The Emergence and Impact of the M1UK Lineage on Invasive Group A Streptococcus Disease in Aotearoa New Zealand

Abstract

M1_UK is associated with current surges in invasive infection globally, partly due to increased production of superantigen streptococcal pyrogenic exotoxin A. We show that M1_UK is now the dominant invasive emm1 lineage in Aotearoa New Zealand and is genomically related to community infections, suggesting that measures that effectively prevent group A Streptococcus pharyngitis in children could reduce invasive disease.

Keywords: M1UK; emm1; group A streptococcus; invasive group A streptococcal disease.

Figure 1.

A, Proportion of emm1 lineages: M1_global and M1_intermediate combined (blue) and M1_UK (red) as a proportion of all passive surveillance invasive emm1 isolates from New Zealand collected from patients by year (January 2013–November 2023). All M1_intermediate strains in this study are the M1_13SNPs sublineage (Supplementary Data 1). B, Maximum likelihood phylogeny of 377 New Zealand invasive group A streptococcal isolates, 539 global context isolates [3], and 59 community emm1 isolates from Auckland school-aged children [6]. Terminal nodes are colored by location, and the outer ring indicates emm1 lineage. The inner ring shows invasive and community isolates from the Auckland 2018–2019 subset. Scale bar: number of substitutions per site. C, Anti-SpeA antibody responses in sera from children with pharyngitis (M1_UK, n = 13; M1_global, n = 23; non-emm1, n = 15) vs healthy controls (n = 23). The non-emm1 group combines data from children with emm81 (open diamonds) and emm53 (closed diamonds) pharyngitis. Horizontal lines show median values. Statistical significance was assessed by the Kruskal-Wallis test with Dunn test for multiple comparisons. ***P < .001. ****P < .0001. MFI, mean fluorescence intensity.