infection, suggesting that researchers have been missing an essential piece of this puzzle. We contend that the key to preventing implant-related infection is a better understanding and orchestration of innate immunity at the earliest stage. In particular, it is hypothesized that slow recruitment of neutrophils to a sparsely contaminated biomaterial gives some bacteria time to grow into aggregates, and that these aggregates are protected from killing by neutrophils and persist. In three Specific Aims, this project will quantify the following phenomena: Aim 1. Neutrophil recruitment times to bacteria-contaminated biomaterial surfaces. Aim 2. Growth dynamics of bacteria attached to an abiotic surface prior to neutrophil discovery. Aim 3. Bacterial and neutrophil fates post neutrophil discovery. These measurements will be made by an interdisciplinary team merging expertise in quantitative biochemical engineering, molecular microbiology, immunology, orthopedic surgery, biomaterials, and mathematics and statistics. The primary model bacterium will be Staphylococcus aureus and the animal models will all be in mice. Four complementary experimental models will be used: 1) in vitro video microscopy of bacteria-human neutrophil interactions on a sparsely inoculated abiotic surface; 2) whole animal imaging of neutrophil and bacterial dynamics following subcutaneous implantation; 3) intravital imaging with single cell resolution of neutrophil- bacteria dynamics on a subcutaneous implant, and 4) a conventional subcutaneous implant model to be used for cytokine/gene profiling, cataloging of immune cell types present, and additional microscopy. This project will generate unique data sets emphasizing quantitative, probabilistic characterization of the host-pathogen interaction in the first several hours after implantation, the likely window for preventing a biofilm infection from establishing. This work will open the door to new strategies for preventing infections on implanted medical devices by boosting neutrophil numbers or speeding up their delivery to the contaminated implant with multiple potential advantages: short-term intervention, broad spectrum applicability, and obviation of antibiotic resistance concerns.