Scarlet fever epidemics were deadly to children across the globe in the 1800s, but in recent decades concerns about the disease have largely faded from the minds of medical experts, in part due to the power of antibiotics.
Key points:
- The bacteria causing scarlet fever has acquired toxins called superantigens
- It is believed to have played a role in recent scarlet fever outbreaks in Asia and the UK
- The superantigens have increased the virulence of the disease, researchers say
Recently though, the bacteria responsible for scarlet fever has been mutating and making a resurgence.
New research by scientists at the University of Queensland (UQ), in collaboration with scientists around the world, has suggested the Streptococcus pyogenes bacteria is growing stronger after being infected by viruses.
UQ Australian Infectious Diseases Research Centre director Mark Walker co-authored a paper on the topic that was recently published in the journal, Nature Communications.
Professor Walker said they started looking into Streptococcus pyogenes after an outbreak in Asia in 2011 and then in the UK in 2014.
Between 2014 and 2018, the UK National Health Service reported a 68 per cent increase in the number of lab reports of pyogenic streptococci.
Scarlet fever was once widely feared by parents because of its harsh effects on children.
Historically, septic complications such as brain abscess, meningitis, lung abscess, pneumonia, osteomyelitis (bone infection), middle ear and soft tissue infections could follow scarlet fever and cause early death.
According to ABC Health and Wellbeing, typical scarlet fever symptoms are a sore throat, sudden high fever, enlarged lymph nodes in the neck, and a rough, bright red rash on stomach and limbs.
'Three new genes'
Professor Walker said while one might expect that a virus infecting a bacteria was bad for the bacteria, this is not always the case.
"One of the big stand-outs for us was the presence of these three new genes," he said.
Professor Walker said the genes turned out to be from three viruses which had been "floating around" for a while but only recently have all come together.
"It was quite a surprise," he said.
"They (the bacteria) seem to have acquired a number of toxins that are called superantigens," Professor Walker said.
"These things are able to trigger the body's own immunity and that then results in a fever and a rash.
"We've been able to show that together, these three toxins have increased the virulence of Streptococcus pyogenes and also made it better able to colonise in an animal model."
'Better able to colonise the host'
Professor Walker said normal scientific thinking had been that a virus infecting a bacteria was bad for the bacteria.
"But in this case, the bacterial virus is carrying three new toxins and because it's carrying those toxins when it infects the bacteria, it gives the bacteria this extra virulence potential.
"We hypothesise that this allows the bacteria to better able to colonise the host.
"Because the bacteria is then able to last longer inside a child … this new combination of toxins has time to act and then that, we think, is the trigger for this resurgence."
Professor Walker said the toxins were particularly invasive as several targeted white blood cells — usually a key defence against foreign bacteria.
"Those toxins allow the bacteria to escape the white blood cells that are coming to the site of infection," he said.
Professor Walker said while scarlet fever was not causing lethal infections as it used to it was important to continue to highlight infection and vaccine research as outbreaks continued.
"There is no vaccine and what we've relied on previously is antibiotics to help treat infection when it occurs," he said.
"Streptococcus pyogenes is still susceptible to many antibiotics, but it's also gaining resistance.
"Developing vaccines to keep infection under control is a really important concept and goal."
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2020-10-07 19:53:00Z
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