Hundreds of thousands of people in the United States, if not more, suffer infections each year from medical devices that have developed microbial films — sticky mats of bacteria that are hard to find and clean off.
But University of Texas researchers say they have figured out why the film develops, a finding that could lead to a way to prevent such mats from forming on catheters, breathing tubes and other medical equipment.
The research, published last week in the Proceedings of the National Academy of Sciences, studied how some kinds of bacteria figure out if they are attached to a surface. It found that the bacteria attach themselves through a phenomenon called shear, which leads bacteria to form the film.
UT science writer Marc Airhart describes the phenomenon thusly:
“Imagine you’re in a river and you’re trying to pull yourself along underwater by grabbing rocks on the bottom and pulling forward. Shear is the force that is stretching your body; it’s what you feel in your arms and legs as you pull against the resistance of the water. You might not feel much shear if the water is still and you’re moving slowly, or it might be high if the river is moving fast and you’re going the opposite way. Let go of the rocks and just ‘go with the flow’ of the river, and you won’t feel any shear.”
Estimates vary on how many people in the United States suffer infections as a result of the biofilm. A 2014 study by the Centers for Disease Control and Prevention estimated 185,000, while a study in the Clinical Infectious Diseases Journal put the number at 2.8 million.
Previous research had shown that the bacteria start forming the film when they sense that they are attached. What was not clear was how they sensed something to which to adhere. It turned out to be shear, according to UT findings.
The bacteria are generally harder to kill when attached and may evolve a resistance to the agent used to kill them. Non-sticky surfaces also have not worked as a countermeasure because the bacteria are persistent and have many ways to attach.
Lead researcher Vernita Gordon concluded that a third way to prevent the gunky buildup is to engineer a surface with some property that fools the bacteria into thinking there is nothing to adhere to.
“It’s important to prevent biofilms before they start,” Gordon said. “It’s much easier to wipe out free-floating bacteria than a biofilm.”
The fix is not immediately clear. Gordon and her colleagues — UT researchers Christopher Rodesney, Brian Roman and Numa Dhamani, among others — will be investigating materials that could fool the bacteria or otherwise prevent them from detecting shear, according to a university statement.