Novel emm4 lineage associated with an upsurge in invasive group A streptococcal disease in the Netherlands, 2022
Boas C.L. van der Putten, Wendy C.M. Bril-Keijzers, Lidewij W. Rümke, Stefan M.T. Vestjens, Linda A.M. Koster, Marloes Willemsen, Marlies A. van Houten, Nynke Y. Rots, Bart J. M. Vlaminckx, Brechje de Gier, Nina M. van Sorge
Abstract
Invasive group A streptococcal (iGAS) disease cases increased in the first half of 2022 in the Netherlands, with a remarkably high proportion of emm 4 isolates. Whole-genome sequence analysis of 66 emm 4 isolates, 40 isolates from the pre-coronavirus disease 2019 (COVID-19) pandemic period 2009–2019 and 26 contemporary isolates from 2022, identified a novel Streptococcus pyogenes lineage (M4 NL22 ), which accounted for 85 % of emm 4 iGAS cases in 2022. Surprisingly, we detected few isolates of the emm 4 hypervirulent clone, which has replaced nearly all other emm 4 in the USA and the UK. M4 NL22 displayed genetic differences compared to other emm 4 strains, although these were of unclear biological significance. In publicly available data, we identified a single Norwegian isolate belonging to M4 NL22 , which was sampled after the isolates from this study, possibly suggesting export of M4 NL22 to Norway. In conclusion, our study identified a novel S. pyogenes emm 4 lineage underlying an increase of iGAS disease in early 2022 in the Netherlands and the results have been promptly communicated to public health officials.