Researchers at the University of Queensland in Australia studied the scarlet fever pathogen Streptococcus pyrogenes from recent outbreaks of the disease. The researchers found that the bacterium had inherited genes from certain viruses, making the pathogen more toxic, infectious and resistant to some common antibiotics. The team recently presented its study results in the renowned scientific journal “Nature Communications”.
Antibiotics and penicillin have almost eradicated the infectious disease scarlet fever. In recent years, however, the number of cases worldwide has increased more than fivefold. A research team has now found the reason for the comeback of the childhood disease and discovered that the bacterial pathogen is more aggressive than ever before.
Scarlet fever is once again on the rise worldwide, after the infectious disease was almost eradicated in the 1940s. An international team of researchers showed that a strain of the bacterium Streptococcus pyogenes has acquired so-called prophages. This is viral DNA that has been incorporated into the genetic material of bacteria. This new strain is responsible for the resurgence of the disease.
Health authorities around the world were surprised when some Asian countries reported increased scarlet fever cases again in 2011. “The disease had largely disappeared by the 1940s,” reports research director Dr. Stephan Brouwer. In 2014, a major outbreak followed in Great Britain. For some time now, the pathogens have also been discovered in Australia.
Scarlet bacteria with virus genes
“This worldwide recurrence of scarlet fever has led to a more than five-fold increase in the incidence of the disease and to more than 600,000 cases worldwide,” Brouwer emphasized. The researchers have now been able to find the cause for the resurgence of the centuries-old childhood disease.
As the research team explains, a population of scarlet fever bacteria was infected by viruses carrying toxin genes. As a result, parts of the viral DNA incorporated into the genome of Streptococcus pyogenes and formed a new strain of the pathogen called North-East Asian serotype M12 (emm12) Streptococcus pyogenes. These offshoots contain so-called “superantigen toxins”, which make the pathogen more dangerous.
“We have shown that these acquired toxins allow Streptococcus pyogenes to better colonize its host,” explains study co-author Professor Mark Walker. The results from animal models also pointed to this. The researchers removed the toxin genes from the pathogen, whereupon the pathogen was no longer able to multiply as effectively in experimental animals.
Scarlet fever is back: The comeback of the childhood disease
In the course of the health-political measures for the control of COVID-19 also a strong decrease of the scarlet fever cases is to be expected. “This year, the social distancing due to COVID-19 has kept the scarlet fever outbreaks in check for the time being”, adds Professor Walker. When the measures against COVID-19 are completed, however, a renewed increase in scarlet fever cases is likely. “We need to continue this research to improve diagnosis and better manage these epidemics,” concludes Walker. (vb)
“Just like the coronavirus SARS-CoV-2, which causes COVID-19, Streptococcus pyogenes bacteria are usually spread by coughing or sneezing, with symptoms such as sore throat, fever, headache, swollen lymph nodes and a characteristic scarlet skin rash,” explains study leader Brouwer. Scarlet fever affects mainly children aged between two and ten years.
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