Computational Model Aids Biofilm Detection

University of Notre Dame, Notre Dame, IN

http://news.nd.edu/news/56829

An applied mathematician and an environmental biotechnologist at the University of Notre Dame have teamed up to develop a new computational model that simulates the mechanical behavior of biofilms. Their model, they say, may lead to new strategies for studying a range of issues from blood clots to biofilms. (See Figure 1)

Fig. 1 – Staphylococcus aureus biofilm on an indwelling catheter. (Credit: CDC/Rodney M. Donlan, PhD)

Their computational model can be adapted to study clot formation in blood vessels, which can pose the risk of detaching and migrating to the lungs. Clots in healthy people usually stop growing and dissolve on their own. The clots, which result from genetic deficiencies, injury, inflammation, or such diseases as cancer and diabetes, can grow uncontrollably or develop irregular shapes, threatening to detach under the pressure of blood flowing through the vessels. (See Figure 2)

Biofilms, which are found on moist surfaces including veins, water pipes, ship hulls, contact lenses, and hospital equipment, are aggregates of bacterial cells embedded in self-produced extracellular polymer substances (EPS). Biofilms are of particular concern in human infections, as bacteria in biofilms are much more resistant to antibiotics.

Fig. 2 – Red blood cells are enmeshed in a fibrinous matrix on an indwelling vascular catheter. (Credit: CDC/ Janice Carr)

Since biofilms are often found in flowing systems, it is important to understand the effect of fluid flow on biofilms. Biofilms behave like viscoelastic materials. They first stretch elastically, then continue stretching and eventually break, like gum. Most biofilm modeling systems were not able to capture this behavior or predict biofilm detachment. This new model, however, allows for the simulation of this complex behavior. Simulations show that lower-viscosity biofilms are more likely to stretch and form streamers that can detach and clog nearby structures.

Because of that ability, the new model can be used to devise new strategies to better manage biofilms. For example, it can be used to prevent biofouling layers on membrane filtration systems, or to develop methods to clean catheters or surgical equipment.