AUTHOR=Pinho Marcos D. , Foster Geoffrey , Pomba Constança , Machado Miguel P. , Baily Johanna L. , Kuiken Thijs , Melo-Cristino José , Ramirez Mário ,  The Portuguese Group for the Study of Streptococcal Infections , Vaz Teresa , Gião Marília , Ferreira Rui , Cristina Silva Ana , Costa Hermínia , Fátima Silva Maria , Amélia Afonso Maria , Domingos Ana , Marrão Gina , Grossinho José , Lopes Paulo , Lameirão Angelina , Abreu Gabriela , Selaru Aurélia , Marques Hermínia , Tomaz Margarida , Mota Paula , Helena Ramos Maria , Paula Castro Ana , Fonseca Fernando , Canhoto Nuno , Afonso Teresa , Pina Teresa , Peres Helena , Chantre Odete , Marques Joã , Marcelo Cristina , Peres Isabel , Lourenço Isabel , Pinto Margarida , Monteiro Lurdes , Marques Lito Luís , Toscano Cristina , Ana Pessanha Maria , Ramalheira Elmano , Diaz Raquel , Ferreira Sónia , Cravo Roxo Inês , Paula Castro Ana , Ribeiro Graça , Tomé Rui , Pontes Celeste , Boaventura Luísa , Chaves Catarina , Reis Teresa , Buschy Fonseca Ana , Ribeiro Manuela , Gonçalves Helena , Faustino Alberta , Alves Adelaide , Cármen Iglesias Maria , Fontes Ilse , Martinho Paulo , Luísa Gonçalves Olga Neto Maria , Sancho Luísa , Coutinho Adriana , Diogo José , Rodrigues Ana , Antónia Read Valquíria Alves Margarida Monteiro Maria , Bento Rosa 

TITLE=Streptococcus canis Are a Single Population Infecting Multiple Animal Hosts Despite the Diversity of the Universally Present M-Like Protein SCM

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00631

DOI=10.3389/fmicb.2019.00631

ISSN=1664-302X

ABSTRACT=<p><italic>Streptococcus canis</italic> is an animal pathogen which occasionally causes infections in humans. The <italic>S. canis</italic> M-like protein (SCM) encoded by the <italic>scm</italic> gene, is its best characterized virulence factor but previous studies suggested it could be absent in a substantial fraction of isolates. We studied the distribution and variability of the <italic>scm</italic> gene in 188 <italic>S. canis</italic> isolates recovered from companion animals (<italic>n</italic> = 152), wild animal species (<italic>n</italic> = 20), and humans (<italic>n</italic> = 14). Multilocus sequence typing, including the first characterization of wildlife isolates, showed that the same lineages are present in all animal hosts, raising the possibility of extensive circulation between species. Whole-genome analysis revealed that <italic>emm</italic>-like genes found previously in <italic>S. canis</italic> correspond to divergent <italic>scm</italic> genes, indicating that what was previously believed to correspond to two genes is in fact the same <italic>scm</italic> locus. We designed primers allowing for the first time the successful amplification of the <italic>scm</italic> gene in all isolates. Analysis of the <italic>scm</italic> sequences identified 12 distinct types, which could be divided into two clusters: group I (76%, <italic>n</italic> = 142) and group II (24%, <italic>n</italic> = 46) sharing little sequence similarity. The predicted group I SCM showed extensive similarity with each other outside of the <italic>N</italic>-terminal hypervariable region and a conserved IgG binding domain. This domain was absent from group II SCM variants found in isolates previously thought to lack the <italic>scm</italic> gene, which also showed greater amino acid variability. Further studies are necessary to elucidate the possible host interacting partners of the group II SCM variants and their role in virulence.</p>