For this study, whole genome sequencing of all clinical isolates (invasive and non-invasive) was performed by the UKHSA reference laboratory using the Illumina NextSeq 1000 platform with 100 base paired-end chemistry. Reads were trimmed to remove adaptor sequences and low-quality bases with Trimmomatic v0.3947 (link). Contamination was assessed based on Kraken248 (link) classification of reads mapped against a standard database for bacteria. Genomes with less than 90% of the reads mapped against S. pyogenes were excluded. Draught genomes were generated using SPAdes v3.15.449 (link). The assembly quality was assessed using QUAST v5.0.244 (link), and poor assemblies were filtered out if the genome size was higher than 2.1 Mbp and/or had more than 400 contigs. Genome annotation was performed with prokka v1.14.646 (link).
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