Bacterial biofilms—dense colonies of bacteria that form virtually impenetrable structures on hard surfaces—are increasingly dangerous. They are thought to cause millions of infections each year, leading to death, illness and increased health care costs, including for people with implanted medical devices.
Biofilms are especially common in medical devices inside the human body, such as knee replacements, pacemakers, and catheters. Once biofilm forms, it is almost impossible to get rid of. Antibiotics have no effect. Immune cells cannot fight this.
A team of researchers from the University of Texas at Austin and other institutions has found clues to how bacteria form biofilms. This discovery could eventually lead to new coatings on medical devices that could help stop the formation of biofilms.
In a recent paper in the journal npj Biofilms and Microbiomes, the team found that bacteria landing on thicker, softer gel coatings were less likely to receive a signal to begin biofilm formation compared to bacteria on thinner, stiffer coatings.
“When bacteria encounter a hard surface, they receive signals and their gene expression changes so that they begin to form biofilms,” said Vernita Gordon, an assistant professor of physics at the University of California, Austin, and an author of the paper. “We wanted to find out what it is on the surface that is sending this signal.”
Researchers have found that bacteria undergo mechanical changes when they come into contact with certain hard surfaces. Think of bacteria as tiny bean bags tossed onto a soft cushion or cloth-covered table. Both land on the cloth and each bean bag ends up squishing, but the bag that lands on the table squishes more. The more the bacteria squish, the stronger the signal that the bacteria has landed on a hard surface. It is this signal that prompts the bacteria to begin turning into biofilm.
The team experimented with different gel coatings on rigid materials. The gels were identical in surface but had different thicknesses. The researchers found that the thicker the gel, the less the bacteria were subject to mechanical changes and the less likely they were to form biofilms. Thinner films were more likely to cause bacteria to shrink and form biofilms.
“Medical devices are typically made from materials that are stiffer than the living tissue that surrounds them,” Gordon said. “There has been a lot of discussion about coatings on devices that prevent biofilm formation, such as antibiotics or antimicrobials. However, over time, bacteria develop resistance to them. But what if we could stop bacteria from finding a hard surface?”
That’s why Gordon and his team focused on the physical properties of materials and how bacteria interact with them. If physical properties could be combined with antibiotics or chemical repellents, coatings on medical devices could protect against biofilms at multiple angles, reducing the likelihood of bacteria adapting and evading preventive measures.
“We’re working to make sure this research has real benefits,” Gordon said. “The next step is to collaborate with materials scientists and engineers to experiment with coatings on devices, and we plan to do this with catheters.”
Liyun Wang, Yu-Chen Wong, Joshua M. Correira, Megan Vancura, Catherine A. Brown, Berkin Dortdivanlioglu, Lauren Webb and Elizabeth Cosgriff-Hernandez of UT Austin, Chris J. Geiger, Shanice S. Webster and George A. O’ Toole of Dartmouth College, Ahmed Touhami of the University of Texas Rio Grande Valley, and Benjamin J. Butler and Richard M. Langford of the University of Cambridge also contributed to the study. The research was funded by the Cystic Fibrosis Foundation, the National Science Foundation, the National Institutes of Health, the University of Texas Planet Texas 2050 Breaking Barriers Initiative, and a grant from the UT College of Natural Sciences.