New form of invasive flesh-eating bacteria strain found
This illustration depicts a three-dimensional computer-generated image of a group of erythromycin-resistant Group-A Streptococcus (GAS), also known as S. pyogenes, bacteria. (CDC/ James Archer)
Published Sunday, July 19, 2015 9:05AM EDT
Researchers in Britain have stumbled upon a new variant of a strain of strep bacteria that is already contributing to a rise in dangerous illnesses in both Canada and elsewhere.
They say this new form of a strain of Group A Streptococcus (GAS), called emm89, is the likely reason why severe forms of one strain of the bacteria are on the rise.
Group A Strep is a family of bacteria that often lives in the throat and on the skin without causing any illness at all. The bacteria can cause mild infections, including scarlet fever or strep throat, or in rare cases, more severe, invasive infections, such as sepsis and necrotizing fasciitis, also known as flesh-eating disease.
These infections, which have been on the rise since the 1980s, can be highly dangerous, with a fatality rate of about 20 per cent. A girl in New Brunswick recently made headlines when what appeared to be strep throat suddenly developed into a full body infection that caused her to lose parts of all four limbs.
Most severe strep infection in Canada is caused by a strain called emm1, but researchers in Canada and elsewhere have noticed a sharp rise of severe infections caused by emm89 in the last 20 years.
To figure out why this strain was on the rise, researchers at Imperial College London sequenced the genes of several emm89 samples taken from patients recently infected with invasive strep.
They found a new subtype of emm89 that has two distinguishing features: it produces more toxin, and it has lost its outer capsule, which may make it better able to stick to surfaces and perhaps be more transmissable. Their findings appear in the journal mBio.
Dr. Liane Macdonald, a physician in communicable disease prevention with Public Health Ontario, says the discovery of this new variant of emm89 is interesting, but not necessarily a cause for concern yet.
"Certainly, it's of interest," she told CTVNews.ca, noting that even among rare serious GAS infections, emm89 makes up only about 10 to 20 per cent of cases.
Macdonald says emm89 has not been as well-studied as many researchers would like. "So this study helps us to better understand how the disease is evolving," she said.
The vast majority of strep infections are still mild. Macdonald says, and there is no evidence that this new subtype will cause more invasive illnesses. Still, the development merits vigilance.
"It's new information to monitor," she said.
Canadians can still protect themselves from strep and other bacterial infections by remembering to practice good personal hygiene, washing hands, covering up sores where bacteria can enter and not sharing drinks and toothbrushes.
She also advises that those with mild illness who suddenly develop fever, severe pain, or trouble moving their neck could be at risk of developing one of the more severe forms of Group A Strep and should see a health care provider quickly.