Pharyngitis, Part 3; Virulence factors of Streptococcus pyogenes | streptococcus pyogenes ก่อโรค

Pharyngitis, Part 3; Virulence factors of Streptococcus pyogenes


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This is the third video on pharyngitis and is focusing on the Virulence factors of Streptococcus pyogenes. The link to the 1st two videos are:
1. Part 1: https://youtu.be/2wC1Deha6Hs
2. Part 2: https://youtu.be/Jv7Nmed6msI
S. pyogenes has several virulence factors that enable it to attach to host tissues, evade the immune response, and spread by penetrating host tissue layers.
1. Bacterial capsule
A carbohydratebased bacterial capsule composed of hyaluronic acid surrounds the bacterium, protecting it from phagocytosis by neutrophils. Glycoprotein molecules known as endocytic pattern recognition receptors are found on the surface of phagocytes. They are so named because they recognize and bind to pathogenassociated molecular patterns components of common molecules such as peptidoglycan, teichoic acids, lipopolysaccharides, mannans, and glucans, found in many microorganisms. The capsule can cover up these surface molecules preventing their attachment to endocytic pattern recognition receptors on phagocytes
2. Lipoteichoic acid (LTA): A major hydrophobic component of the cell surface that contributes to adhesion to the host cell.
3. M protein helps in the attachment to pharyngeal mucosa, is strongly antiphagocytic, and is the major virulence factor for S. pyogenes. It binds to serum factor H [A regulator of complement activation], destroying C3 convertase [It catalyzes the proteolytic cleavage of C3 protein into C3a and C3b (hence the name \”C3convertase). The smaller fragment called C3a serves to increase vascular permeability and promote extravasation of phagocytes, while the larger C3b fragment can be used as an opsonin] and preventing opsonization by C3b. However, plasma B cells can generate antibodies against M protein which will help in opsonization and further the destruction of the microorganism by the macrophages and neutrophils. Crossreactivity of antiM protein antibodies with heart muscle has been suggested to be associated in some way with rheumatic fever.
4. Streptococcus pyogenes fibronectinbinding proteins
S. pyogenes can invade host epithelial cells via their own fibronectin (Fn)binding protein. Its binds to fibronectin and form a bridge to a5b1integrins, which leads to rearrangement of cytoskeletal actin in host cells and uptake of invading bacteria.
1. Fibronectin: (~440kDa) glycoprotein of the extracellular matrix that binds to receptor integrins. 
Integrin can cluster with a number of molecules including Talin, Paxillin, (proteins), and focal adhesion kinase (protein) forming a cell membrane structure known as focal adhesion contact.
Stress fibers are usually composed of 1030
actin filaments and play an important role in
cellular contractility, providing force for a
number of functions such as cell adhesion,  migration, and morphogenesis
5. S. pyogenes produce an extracellular hyaluronidase (hyaluronate lyase) which may be associated with the spread of the organism during infection. This protein have 868 amino acid protein with a molecular size of 99,636 Da. This toxin cleaves the β1,4 bond between Nacetylglucosamine and dglucuronic acid, the repeating disaccharide that comprises the hyaluronic acid, causing local inflammation and enable bacteria to spread to the bloodstream
Functions of hyaluronic acid.
Connective tissue
Extracellular matrix
Angiogenesis
Migration
6. In the blood, S. pyogenes produces streptolysin O and S to causing hemolysis/ Red blood cells destruction
7. Erythrogenic toxins, also referred to as streptococcal pyrogenic exotoxins (Spe) are secreted by S. pyogenes. Spe are known to damage the plasma membranes of blood capillaries under the skin and produce a red skin rash (characteristic of scarlet fever) and there are three types of it
a. SpeA b. SpeB c. SpeC
The binding of SpeA and SpeB to the MHCII of the macrophages activates about 30% of the Tcell population which is about 300 times more powerful than the conventional antigens. This stimulates the release of a whole bunch of inflammatory cytokines which is known as the cytokine storm or hypercytokinemia. This is a physiological reaction in humans and other animals in which the innate immune system causes an uncontrolled and excessive release of cytokines. Normally, cytokines are part of the body’s immune response to infection, but their sudden release in large quantities can cause multisystem organ failure and death. This is because of toxic shock syndrome which causes widespread systemic vasodilation with a sharp drop in blood pressure that deprives organs of oxygen and can lead to death.
The S. pyogenes can colonize the skin, mucosa of the pharynx, vagina, and the rectum, in individuals with the normal immune system as the immune system keep it under control
It can be a problem in individuals with weak or immune system line infants and elderly people, immunecompromised individuals like those with HIV, diabetes, or malignancy.

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Pharyngitis, Part 3; Virulence factors of Streptococcus pyogenes

STREPTOCOCCAL PYOGENES-CLINICAL MANIFESTATIONS-MICROBIOLOGY LECTURES


STREPTOCOCCAL PYOGENES-CLINICAL MANIFESTATIONS-MICROBIOLOGY LECTURES

Streptococcus Pyogenes – Diseases and Their Management


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Streptococcus pyogenes caused diseases can be divided into the following categories:
Pyogenic or diseases due to direct tissue invasion by Streptococcus pyogenes.
Diseases mediated by the exotoxin.
And, diseases caused the immune complexes produced after the host’s immune response to the pathogen.
Pyogenic diseases are separated into:
Throat and skin infections.
Throat infection is the commonly known strep throat.
Strep throat causes about 7 million medical visits yearly in the US.
The second set of diseases are skin infections. These can be any of the following:
Folliculitis
Pyoderma/a pustule
Cellulitis
Erysipelas
Impetigo
Toxinmediated diseases are:
Scarlet fever
Toxic shocklike syndrome
Necrotizing fasciitis
Immunogenic diseases resulting from the antibody and antigen complexes depositing in various tissues. Or the pathogen antigens mimicking our normal proteins causing our immune system to attack our tissues.
Two diseases are important:
Rheumatic Fever
Poststreptococcal glomerulonephritis …
Disclaimer:
This video is not intended to provide assessment, diagnosis, treatment, or medical advice; it also does not constitute provision of healthcare services. The content provided in this video is for informational and educational purposes only.
Please consult with a physician or healthcare professional regarding any medical or mental health related diagnosis or treatment. No information in this video should ever be considered as a substitute for advice from a healthcare professional. …
Disclaimer:
This video is not intended to provide assessment, diagnosis, treatment, or medical advice; it also does not constitute provision of healthcare services. The content provided in this video is for informational and educational purposes only.
Please consult with a physician or healthcare professional regarding any medical or mental health related diagnosis or treatment. No information in this video should ever be considered as a substitute for advice from a healthcare professional.

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Streptococcus Pyogenes - Diseases and Their Management

Streptococcus pyogenes – GAS


Streptococcus pyogenes
Group A Beta Hemolytic Strep
Music by Danny Mood
Sources: will update this soon

Streptococcus pyogenes - GAS

Streptococcus Pyogenes | Visual Mnemonic | Microbiology |Bacteriology |


This video is a complete visual mnemonic on streptococcus Pyogenes for mbbs ug level microbiology.
It covers morphological features, media \u0026 colony characters, pathogenicity and treatment of strep. pyogenes
About meHi! I am a med student🇮🇳 \u0026 love to make videos to make a medico’s life easier that too in an organized manner, check out the playlists for more. Come let’s study together here at Made4Med. 😊
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Streptococcus Pyogenes | Visual Mnemonic | Microbiology |Bacteriology |

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