Detection of toxigenic M1_UK lineage group A Streptococcus clones in Taiwan

Background: A new sublineage of emm1 group A Streptococcus (GAS), M1_UK, has emerged in Europe, North America, and Australia. Notably, a significant portion of emm1 isolates in Asia, particularly in Hong Kong and mainland China, acquired scarlet fever-associated prophages following the 2011 Hong Kong scarlet fever outbreak. However, the presence of the M1_UK sublineage has not yet been detected in Asia. Methods: This study included 181 GAS isolates (2011–2021). The emm type of these isolates were determined, and 21 emm1 isolates from blood or pleural fluid (2011–2021) and 10 emm1 isolates from throat swabs (2016–2018) underwent analysis. The presence of the scarlet fever-associated prophages and the specific single nucleotide polymorphisms of the M1_UK clone were determined by polymerase chain reaction and the genome sequencing. Results: The M1_UK lineage strains from throat swab and blood samples were identified. One of the M1_UK strain in Taiwan carried the scarlet fever-associated prophage and therefore acquired the ssa, speC, and spd1 toxin repertoire. Nonetheless, the increase of M1_UK was not observed until 2021, and there was a reduction in the diversity of emm types in 2020–2021, possibly due to the COVID-19 pandemic restriction policies in Taiwan. Conclusions: Our results suggested that the M1_UK lineage clone has introduced in Taiwan. In Taiwan, the COVID-19 restrictions were officially released in March 2023; therefore, it would be crucial to continuously monitor the M1_UK expansion and its related diseases in the post COVID-19 era.