Study unmasks bacterial motion

A group of Yale researchers may be on the way to saving millions of dollars currently spent to treat infections arising from catheter use.

In a study published in Physics Review Letters on Feb. 6, Yale researchers Hur Koser, Jane Hill and Jonathan McMurry — all from different departments — found that flagellated bacteria tend to move to the left when flowing downstream, eventually reversing course and swimming upstream. This allows them to adhere to crevices on the left wall, promoting infection, which may help explain why urinary tract infections often occur in patients using catheters, electrical engineering professor Koser said.

Koser said the team began by observing how bacteria, especially motile bacteria such as E. coli, respond to different concentration gradients, including chemical concentration gradients. The research found that bacteria move to the “left” of the surface regardless of the chemical concentration gradient, he said. Bacteria may become trapped in crevices or imperfections on the left wall and possibly cause further infection, he said.

Koser said he was interested in studying bacterial hydrodynamics because understanding bacterial behavior is often key in understanding the behavior of larger cells.

“Bacteria being simple cells, it’s critical to understand them,” he said.

For this experiment, Koser’s team set up a simple system with walls and a flow to observe bacterial hydrodynamic behavior.

Hill, a postdoctoral associate in chemical engineering, said this phenomenon occurs in any kind of plumbing, from catheters to garden hoses. Because bacteria can swim upstream to the left, they may show up in unusual locations, Hill said.

“Basically any system [where] we have a flow and wall, we have bacteria that can orient themselves,” she said. “You’re likely to find bacteria where we normally wouldn’t expect them to be.”

This phenomenon may explain plumbing problems caused by bacterial growth in pipes, Koser said. The bacteria can create serious health problems by contaminating drinking water, he said, but this research may make it possible for bacterial movement upstream to be slowed down or even stopped.

A more immediate benefit of the research may be preventing urinary tract infection in patients using catheters. According to Kelly Karns ’07, an undergraduate student in Koser’s lab, up to three out of every four patients with catheters suffer from this problem.

“The possibility of decreasing that risk would be a huge impact on the history of medicine,” she said. “[It would save] the doctor’s money and the patient’s money as well.”

Hill said the next step is to investigate whether this phenomenon is in fact relevant to urinary tract infection and why it occurs so often. The team also plans to investigate the application of its study in solving problems like E. coli outbreaks, she said.

“I really hope that more people join in on the research and take it to different places,” Hill said.

At the time the research was completed, McMurry was a member of Yale’s Molecular Biophysics and Biochemistry Department, but he is no longer part of the Yale faculty. The work was conducted and published in collaboration with Ozge Kalkanci at Bogazici University in Istanbul, Turkey.

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