Streptococcus Pyogenes Bacteria Microbiology Lecture

In this slide, I will teach you about gram-positive cocci which streptococcus pyogenes. I will tell you about its diseases, transmission, pathogenesis, characteristics, lab diagnosis, treatment, and prevention in a short and easy way.

1. Streptococcus Pyogenes Group A Streptococcus

2. Gram Positive Streptococci Streptococcus Pyogenes (Group A Streptococci) Streptococcus Agalactiae (Group B Streptococci) Streptococcus Pneumoniae (Pneumococcus) Streptococcus Viridans (Streptococci Sanguis , Streptococci Mutans ) Enterococcus Faecalis

3. Diseases Suppurative Diseases (Local & Desseminated ) Non suppurative I mmunological diseases Toxigenic Infections

4. Local pyogenic infections Pharyngitis Sore throat ( Erethema & swelling of soft palate,uvula & posterior pharynx) Impetigo Crops of vesicles with honey colored crust Cellulitis , Erethema pain & swelling of lower layer of dorsal foot and other regions. Erysipelas , Well demarcated border of inflamed area on upper layer of skin. Nectrotizing Fasciitis ( Streptococcal gangrene ) D eath of parts of the body's soft tissue, Appear red/purple skin due lack of blood. Clostridum perfringens also cause it.

5. Desseminated pyogenic inFections Sepsis Sub acute bacterial endocarditis , Vegetation (abnormal growth )on mitral valve. Viridans most commonly.

6. Immune mediated, Post steptoccocal , non suppurative Rheumatic fever ( Pharyngitis, Mitral valve stenosis ,) JONES crtieria Poly arthritis, Heart disease , Sub cutaneous nodules, Erythema Marginatum , Sydenham chorea Glomerulonephritis ( Facial edema, Cola color urine)

7. Toxigenic infections Scarlet fever (Strawberry tongue, Pharyngitis, Different rash (swollen, iritative and pain) Toxic shock syndrome Systemic symptoms

8. Habitat & Transmission Habitat Throat & skin Transmission Respiratory Droplets ( small aqueous droplet produced by exhalation, consisting of saliva or mucus)

9. Enzymes involved in pathogenesis Hyaluronidase Breakdown a substance,“Spreading factor” mediates sub cutaneous spread in celluitits and other Suppurative infection Streptokinsase ( Fibrinolysin ) Plasminogen to plasmin, dissolve clot ,thrombi & emboli. Dnase ( Streptodornase ) Degrades DNA in exudates or necrotic tissue by immune reaction. IGA degrading enzyme Protease that cleave the IGA heavy chain.

10. Immunological Pathogenesis Antibody against component of bacteria for Non suppurative diseases. M protein impedes phagocytosis. Virulence factor which is rheumatogenic and nephritogenic . Rheumatic fever, Immunological cross reaction b/w bacterial antigen and heart and joint tissue Antibody against Streptococcal M protein react with myosin in cardiac tissue. Acute glomerulonephritis, Immune complexes b/w Streptoccocal antigen and antibody of those antigens trapped by glomeruli membrane. Activate complement,neutrophil attracted to site by C5a Protease produced by neutrophils damage glomeruli.

11. Toxins & hemolysins Erythrogenic toxin Superantigen cause rash of scarlet fever . Pyrogenic exotoxin A, ( Superantigen A & C) cause Toxic shock syndrome . Exotoxin B, Protease rapidly destroy tissue cause Flesh eating streptococci cause nectrotizing fasciitis . Streptolysin O Hemolysin which is oxygen labile, inactivated by oxidation. Anti streptolysin O antibody in rheumatic fever. Streptolysin S Hemolysin which is oxygen stable, not inactivated by oxidation.Form B hemolytic colonies.

12. Characteristics Gram positive cocci in chains B hemolytic colonies Antigenicity of cell wall carbohydrate Encapsulated Complete breakdown of RBCs. Hemolysis due Streptolysin O & S Lancefield classification group A (total A to U)

13. General a hemolysis, Green zone due biliverdin , I ncomplete lysis of RBCs in agar. b hemolytic, Clear zone due hemolysin enzyme O & S, C omplete lysis of RBCs Gamma hemolytic , No lysis of RBCs. C carbohydrate , Antigen on cell wall determine B hemolytic streptococci. Differentiate b/w Group A & B

14. Laboratory Diagnosis Gram stain smear & culture, For Suppurative infections (not useful) Blood agar , B hemolytic colonies from throat swab with patient sore throat. Catalase negative (H2O2 into H2O and O2) all Bacitracin sensitive, ( Inhibition growth) ELISA, Enzyme linked immunosorbent assay, for group A Steptococcal antigens in throat swabs not antibody. ASO i.e anti streptolysin O antibody titer for detection rheumatic fever prevous exposure. Antibody to streptococcal Dnase B for acute glomerulonephritis and prevous skin infections i.e impetigo.

15. Treatment Pencillin G ( No significant resistance) A moxicillin   ( Drug of choice) Azithromycin and clarithromycin ( Resistance in some communities)

16. Prevention Pencillin for rheumatic fever and recuurent pharyngitis Prevent damage to heart valve. Handwashing No vaccine

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