Group A streptococcal (GAS) infections amongst children in Europe: Taming the rising tide

editorial

. 2022 Dec 15;51:101071. doi: 10.1016/j.nmni.2022.101071

What is the M1_UK strain?
GAS strains are classified based on the emm type that is determined based on the amino acid sequence of a protein found on the bacterial cell wall (M protein). There are currently >220 known strains based on emm classification. In developed countries, the most common emm types include emm1, emm3, emm12, and emm28. These are also the types mostly isolated from asymptomatic carriers. Based on disease severity, emm1, emm3, and emm49 are associated with invasive disease whilst emm2, emm4, emm6, emm12, and emm44/61 are associated with superficial disease. M1_UK (M1T1 S. pyogenes) is a mutant strain of GAS within the emm1 family that was discovered in 2019 but has been in circulation since 2010. The strain differs by just 27 mutations when compared with other emm1 family strains which allows it to increase the production of streptococcal pyrogenic exotoxin A (SpeA) by more than nine-times. This makes the strain fitter and more dominant in the society. It was designated as the largest single contributor to both non-invasive and invasive infections in 2016.

What is the M1_UK strain?

GAS strains are classified based on the emm type that is determined based on the amino acid sequence of a protein found on the bacterial cell wall (M protein). There are currently >220 known strains based on emm classification. In developed countries, the most common emm types include emm1, emm3, emm12, and emm28. These are also the types mostly isolated from asymptomatic carriers. Based on disease severity, emm1, emm3, and emm49 are associated with invasive disease whilst emm2, emm4, emm6, emm12, and emm44/61 are associated with superficial disease.
M1_UK (M1T1 S. pyogenes) is a mutant strain of GAS within the emm1 family that was discovered in 2019 but has been in circulation since 2010. The strain differs by just 27 mutations when compared with other emm1 family strains which allows it to increase the production of streptococcal pyrogenic exotoxin A (SpeA) by more than nine-times. This makes the strain fitter and more dominant in the society. It was designated as the largest single contributor to both non-invasive and invasive infections in 2016.