Scientists figure out how flesh-eating disease works

HELENA – Scientists at Rocky Mountain Laboratories in Hamilton say they have figured out how the bug behind flesh-eating syndrome overcomes the body’s immune system.

In a paper published last week in the online version of the Journal of Immunology, Frank De Leo and his team of scientists show that group A Streptococcus bacteria senses the body’s impending immune attack and can survive even the most intense onslaught of the body’s innate defenses.

Group A Strep causes strep throat, rheumatic fever and the potentially deadly, deep infections known as flesh-eating syndrome.

The paper comes less than a year after De Leo and his team showed that strep can defeat the body’s front-line immune cells – the neutrophils – by commanding them to kill themselves.

“For anything to cause infection, it has to evade the neutrophil,” De Leo said.

Neutrophils typically wipe out unwelcome pathogens quite efficiently. Neutrophils kill by “swallowing” an individual pathogen and sequestering it in a sack, De Leo said. It then pumps microbe-killing agents into the sack. Afterward, the neutrophil kills itself.

But strep senses the immune system coming.

If they can initially sense the first few (immune system) cells that come in, then the subsequent bacteria that are growing and dividing are ready.” Neutrophils swallow the strep, he said. They put the bug in its special sack and let loose with their arsenal. But even as the neutrophil immune system attacks the bug’s cell wall, strep is building it back up again. All the while, the bug is somehow telling the neutrophil to kill itself. The strep then escapes and proliferates, he said.

De Leo is not a drug researcher, but his work sheds new light on how strep infections happen and how they might be stopped.