Emerging Invasive Group A Streptococcus M1_UK Lineage Detected by Allele-Specific PCR, England, 20201

Abstract

Increasing reports of invasive Streptococcus pyogenes infections mandate surveillance for toxigenic lineage M1 UK . An allele-specific PCR was developed to distinguish M1 UK from other emm 1 strains. The M1 UK lineage represented 91% of invasive emm 1 isolates in England in 2020. Allele-specific PCR will permit surveillance for M1 UK without need for genome sequencing.

Insights gained from sequencing Australian non-invasive and invasive Streptococcus pyogenes isolates

“…The oldest known M1 UK isolates were collected in the UK in 2010 [19]. By 2013, M1 UK was the UK's most commonly sequenced emm1 clone [19,68]. Recently, Davies et al [66] showed that 50-75 % of sequenced emm1 isolates in Victoria and Queensland during 2017-2020 were M1 UK strains, and that it has been present in Australia since at least 2013.…”

Characterization of emergent toxigenic M1UK Streptococcus pyogenes and associated sublineages

“…M1 UK is now the dominant S. pyogenes emm 1 lineage in the UK, having expanded during an earlier upsurge in scarlet fever in 2014–2016 [4, 5]. Importantly, emm 1 strains are inherently virulent and represent the single most frequent emm type causing invasive infections in the UK [31, 32].…”

Tricontinental detection of Streptococcus pyogenes M1UK: A call for wider research and active surveillance

“…The M1UK lineage has also been identified elsewhere in Europe (5), North America (6, 7), and most recently in Australia, in isolates from Queensland and Victoria dating from 2013 (8), just 3 years after its first detection in England (3). While M1UK represented ~60% of Australian emm1 isolates by 2020, in England, this proportion reached 91% by 2020 (4,8). The detection of M1UK in Australia, including Queensland, underlines the ability of this lineage to spread in temperate and more tropical climates.…”

“…Despite the M123SNP sublineage being able to produce SpeA at a level that is indistinguishable from M1UK isolates (9), it has been fully outcompeted by M1UK in England (4). Although increased SpeA production is predicted to perpetuate community transmission, the fitness advantage(s) of M1UK may yet require additional features that promote emm1 survival in the human population, underlining a need for further research and surveillance.…”

“…Emm1 S. pyogenes strains are known to be inherently invasive and normally account for one quarter of invasive infections; currently however, emm1 isolates account for over half of invasive infections, rising to over 60% in children in England (2). The population of emm1 S. pyogenes isolates in England is dominated by a novel sublineage, M1UK, that has an intrinsic ability to express the phageencoded superantigenic toxin, streptococcal pyrogenic exotoxin (Spe) A (3,4). M1UK strains can be differentiated from strains belonging to the highly successful emm1 S. pyogenes globallydisseminated clone that emerged in the 1980's (M1global) by just 27 single nucleotide polymorphisms in the core genome (3).…”