Rapid expansion and international spread of M1 UK in the post-pandemic UK upsurge of Streptococcus pyogenes

The UK observed a marked increase in scarlet fever and invasive group A streptococcal infection in 2022 with severe outcomes in children and similar trends worldwide. Here we report lineage M1UK to be the dominant source of invasive infections in this upsurge. Compared with ancestral M1global strains, invasive M1UK strains exhibit reduced genomic diversity and fewer mutations in two-component regulator genes covRS. The emergence of M1UK is dated to 2008. Following a bottleneck coinciding with the COVID-19 pandemic, three emergent M1UK clades underwent rapid nationwide expansion, despite lack of detection in previous years. All M1UK isolates thus-far sequenced globally have a phylogenetic origin in the UK, with dispersal of the new clades in Europe. While waning immunity may promote streptococcal epidemics, the genetic features of M1UK point to a fitness advantage in pathogenicity, and a striking ability to persist through population bottlenecks

High variability of Panton-Valentine Leukocidine producing methicillin-resistant Staphylococcus aureus isolated from skin and soft tissue infections in the province of Bolzano

Introduction. Panton-Valentine leukocindin (PVL) positive community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates are widespread in many countries, with varying distribution and epidemiology. The aim of this study was to characterise the ten PVL positive MRSA isolates collected during February 2010 to January 2011 from skin and soft tissue infections in the North Italian Province of Bolzano. Methods. Accessory gene regulator (agr) typing, staphylococcal cassette chromosome (SCC) mec typing, spa typing,multi-locus sequence typing (MLST), toxin gene profiling, PCR for type I arginine catabolic mobile element (ACME) and antimicrobial resistance typing were applied to the isolates. Results. Eight different CA-MRSA clones were identified: ST30-IVc, ST772-V, ST80-IVc, ST5-IVc, ST88-IVa, ST93- IVa, ST8-IVc and the type I ACME positive ST8-IVa. Conclusions. The high heterogeneity of PVL-positive MRSA probably reflects the introduction of different clones by international travellers or immigrants