{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T15:55:55Z","timestamp":1785426955704,"version":"3.56.0"},"reference-count":54,"publisher":"American Society for Microbiology","issue":"3","license":[{"start":{"date-parts":[[2026,3,10]],"date-time":"2026-03-10T00:00:00Z","timestamp":1773100800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,3,10]],"date-time":"2026-03-10T00:00:00Z","timestamp":1773100800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"DOI":"10.13039\/501100000024","name":"Canadian Institutes of Health Research","doi-asserted-by":"publisher","award":["Project Grant 461623"],"award-info":[{"award-number":["Project Grant 461623"]}],"id":[{"id":"10.13039\/501100000024","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000925","name":"National Health and Medical Research Council","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100000925","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001674","name":"Fondation Leducq","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001674","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Infect Immun"],"published-print":{"date-parts":[[2026,3,10]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      Multiple countries have observed an alarming increase in scarlet fever cases, and invasive infections often associated with a new sublineage of\n                      <jats:italic toggle=\"yes\">Streptococcus pyogenes<\/jats:italic>\n                      known as M1\n                      <jats:sub>UK<\/jats:sub>\n                      . M1\n                      <jats:sub>UK<\/jats:sub>\n                      strains express increased levels of the streptococcal pyrogenic exotoxin A (SpeA) superantigen, and here we compare the virulence characteristics of this sublineage with the circulating M1\n                      <jats:sub>global<\/jats:sub>\n                      strain. We obtained contemporary Canadian M1\n                      <jats:sub>UK<\/jats:sub>\n                      isolates, and genome sequencing revealed that some M1\n                      <jats:sub>UK<\/jats:sub>\n                      strains had acquired additional DNAse- and superantigen-encoding prophage elements, as well as an isolate with a mutation in\n                      <jats:italic toggle=\"yes\">covS<\/jats:italic>\n                      . Five\n                      <jats:italic toggle=\"yes\">S<\/jats:italic>\n                      .\n                      <jats:italic toggle=\"yes\">pyogenes<\/jats:italic>\n                      strains were chosen for functional experiments, including 5448 (M1\n                      <jats:sub>global<\/jats:sub>\n                      strain), M1\n                      <jats:sub>UK<\/jats:sub>\n                      350 (a \u201ctypical\u201d M1\n                      <jats:sub>UK<\/jats:sub>\n                      strain), M1\n                      <jats:sub>UK<\/jats:sub>\n                      162 (M1\n                      <jats:sub>UK<\/jats:sub>\n                      strain containing a mutation in the\n                      <jats:italic toggle=\"yes\">covS<\/jats:italic>\n                      gene), M1\n                      <jats:sub>UK<\/jats:sub>\n                      362\n                      <jats:sub>\u03a6SP1380.vir<\/jats:sub>\n                      (M1\n                      <jats:sub>UK<\/jats:sub>\n                      strain containing a prophage element encoding the\n                      <jats:italic toggle=\"yes\">spd1<\/jats:italic>\n                      ,\n                      <jats:italic toggle=\"yes\">speC<\/jats:italic>\n                      , and\n                      <jats:italic toggle=\"yes\">ssa<\/jats:italic>\n                      genes), and M1\n                      <jats:sub>UK<\/jats:sub>\n                      155\n                      <jats:sub>\u03a6370.1<\/jats:sub>\n                      (M1\n                      <jats:sub>UK<\/jats:sub>\n                      strain containing a prophage element encoding the\n                      <jats:italic toggle=\"yes\">spd1<\/jats:italic>\n                      and\n                      <jats:italic toggle=\"yes\">speC<\/jats:italic>\n                      genes). Exoprotein profiles demonstrated that all M1\n                      <jats:sub>UK<\/jats:sub>\n                      background strains had enhanced production of the SpeA superantigen relative to\n                      <jats:italic toggle=\"yes\">S. pyogenes<\/jats:italic>\n                      5448. Furthermore, strains that had acquired the additional prophage elements showed enhanced activation for human T cells, although cytotoxic activity, adhesion capacity, and DNA degradation were not detectably different. Using a \u201chumanized\u201d superantigen-sensitive HLA-transgenic mouse infection model, the M1\n                      <jats:sub>UK<\/jats:sub>\n                      162\n                      <jats:italic toggle=\"yes\">covS<\/jats:italic>\n                      mutant, and both M1\n                      <jats:sub>UK<\/jats:sub>\n                      362\n                      <jats:sub>\u03a6SP1380.vir<\/jats:sub>\n                      and M1\n                      <jats:sub>UK<\/jats:sub>\n                      155\n                      <jats:sub>\u03a6370.1<\/jats:sub>\n                      strains each demonstrated increased severity during experimental skin infection compared to 5448 and M1\n                      <jats:sub>UK<\/jats:sub>\n                      350. These findings indicate that circulating M1\n                      <jats:sub>UK<\/jats:sub>\n                      background strains continue to acquire additional prophage-encoded virulence factors, or hypervirulent\n                      <jats:italic toggle=\"yes\">covS<\/jats:italic>\n                      mutations, and that these genetic alterations may contribute to increase severity of human infections.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1128\/iai.00503-25","type":"journal-article","created":{"date-parts":[[2026,2,9]],"date-time":"2026-02-09T15:20:52Z","timestamp":1770650452000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Acquisition of toxin-encoding lysogenic bacteriophage elements enhances the virulence of pandemic\n                    <i>Streptococcus pyogenes<\/i>\n                    M1\n                    <sub>UK<\/sub>"],"prefix":"10.1128","volume":"94","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4652-4152","authenticated-orcid":false,"given":"Juan Manuel","family":"D\u00edaz","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02grkyz14","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Microbiology and Immunology, University of Western Ontario","place":["London, Canada"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-0046-6751","authenticated-orcid":false,"given":"Jasmine E. 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