During their hospital stay, seven percent of all patients in industrialized countries develop diseases that they did not have prior to hospitalization. These hospital infections are referred to as nosocomial infections. As a team of researchers from the Swiss Federal Laboratories for Materials Science and Technology (Empa) and physicians from the Cantonal Hospital of St. Gallen in Switzerland report, such infections can lead to serious illnesses and even to potentially fatal blood poisoning.

Such diseases can develop with particular ease whenever tubes are involved, for example for respiration or hydration. The reason for this are biofilms, accumulations of germs on surfaces, which spread, for example, in urinary catheters. “If you want to design materials that prevent the formation of biofilms, you first have to clarify how this hazardous growth of germs occurs in the first place,” Dr. Qun Ren and her team of researchers write. Until now, this has remained largely unexplained.

“The most successful flat-sharing community in the world”

Because a biofilm is no ordinary contamination, which can be destroyed using antiseptics or antibiotics, but rather “the world’s most successful flat-sharing community”, as the researchers call it. They are “accumulations of bacteria embedded in a matrix of self-produced mucous, which behave like a single large organism”. Biofilms are a real “success model”; they have been found in the oldest known fossils in our geologic history.

Thanks to a gel-like layer of biopolymers, the bacteria living in these “communities” are protected, mobile, and interconnected. “There is a lively exchange of useful genetic material, communication via chemical signals, and reporting to the surface when the deeper layers of the “shared household” are hungry.” When necessary, they send a troop of trailblazers to a new location and establish new colonies, just like a metastatic tumor.

Like a gecko on a window

“A crucial event in the formation of a biofilm is the moment when freely moving bacteria attach themselves to a surface,” Dr. Ren explains. The bacteria use the same forces as geckos when they scramble around on windows. In order to create new materials that prevent this adhesion, the researchers simulate real-life conditions in the laboratory, for example those found inside a catheter.

Their samples originate from patients at the Cantonal Hospital of St. Gallen who within three weeks of having received a stent or catheter, developed a mild infection. In spite of the moderate severity of the biofilms, the researchers found that certain types of germs often occur together in a specific group.

The next step will be to clarify the relationship between such groups and the risk of hospital infections. In addition, the special design of surfaces for specific germ carriers is currently being discussed.