Streptococcus pyogenes bacteria on a blood agar plate

A type of flesh-eating bacteria called Streptococcus pyogenes dots a lab dish. Credit: Rodolfo Parulan Jr/Getty

Microbiology

Flesh-eating bacteria thrive on pain

Microbes weaken host’s immune response by triggering pain neurons.

Flesh-eating bacteria flourish by hijacking pain neurons and turning them against the body’s immune system.

The bacterium Streptococcus pyogenes is known for destroying skin and soft tissue, and causing excruciating pain during the early stage of infection. To work out whether this pain is related to the microbe’s survival strategy, Isaac Chiu at Harvard Medical School in Boston, Massachusetts, and his colleagues injected the paws of mice with various strains of S. pyogenes. They found that a toxin it produces, called streptolysin S, is crucial for stimulating pain-sensing neurons to fire, which in turn sends signals to immune cells in the infected tissue.

The researchers found that these neuronal signals curtail the body’s immune response, thus allowing the bacteria to thrive. When the team blocked the neurons’ signals, the immune system was able to fight off the bacteria — a finding that the authors say could lead to a treatment for S. pyogenes infections.