streptococcus pyogenes

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Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular, and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause Group A streptococcal infection. S. pyogenes is the predominant species harboring the Lancefield group A antigen, and is often called group A Streptococcus (GAS). However, both Streptococcus dysgalactiae and the Streptococcus anginosus group can possess group A antigen as well. Group A streptococci, when grown on blood agar, typically produce small (2–3 mm) zones of beta-hemolysis, a complete destruction of red blood cells. The name group A (beta-hemolytic) Streptococcus (GABHS) is thus also used.

The species name is derived from Greek words meaning ‘a chain’ (streptos) of berries (coccus [Latinized from kokkos]) and pus (pyo)-forming (genes), since a number of infections caused by the bacterium produce pus. The main criterion for differentiation between Staphylococcus spp. and Streptococcus spp. is the catalase test. Staphylococci are catalase positive whereas streptococci are catalase-negative. S. pyogenes can be cultured on fresh blood agar plates. Under ideal conditions, it has an incubation period of 1 to 3 days.

 

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streptococcus pyogenes
  1. Dr Md shahriar kabir B H M S; MPH
    Dr Md shahriar kabir B H M S; MPH Enlightened dr.basuriwala

    Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, butRead more

    Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause Group A streptococcal infection. S. pyogenes can cause a variety of diseases such as streptococcal:
    1. Pharyngitis,
    2. Rheumatic fever,
    3. Rheumatic heart disease, and
    4. Scarlet fever.

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streptococcus pyogenes
  1. Dr Md shahriar kabir B H M S; MPH
    Dr Md shahriar kabir B H M S; MPH Enlightened dr.basuriwala

    Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, butRead more

    Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause Group A streptococcal infection. S. pyogenes can cause a variety of diseases such as streptococcal pharyngitis, rheumatic fever, rheumatic heart disease, and scarlet fever.

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streptococcus pyogenes
  1. Dr Md shahriar kabir B H M S; MPH
    Dr Md shahriar kabir B H M S; MPH Enlightened dr.basuriwala

    Streptococcus pyogenes is a Gram-positive bacterium. It is a round-shaped coccus that is arranged in chains.

    Streptococcus pyogenes is a Gram-positive bacterium. It is a round-shaped coccus that is arranged in chains.

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streptococcus pyogenes
  1. Dr Md shahriar kabir B H M S; MPH
    Dr Md shahriar kabir B H M S; MPH Enlightened dr.basuriwala

    Streptococcus pyogenes is an aerobe and facultative anaerobe that grows best at an optimum temperature of 37°C and an optimum pH of 7.2. It requires enriched media for growth, such as blood agar, where it produces small (0.5-1mm), circular, semi-transparent colonies that produce a wide zone of β-hemRead more

    Streptococcus pyogenes is an aerobe and facultative anaerobe that grows best at an optimum temperature of 37°C and an optimum pH of 7.2. It requires enriched media for growth, such as blood agar, where it produces small (0.5-1mm), circular, semi-transparent colonies that produce a wide zone of β-hemolysis. Growth and hemolysis are promoted by 5-10% CO2. Virulent strains, on fresh isolation form lesions, and produce a ‘matt’ (finely granular) colony while avirulent strains form ‘glossy’ colonies.

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streptococcus pyogenes
  1. Dr Md shahriar kabir B H M S; MPH
    Dr Md shahriar kabir B H M S; MPH Enlightened dr.basuriwala

    Streptococcus pyogenes is a Gram-positive bacterium. This means that it retains the crystal violet stain used in the Gram staining procedure, and appears purple or blue under a microscope.

    Streptococcus pyogenes is a Gram-positive bacterium. This means that it retains the crystal violet stain used in the Gram staining procedure, and appears purple or blue under a microscope.

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enzymesstreptococcus pyogenes
  1. Dr Md shahriar kabir B H M S; MPH
    Dr Md shahriar kabir B H M S; MPH Enlightened dr.basuriwala

    1. Streptokinase (Ska) is a single-chain 414 amino acid protein, secreted by group A, C, and G streptococci. 2. The cysteine proteinase, SpeB, is also known as streptococcal pyrogenic erythrogenic toxin B or streptococcal cysteine proteinase. 3. Cell envelope proteinase. 4. Streptococcus secreted esRead more

    1. Streptokinase (Ska) is a single-chain 414 amino acid protein, secreted by group A, C, and G streptococci.
    2. The cysteine proteinase, SpeB, is also known as streptococcal pyrogenic erythrogenic toxin B or streptococcal cysteine proteinase.
    3. Cell envelope proteinase.
    4. Streptococcus secreted esterase, SsE, is an extracellular product that appears to have a role in virulence and pathogenesis, being essential for invasive infections and systemic dissemination.
    5. Streptococcus pyogenes secretes two well-known hemolysins, streptolysin O and streptolysin S, which have effects on a variety of cell types.
    6. Streptolysin O (SLO) is a pore-forming, cholesterol-dependent, oxygen-labile, thiol-activated cytotoxin. Similar types of hemolysins are produced by a variety of other pathogens, and the structure of SLO is similar to these other cholesterol-dependent cytolysins, but there are also some differences.
    7. Streptolysin S, SLS, is the second type of hemolysin produced by S. pyogenes, and was originally extracted from streptococcal cells grown in the presence of serum, hence its name. It is a member of a family of proteins known as the thiazole/oxazole-modified microcins, which are produced by a number of pathogens that show hemolytic exotoxin activity.
    8. The CAMP factor appears to be widespread among the streptococci, as it is present in groups A, B, C, G, M, P, R, and U.
    9. S. pyogenes is known to produce up to four DNases as extracellular products. A potent DNase produced by the M1T1 globally disseminated clone is the bacteriophage-encoded SdaD2, and the major DNase that contributes to virulence.
    10. S. pyogenes encodes proteins that are classified as hyaluronidases. These include the chromosomally-encoded hyaluronate lyase, HylA, and the bacteriophage-encoded hyaluronidases, HylP ; these phage-encoded enzymes are also hyaluronate lyases.
    11. Chromosomally encoded hyaluronate lyase.
    12. Bacteriophage-encoded hyaluronate lyase.
    13. Streptococcal inhibitor of complement (SIC) is a 31 kDa protein found in M1 strains of S. pyogenes.
    14. S. pyogenes produces a metalloprotein, superoxide dismutase (SodA), the function of which is to convert superoxide anions to oxygen and hydrogen peroxide; the hydrogen peroxide can then be detoxified by peroxidases.
    15. S. pyogenes encodes a number of surface-associated, immunoglobulin-binding proteins, including M proteins, M-related proteins, and M-like proteins.
    16. The immunoglobulin-degrading enzyme of S. pyogenes, IdeS, is a secreted cysteine proteinase that specifically cleaves the hinge region of IgG.
    17. EndoS (endo-β-N-acetylglucosaminidase) EndoS is a large (108 kDa) endoglycosidase Ig-degrading enzyme that removes carbohydrates from immunoglobulin G in a highly specific manner.
    18. Soluble M protein, M protein is a surface protein of group A streptococci, although it can be released through the action of bacterial- or host-derived proteases and can influence streptococcal virulence in that extracellular state.

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streptococcus pyogenestoxins
  1. Dr Md shahriar kabir B H M S; MPH
    Dr Md shahriar kabir B H M S; MPH Enlightened dr.basuriwala

    Few of the cellular components of group A streptococci appear to be directly toxic for animals or humans. Some preparations of M protein produce an immunotoxic effect on human platelets and neutrophils. Cell wall fragments produce a chronic multinodular inflammatory lesion of dermal connective tissuRead more

    Few of the cellular components of group A streptococci appear to be directly toxic for animals or humans. Some preparations of M protein produce an immunotoxic effect on human platelets and neutrophils. Cell wall fragments produce a chronic multinodular inflammatory lesion of dermal connective tissue. The peptidoglycan component of cell walls has many of the biological features of endotoxins. The exotoxins of group A streptococci include the erythrogenic toxins (pyrogenic exotoxins) and the cytolytic toxins (streptolysins S and O). The high prevalence of erythrogenic, toxin-producing strains is difficult to reconcile with the epidemiologic behavior of scarlet fever; the variations may be due to quantitative differences in toxin production or to a shift from the early scarlet fever-associated strains that produce A toxin to the currently prevalent strains that produce B and C toxins. Experiments with animals suggest that a positive Dick test and the rash of scarlet fever result not from a direct toxic effect but rather from enhancement by pyrogenic exotoxin(s) of acquired hypersensitivity to diverse streptococcal products. The mechanism of toxigenic phage conversion is not clear. The pyrogenic exotoxins are associated with the enhancement of endotoxin shock and a wide variety of other biologic properties. Streptolysin S is a nonantigenic polypeptide associated with various stabilizing carrier molecules. It lyses a wide range of mammalian cells, influences T lymphocyte functions, and is probably responsible for the leukotoxic property of group A streptococci. Rheumatic fever has been associated with a streptococcal outbreak due to a nonhemolytic (streptolysin S-negative) strain. Streptolysin O is an oxygen-labile (thiol-activated) cytolysin. It is inhibited by nonesterified cholesterol and binds to cholesterol in the membranes of mammalian cells and organelles, an interaction producing ring-like and C-shaped structures demonstrable by electron microscopy. Streptolysin O affects a number of leukocyte functions. It produces profound electrocardiographic changes in experimental animals and toxic effects on pulsating heart cells in tissue culture. The observation that rheumatic fever is not associated with infection of the skin due to group A streptococci has suggested that nonesterified cholesterol in the epidermis may inhibit a toxic effect of streptolysin O, an effect necessary for the development of rheumatic fever.

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