It is imperative to look into the connection between circulating S. pyogenes and cases of invasive illness in light of the rise in group A Streptococcus (GAS) infections in England.
Scarlet fever and pharyngitis are caused by S. pyogenes. An increase in pharyngitis or scarlet fever infections is a public health concern since emm1 S. pyogenes strains are disproportionately connected to invasive infections and have a high level of virulence.
In the past eight years, invasive S. pyogenes infections and scarlet fever have increased in England. Nevertheless, during the coronavirus disease 2019 (COVID-19) pandemic, this increase decreased. Notably, invasive infections significantly increased between 2015 and 2016, which had never happened before.
Numerous factors, including strain-specific virulence, underlying illnesses, genetic susceptibility, exposure history, and viral co-infection, have been found to increase susceptibility to S. pyogenes infection.
Scarlet fever and invasive infections were brought on by the introduction of M1UK, a fresh sublineage of emm1 S. pyogenes, in England.
It goes without saying that this new strain outperformed the earlier emm1 M1global strain, which appeared and spread around the world in the 1980s.
Superantigenic scarlet fever toxin SpeA production by M1UK strains is one of the factors contributing to this out-competition (streptococcal pyrogenic exotoxin A).
Ssa and spec, two more phages expressing superantigen genes, and a single-nucleotide polymorphism were discovered. (SNP). The upregulation of SpeA in the M1UK lineage is brought on by several causes.
In the UK and many other European nations, including Denmark and the Netherlands, M1UK has been discovered. Additionally, the lineage has been found in Australia, Canada, and North America.
According to the Active Bacterial Core surveillance system, emm1 isolate infections are uncommonly severe in the US. After the COVID-19 limits were lifted, an increase in GAS infections was seen all across the world. This underscores the significance of expanding global surveillance for lineages like M1UK.
Concerning the study
Although whole-genome sequencing methods have been used to identify genetic differences between the M1UK and M1global strains, most nations lack the necessary capability.
The rofA, gldA, and pstB genes were used in the current work to develop an allele-specific PCR (AS-PCR) approach to find M1UK-specific SNPs.
In order to distinguish the M1UK and M1global strains from other, less frequent intermediate sublineages, amplification targets were chosen. Based on the DNA from the control strains of each lineage, the PCR conditions were adjusted for the amplicons.
At Imperial College, samples were taken from the infectious bioresource. To test whether the rofA and pstB primers could distinguish lineages of 27 recently genome-sequenced noninvasive emm1 S. pyogenes strains obtained between 2017 and 2018, allele-specific PCR was conducted.
To ensure the existence of sufficient numbers of each lineage, the isolates for M1global strains were artificially enriched; hence, out of the 27 isolates, eight were M1global and 19 were M1UK.
Sixteen strains from the M1global, M113snps, M123snps, and M1UK lineages, as well as intermediate sublineages, were collected between 2013 and 2016 to determine whether AS-PCR could identify emm1 isolates from these sublineages.
All research isolates had accurate SNP detection in the rofA gene, which is significant. SNPs were only found in the gldA genes of the M123snps and M1UK isolates, but not the M1global or M113snps isolates.
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SNPs in pstB were only found in isolates from M1UK. These results demonstrated that AS-PCR was capable of reliably determining SNP profiles.
In 2020, there was a decline in common respiratory diseases in England, including emm1 S. pyogenes infection. It’s possible that the statewide limits put in place to stop the COVID-19 pandemic are to blame for the decline in infection rates.
AS-PCR was used to analyze 305 invasive emm1 S. pyogenes isolates from 2020. RofA, gldA, and pstB M1UK-specific SNPs were found in 91% of the isolates.
The remaining isolates were classified to M1global since no SNPs were discovered in them. It’s interesting that AS-PCR failed to detect any emm1 strains of the intermediate lineage.
The results of the AS-PCR method showed that invasive S. pyogenes would continue to spread the M1UK lineage in England between 2016 and the end of 2020.
The M1UK sublineages have been successfully identified using the AS-PCR screening approach. This assay needs to be verified in lab settings in the future.
Long-COVID prevalence among English schoolchildren: Research indicates extensive effects on health and wellbeing
More than 50% of children infected with invasive infections in England during the 2022–2023 season had emm1 S. pyogenes. This data suggests that the M1UK lineage has persisted as the dominant one in England, necessitating ongoing monitoring.