Group A Streptococcus (GAS) is a bacterium that infects 600 million people a year. The bug is a relative of the version that most commonly causes strep throat, but it is not limited to this area of the body. Most GAS cases are mild and involve symptoms like minor throat or skin infections, but the microbe can cause severe, life-threatening problems such as necrotizing fasciitis (where the bacteria destroys the skin), pneumonia and blood poisoning.
Worringly, a new virulent version of A Streptococcus has been on the rise in recent years. Called emm89, it now causes as many as 1,800 serious infections per year in the United Kingdom and Ireland, and has also turned up in Japan, Sweden and Canada. One-fifth of those with serious emm89 infections die, according to a study published in the microbiology research journal mBio. This strain appears to be more likely than other GAS varieties to cause life-threatening problems like blood infections and pneumonia.
Researchers from the Imperial College London noted that the number of infections caused by this strain have risen sharply in recent years. In the United Kingdom, infections increased by 80 percent between 2005 and 2007 alone. emm89 now causes one-fifth of serious strep infections in Britain.
Researchers also noted with some astonishment that, unlike other bacteria in the group, this strain has evolved to lack a “capsule,” or membrane-like covering, making it more virulent.
“The fact that it had lost its capsule was a complete surprise, because it was believed that the capsule was essential for group A streptococcus to cause invasive disease,” said Claire Turner, a scientist at Imperial College London who led the study, in a statement. “We know that without a capsule, they stick better to surfaces, so that may help them to transmit more easily. Another possibility is that they can more easily get inside human cells, which makes them harder to treat.”
Shiranee Sriskandan, the senior author of the research said, “We know very little about how group A streptococcus is transmitted from person to person. We need to look into this more deeply and think about better ways to prevent transmission.”
Currently, the strain remains quite easy to treat with antibiotics, but hopefully it will not develop resistance to antibiotic treatment.