MedicalResearch.com with [caption id="attachment_27455" align="alignleft" width="125"] Dr. Tara Moriarty Ph.D.[/caption] Senior Author: Tara Moriarty, Ph.D. University of Toronto, Canada Faculty of Dentistry, Matrix Dynamics Group Faculty of Medicine, Department of Laboratory Medicine and Pathobiology [caption id="attachment_27454" align="alignleft" width="125"] Rhodaba Ebady, Ph.D. student[/caption] Lead Author: Rhodaba Ebady, Ph.D. student University of Toronto, Canada Faculty of Dentistry, Matrix Dynamics Group MedicalResearch.com: What is the background for this study? What are the main findings? Response: The spread of microbes via the bloodstream (dissemination) is responsible for most of the mortality associated with bacterial infection. Even though this is a clinically important step of many infectious diseases, and likely an important target for disease treatment, we don’t know how most microbes disseminate. One of the key steps in this process is adhesion of bacteria to the inner surfaces of blood vessels. This allows bacteria to slow down enough to grab onto vessel surfaces, then escape from the blood stream into tissues where it’s easier for them to live. It’s a bit like the problem faced by a person being carried down a fast-flowing river who needs to grab onto something on the banks to get out onto dry land. A big problem for bacteria, and any other cells which must stick to blood vessel walls (like white blood cells travelling to a site of infection or inflammation), is that they have to be able to stick to vessel walls without being ripped off by the flow of blood. They have to have adhesion mechanisms strong enough to overcome forces due to flow. It’s also really helpful to be able to hang on but keep moving along walls until they reach a good spot to get out. This is important for white blood cells too, which have to “sample” their environment to get to the right place to get out of blood flow. Even though the problem of how bacteria stick to blood vessel walls is so important clinically, the mechanisms bacteria use to do this are not widely understood. Part of this gap in our knowledge arises because we haven’t had good tools to study this process as it happens, and to understand how force affects bacterial interaction with vessel walls. The process of bacteria sticking to blood vessel walls is very fast, and hard to observe. The methods to observe this have already been developed, but the major technical innovations of our paper were to figure out how to identify and track the movement of the individual bacteria which stuck to vessel walls among millions flowing past, and to figure out how to set up a flow chamber system which replicated certain conditions in human blood vessels. Figuring out how to do this allowed us to figure out a lot about how the bacteria moved, and the forces and mechanisms involved in adhesion. It took a couple of years just to figure out the common patterns in the thousands of tracks of bacteria interacting with blood vessels, after the initial technical innovation.