TABLE 2.

Streptococci virulence factors involved in biofilm formation.

Protein	Function and/or substrate	Species	References
Adhesion protein - AdcA	Cell adhesion; Zinc ion transport – Contributes to the infection process	S. pyogenes, SDSE, SDSD, SESZ, S. pneumoniae, S. canis, S. agalactiae	Moulin et al., 2016; Cao et al., 2018
Collagen-like protein 1 (scl-1)	Promotes adhesion and biofilm formation, decreases bacterial killing by neutrophil extracellular traps	S. pyogenes, S. agalactiae, S. pneumoniae, and S. equi.	Oliver-Kozup et al., 2011; Döhrmann et al., 2014; Lukomski et al., 2017
Collagen-like protein SclB (sclB)		S. pyogenes, S. uberis, SDSE, SDSD, S. agalactiae, S. pneumoniae, and S. equi.	Rato et al., 2011; Lukomski et al., 2017
FbaA	Fibronectin and laminin-binding protein	S. pyogenes; S. parasanguinis	Chen et al., 2020
FbaB/PFBP/PrtF2	Fibronectin and laminin-binding protein	S. pyogenes	Rohde et al., 2011; Brouwer et al., 2016; Šmitran et al., 2016
Fbp54	Fibronectin and fibrinogen-binding protein	S. pyogenes	Raynes et al., 2018
FbsA, FbsB	Fibronectin and fibrinogen-binding protein	S. agalactiae	Rosenau et al., 2007
FnbA, FnbB	Fibronectin-binding proteins	SDSD; SDSE	O’Neill et al., 2009; Alves-Barroco et al., 2018
GfbA	Fibronectin-binding proteins	SDSE	Lindgren et al., 1994; Oppegaard et al., 2018
Glyceraldehyde-3-phosphate dehydrogenase (plr)	Plasmin and Fn-binding protein	S. pyogenes, SDSE, SDSD, S. suis, S. agalactiae, S. uberis	Seifert et al., 2003; Rato et al., 2011; Reinoso, 2017
Hyaluronic acid (HA) capsule	Immune evasion upon colonization of host tissues; adhesion to the surface of the host cell	S. pyogenes	Falaleeva et al., 2014; Vyas et al., 2019
Laminin-binding protein (lmb)	Laminin-binding surface proteins	S. pyogenes, SDSE, SDSD, SESZ, S. pneumoniae, S. canis, S. agalactiae	Al Safadi et al., 2010; Rato et al., 2011
Lipoteichoic acid (LTA)	Adherence to epithelial cells of host Biofilm formation	S. pyogenes, S. uberis, SDSE, SDSD, S. agalactiae, S. pneumoniae, and S. equi, S. gordonii	Courtney et al., 2009; Rato et al., 2011; Shiraishi et al., 2016; Lima et al., 2019
M protein (emm)	Adherence to epithelial cells of host; Plasminogen, fibronectin and Fibrinogen-binding proteins; Ig-binding proteins	S. pyogenes, SDSE, SDSD, SDSZ, S. canis	Courtney et al., 2009; Rato et al., 2011; McNeilly and McMillan, 2014; Frost et al., 2018
M-like protein (enn) complexe
Pili, fimbriae, fibrils	Biofilm formation Coaggregation, biofilm formation, phagocyte resistance; multiple substrates	S. pyogenes, S. agalactiae, SDSE, S. pneumoniae	Manetti et al., 2007; Proft and Baker, 2009; Rajagopal, 2009; Konto-Ghiorghi et al., 2009; Genteluci et al., 2015; Ma et al., 2017
R28	Promotes adhesion to host cells via direct binding to integrins	S. pyogenes, SDSE, SDSD	Rato et al., 2011; Weckel et al., 2018; Eraso et al., 2020
SfbI/PrtF1	Fibronectin-binding proteins; Ig-binding protein	S. pyogenes	Šmitran et al., 2016
SfbX	Fibronectin-binding proteins	S. pyogenes	Brouwer et al., 2016; Šmitran et al., 2016
HtrA	Serine protease; Degrades proteins in response to stress; bility to adhere to the extracellular matrix that enable adhesion to host tissues	S. pneumoniae, S. pyogenes, SDSD, SDSE	Lyon and Caparon, 2004; Kim and Kim, 2005
speB	Targets several different host proteins, namely interleukins, antimicrobial peptides, and components of the extracellular matrix	S. pyogenes	Doern et al., 2009; Roberts et al., 2010a; Connolly et al., 2011; Carothers et al., 2020
DNases	Degradation of NETs that are produced by the host’s immune system cells (like neutrophils)	S. pyogenes, S. agalactiae, SDSD, SDSE	Rato et al., 2010, 2011; Genteluci et al., 2015; Remmington and Turner, 2018
Biofilm regulatory proteins A BrpA	Biofilm formation, autolysis, and cell division	S. pyogenes, S. agalactiae, S. mutans, SDSD, SDSE	Bitoun et al., 2012, 2014; Alves-Barroco et al., 2018; Patras et al., 2018