New Strain of Group A Strep Bacteria Discovered by UK Investigators

Investigators in the United Kingdom have announced their discovery of a new strain of Group A Streptococcus bacteria. According to the investigators the new strain, M1UK, appears to have emerged in England and Wales around 2010 and has become a dominant cause of Strep A infections.

The research, led by investigators from the Imperial College of London, was published in The Lancet Infectious Diseases.

During the spring of 2016, the investigators noticed a 1.5x increase in the number of laboratory-confirmed invasive Group A strep infections recorded in comparison with the previous 5 years. A surge in cases of scarlet fever, which is caused by Group A Strep, was also observed during this time.

Based on these observations, the team set out to determine if the bacteria causing Strep A infections were changing in any way. To do so, the investigators accessed data from a biobank that collects bacterial strains from across North West London.

For this part of the research, the team analyzed infections that occurred between spring 2014-2016 to identify the main genetic subgroups causing scarlet fever or common throat infections. Based on the data, the team concluded that although most cases in 2014 were caused by strains emm3 and emm4, infections of emm1 strain increased year-over-year and were responsible for 5% of cases in 2014, 19% in 2015, and 33% in 2016.

This finding led the research team to hypothesize that the emm1 strain may have changed in some way. To determine the validity of this hypothesis, they evaluated the genomes of all emm1 strains in North West London between 2009 and 2016.

During this stage, the team identified the new strain type within the emm1 group, which differed from the other emm1 strains by 27 genetic mutations. They also determined that the new strain produced 9 times the amount of streptococcal pyrogenic exotoxin A than other emm1 strains, which could explain the rise in Strep A cases.

To gain insight on how often the new strain was occurring, the investigators looked at 552 samples of emm1 invasive Strep A collected from Wales and England between 2013 and 2016. The team found that 77% of cases were caused by the newly identified M1UK strain.

After looking at 2800 genome sequences from across the world, 1 case of M1UK was detected in Demark and the United States, respectively.

Based on these findings, the team is now calling for global vigilance to identify cases of the new strain across the world and highlight the importance of developing a vaccine against strep A.

"The emergence of this new strain suggests we may need increased surveillance of the type of strains causing scarlet fever, throat infections and sepsis—both at a UK and global level,” Dr. Nicola Lynskey, a co-author of The Lancet report said in a press release.