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London – British researchers have discovered a new strain of Streptococcus pyogenes that produces significantly more exotoxin A and is believed to be responsible for the rise in invasive scarring disease that has emerged in England and Wales since 2016. Outside the country, according to the report, M1UK is the name of a new tribe Lancet Infectious Diseases (2019; doi: 10.1016 / S1473-3099 (19) 30446-3) has almost never happened so far. Streptococci continue to respond well to antibiotics.
Scarlet fever, which killed many children in western countries by the early 20th century, has become much rarer even before the discovery of antibiotics (except in poorer countries, with an estimated half a million children annually). The reasons for the decline in higher income countries are unknown. However, the researchers suggested that the less pathogenic Group A beta-hemolytic streptococci displaced earlier strains.
Currently, the diseases are relatively mild. Mostly, only pharyngitis occurs, which is quickly treated with antibiotic treatment. Increases in scarlet fever have been reported in England and Wales since 2014, which was usually mild in the first few years. Since 2016, invasive diseases have been on the rise. This led the team led by Shiranee Sriskandan from Imperial College London to genetically study the pathogens.
First, it was observed that the proportion of emm1 strains of S. pyogenes found in throat swabs increased from 5% in 2014 to 33% in 2016. The share of invasive diseases increased from 31% in 2015 to 42% in 2016. Previously, most infections were triggered by the strains emm3 and emm4. The classification of bacteria is based on the emm gene, which contains a blueprint for the M protein on the cell wall of A streptococci.
Accurate genome analysis revealed that the em1 strain had changed genetically. Exact mutations (single nucleotide polymorphisms, SNPs) occurred at 27 sites in the genome. According to Sriskandan, they are found in regulatory and metabolic genes. 3 SNPs have been detected in the rofA gene, which normally slows down the production of SpeA (streptococcal pyrogenic exotoxin A).
SpeA is the toxin responsible for the rash. According to Sriskandan, mutations in rofA are likely responsible for increasing SpeA production. The new strain, which the researchers refer to as M1UK, produces 9 times more SpeA than other emm1 strains (190 ng / ml vs. 21 ng / ml).
In England and Wales, M1UK could be responsible for the rise of scarlet fever (with rash) and the rise of invasive diseases (such as sepsis). The proportion of M1UK in all emm1 isolates was 84% posterior. Outside the island, M1UK seems to be rare. Analysis of 2800 genome isolated cases were reported in the US and Denmark alone.
Sriskandan points out that the M1UK strain, like other S. pyogenes strains, still responds well to antibiotics. Even with invasive diseases, the chances of recovery are good. Resistance would be hard to see so far. © Heat / equilibreplus.com