Urinary tract infections affect nearly 150 million people per year, representing the second most frequent bacterial infection after respiratory infections. Their recurrence rate is high, and they can become chronic in some people. In a study published on May 26 in the journal Science Immunology, researchers from the Mucosal Inflammation and Immunity Unit at the Institut Pasteur and Institut Cochin looked at the immune responses of the host to bladder infections.

"We found that certain white blood cells, called memory T cells, appear during a first infection. These cells are called 'resident', because they develop in the bladder during the infection and then stay there to fight subsequent infections," explains Matthieu Rousseau, researcher in the unit and first author of the study. These lymphocytes have been transformed by the host immune system to specifically recognize the bacteria causing these infections and eliminate them quickly and efficiently.

These highly effective defense cells, however, suffer from our treatment options. "We have observed that antibiotics, depending on when they are used, can interfere with the development of these memory T cells. In the long term, bacteria can even become resistant to these antibiotics," says Molly Ingersoll, director of the unit and the study's last author. A double punishment for this line of defense, which reminds us of the consequences that certain consumption patterns can have on our health.