A new study by researchers at Princeton University, Princeton, NJ, examined how bacteria clogs medical devices, and found that the microbes join to create slimy ribbons that form tangles, trapping other bacteria, and creating a full blockage in a very short period of time. Their findings, they say, could help shape strategies to prevent clogging of devices such as stents.
Using time-lapse imaging, they monitored fluid flow in a narrow tube similar to those used in medical stents with rough rather than smooth surfaces and pressure-driven fluid instead of non-moving fluid. The team of biologists and engineers placed a small number of bacteria that are common contaminants of medical devices into the tube and waited.
Within about 40 hours, they observed that some of the microbes, which had been dyed green for better visibility, had attached to the inner wall of the tube and began to multiply, eventually forming a slimy coating of biofilm, which consists of thousands of individual cells held together.
For several hours, the researchers sent additional red-dyed microbes into the tube. These red cells became stuck to the biofilm-coated walls, where the force of the flowing liquid shaped the trapped cells into streamers. During this time, the fluid flow slowed only slightly.
At about 55 hours into the experiment, the biofilm streamers tangled with each other, forming a net-like barrier that trapped additional bacterial cells, creating a larger barrier which, in turn, ensnared more cells. Within an hour, the entire tube became blocked and the fluid flow stopped.
"For me, the surprise was how quickly the biofilm streamers caused complete clogging," said Howard Stone, a professor of mechanical and aerospace engineering. "There was no warning that something bad was about to happen."
The research was published in the Proceedings of the National Academy of Sciences.
