Emergence of clade 3 emm89 group A Streptococcus in Queensland, Australia

The emergence of a new clade of emm89 group A Streptococcus (GAS) (clade 3) has been described in several countries. Strains in this clade have been reported to have genomic characteristics that lead to increased expression of virulence factors and may confer a selective advantage over previous emm89 strains. To investigate whether clade 3 GAS is present in the emm89 GAS population of Queensland, Australia, all emm89 GAS isolates received by the Queensland Public Health Microbiology Reference Laboratory since emm typing began in the early 2000s underwent genomic sequencing and analysis. Analysis of sequences from 293 emm89 GAS isolates demonstrated the presence of distinct genomic groups in the Queensland emm89 GAS population. Unlike emm89 GAS populations described in the UK and USA, which were mostly ST101 and ST407, there were a relatively high number of ST142 and ST812 strains in the Queensland emm89 GAS population. However, the majority of Queensland isolates belonged to clade 3, with 80% (n=233) of emm89 GAS isolated from 2006 onwards belonging to this clade. All Queensland clade 3 isolates had the reported genomic features associated with higher virulence potential including increased streptolysin O production and an acapsular phenotype. Clade 3, which has emerged to become the dominant clade of emm89 GAS in Europe and the USA, is now also the dominant clade in Queensland.