Detection of toxigenic M1_UK lineage group A Streptococcus clones in Taiwan

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.

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.

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.

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.