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Scientists decipher the mechanism behind the progression of meningitis

Julien Husson, from l’X’s Hydrodynamics Laboratory, and Raphaël Voituriez, CNRS researcher at Sorbonne University and lecturer at l’X, are two members of a research consortium that discovered that the bacteria that are responsible for meningitis “flow” in blood vessels. This key stage of the infection is described in the May 17, 2018 issue of Cell.

Meningitis infections in humans is characterized by an accumulation of bacteria, the meningococci, which multiply and can invade blood vessels. A research team led by Guillaume Duménil at Institut Pasteur, in collaboration with several teams of physicists, discovered that these bacteria behave like a viscous fluid with original properties that had never been described. They published their results in the prestigious scientific journal Cell on May 17, 2018.

To study these bacteria, the researchers used micropipettes, which are the specialty of Julien Husson, now research scientist at l’X’s Hydrodynamics Laboratory. By aspirating aggregates of bacteria in these micropipettes, the researchers found that meningococci flowed like honey, with the unexpected properties of a viscous fluid. Grouped together in this way, the bacteria adapt to the shape of blood vessels and grow like a jelly to colonize their host entirely, to the point of causing fatal hemorrhages.

When examined on a smaller scale, the “pili” of these bacteria become visible. These extremely fine hairs (50nm), which grow and retract continuously, enable the bacteria to communicate with each other, exchange genetic material, and move closer together and farther apart in seconds. This process of interaction gives the meningococcal aggregates a greater diffusion capacity than that of an isolated bacteria, thereby revealing a new type of active matter, based on the attractive force of the pili.

The research consortium combined an experimental approach with a theoretical model developed by Raphaël Voituriez, CNRS researcher at Sorbonne University and lecturer at École Polytechnique, in collaboration with Hugues Chaté (CEA, CNRS, Paris-Saclay University), to reproduce the behavior of these bacteria by numerical simulations.

The interdisciplinary study was made possible thanks to a close collaboration between a laboratory specialized in meningococcal infections (G. Duménil, Institut Pasteur and Inserm) and physicists from the teams of Nelly Henry (CNRS, Sorbonne University), Raphael Voituriez, and Hugues Chaté. This cooperation allowed the researchers to couple a quantitative experimental approach with active matter physics modeling to gain a better understanding of this very particular mode of infection.