Recently, the scientists who were studying scarlet fever have identified a new bacterial strain in England and Wales. This strain has led to an increase in more serious strep A infections.
The scientists have found these results from the cases in London, Wales, and England during 2014 – 2016. And “The Lancet Infectious Diseases” journal presented these results.
Capability to produce scarlet fever toxins
In 2014, there was a sharp increase in the UK’s cases of scarlet fever since the 1960s. The number of cases was 15,000 in 2014. That increased to 17,000 in 2015, and more than 19,000 by 2016. The symptoms in children include a high temperature, pink-red rash, and sore throat.
Strep A bacteria was the cause of scarlet fever. While the disease was easily treatable with antibiotics. Moreover, the cases of invasive infections caused by these bacteria have also enhanced in 2016, in contrast to the previous five years.
In this study, the team has found a new bacterial strain with an increased ability to produce toxins of scarlet fever. Also, this new bacterial strain can cause all types of strep A infections. So, it has become vital to globally monitor these bacteria.
Later, the research team has tried to identify this new bacterial strain based on the type of emm gene present. The team found that the strep A strain types emm3 and emm4 led to the initial upsurge in the cases of scarlet fever in 2014. But, in the spring of 2015 and 2016, the emm1 strain was more dominant in causing throat infections.
In spring 2014, emm1 strains accounted for only 5% of bacterium isolates collected in Northwest London. But this percentage increased to 19% by 2015. And in 2016, it became 33%, making emm1 the single most frequent strain.
Further study showed that emm1 strains were also increasingly dominant in causing severe invasive infections in the UK and Wales. In Spring 2015, 31% of the invasive strains collected were of emm1 isolates. But by spring 2016, emm1 strains increased and accounted for 42% of the invasive strains.
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Represents 84% of all Strep A genomes analyzed in England and Wales
For further research on emm1 isolates, the team sequenced the genomes of 135 non-invasive emm1 isolates, collected in northwest London during 2009 – 2016. And 552 invasive emm1 isolates from UK and Wales, collected during seasonal spikes of disease between 2013 and 2016.
Later, the team compared the sequence of both isolates with one another. And also analyzed the level of toxins produced by different emm1 strains. The study results found that the majority of emm1 strains from 2015 – 2016 were breakaway emm1 clone, referred to as M1UK.
This clone had 27 mutations and was related to increased production of toxin SpeA. The SpeA toxin can trigger scarlet fever and lead to some invasive infections and Strep A pharyngitis. Also, M1UK produces nine-folds more toxin than any other emm1 strain.
In 2016, M1UK accounted for 84% of all emm1 genomes assessed in the UK and Wales. And became the dominant cause of serious emm1 Strep A infections. An increase in the activity of Strep A, along with the upsurge of scarlet fever may have provided conditions needed for M1UK to adapt genetically and spread in England.
Up till now, M1UK appeared to be limited to the UK. But two examples of its identification in a different place have suggested that M1UK has the potential to spread in other countries. While further research on this strain can provide more insights.