How many virulence factors does Streptococcus pyogenes have?
Virulence factors of group A streptococci include (1) M protein and lipoteichoic acid for attachment; (2) a hyaluronic acid capsule that inhibits phagocytosis; (3) other extracellular products, such as pyrogenic (erythrogenic) toxin, which causes the rash of scarlet fever; and (4) streptokinase, streptodornase (DNase B …
What toxins does Streptococcus pyogenes produce?
Erythrogenic toxins, also referred to as streptococcal pyrogenic exotoxins, are secreted by strains of the bacterium Streptococcus pyogenes. SpeA and speC are superantigens, which induce inflammation by nonspecifically activating T cells and stimulating the production of inflammatory cytokines.
How are toxins virulence factors?
Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response.
Which streptococci produce a number of virulence factors?
Streptococcus pyogenes possesses a wide variety of virulence factors and can cause severe invasive infections. Most S. pyogenes express surface-located fibronectin-binding proteins as major invasion molecules. We identified 2 novel fibronectin-binding proteins (FbaA and FbaB) in S.
Does Streptococcus pyogenes have a flagella?
One of the most common S. pyogenes strains is M1T1, which is responsible both for pharyngitis and more severe states, such as necrotizing fasciitis or toxic shock syndrome. This bacterium is equipped with flagella referred to as antigen T.
What are the virulence factors of Streptococcus agalactiae?
Table 1
| Virulence factor | Mode of action | Genetic basis |
|---|---|---|
| Sialic acid capsular polysaccharide (CPS) | Prevents recognition of GBS through molecular mimicry of host-cell surface glycoconjugates | cpsA–L, neuA–D |
| Masks pro-inflammatory cell wall components | ||
| Superoxide dismutase (SodA) | Detoxifies singlet oxygen and superoxide | soda |
Are Exoenzymes virulence factors?
Virulence factors contribute to a pathogen’s ability to cause disease. Exoenzymes and toxins allow pathogens to invade host tissue and cause tissue damage. Exoenzymes are classified according to the macromolecule they target and exotoxins are classified based on their mechanism of action.
What is the toxin for streptococcus?
The exotoxins of group A streptococci include the erythrogenic toxins (pyrogenic exotoxins) and the cytolytic toxins (streptolysins S and O).
Which are the virulence factors?
Virulence factors are bacteria-associated molecules that are required for a bacterium to cause disease while infecting eukaryotic hosts such as humans. A surprisingly large number of virulence factors are encoded by prophage infecting bacterial pathogens, such as cholera toxin, Shiga toxin, and diphtheria toxin.
What is the major virulence factor of Streptococcus pneumoniae?
1. Polysaccharide capsule: S. pneumoniae’s extracellular polysaccharide capsule, the most important virulence factor (55), helps to initiate infection by allowing the bacterium to adhere to host cells and cause inflammation, while also providing protection from the host’s immune system (54, 55).
Are Streptococcus pyogenes motile?
Streptococcus pyogenes Group A (β-hemolytic) streptococci (GAS), is an aerobic, gram-positive extracellular bacterium. It is made up of non-motile, non-sporing cocci that are less than 2 µm in length and that form chains and large colonies greater than 0.5 mm in size.
What are the toxins and superantigens of Group A streptococci?
Toxins and Superantigens of Group A Streptococci Streptococcus pyogenes (i.e., the group A Streptococcus) is a human-restricted and versatile bacterial pathogen that produces an impressive arsenal of both surface-expressed and secreted virulence factors.
How does a strep infection lead to toxic shock syndrome?
Any group A strep infection may progress to STSS. Disease occurs with entry of the bacterium through a compromised barrier (such as a skin injury) or through mucus membranes. The bacteria then spread to deep tissues and eventually to the bloodstream. The main sites of entry for streptococci leading to toxic shock syndrome include:
How does s.pyogene contribute to organ failure?
Massive cytokine cascades contribute to the development of shock or organ failure. S. pyogenes are gram-positive cocci that grow in chains (see Figure 1). They exhibit β -hemolysis (complete hemolysis) when grown on blood agar plates.
