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Streptococcus

Streptococcus. Hugh B. Fackrell Filename: Strept.ppt. Streptococcus Outline. Streptococcus Characteristics Streptococcal Diseases. Streptococcus: characteristics. Genus definition Growth requirements Capsule Colonial morphology Hemolysis Destruction of RBCs Hemolysins

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Streptococcus

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  1. Streptococcus Hugh B. Fackrell Filename:Strept.ppt

  2. Streptococcus Outline • Streptococcus Characteristics • Streptococcal Diseases

  3. Streptococcus: characteristics • Genus definition • Growth requirements • Capsule • Colonial morphology • Hemolysis • Destruction of RBCs • Hemolysins • molecules that destroy RBCs

  4. StreptococcusGenus Definition • Gram +ve cocci, chains or pairs • Catalase -ve facultative anaerobes • some strictly anaerobic • some capnophilic (CO2) • Ferment sugars to mixed acids and ethanol • Lancefield group D is motile

  5. Fastidious • Most Streptococci are fastidious in their growth requirements • Grow poorly on nutrient agar • Grow well on blood agar

  6. Capsule • Made of hyaluronic acid: • polymer of glucuronic acid & N-acetylglucosamine • Non immunogenic • hyaluronic acid intercellular cement • detected only in young(2-4 h) broth cultures • bacteria producehyaluronidase

  7. Glossy Mucoid Colonial Morphology • GLOSSY: no capsule, colonies small • MUCOID: capsule, colonies are large, glistening, viscous • MATT:capsule, older colonies are dried, flatter rougher

  8. Alpha Hemolysis Greening “viridans” Two Forms of Hemolysis Beta Hemolysis Clearing (Gamma hemolysis = no lysis)

  9. Streptococcal Beta Hemolysis • Two hemolysins • Both cause clearing • Both involved in disease

  10. Hemolysin S (stable in air) • Beta hemolysis on blood agar • Do not develop antibodies • Induces arthritis • Two parts • Carrier • hemolysin polypeptide • cell bound hemolysin • lyses leukocytes and platelets • stimulates release of lysosomal contents

  11. Subsurface colony of Streptococcus producing Hemolysin 0 Hemolysin O • Oxidized in air • oxygen labile (reversible) • Protein • Cardiotoxic • patients develop antibodies • ASOT • cholesterol labile (irreversible) • Antistreptolysin O test

  12. Pharyngitis Scarlet Fever Erysipalas ( St. Antony’s fire) Cellulitis Puerperal Fever Sepsis Meningitis Pneumonia Subacute Bacterial Endocardititis Otitis Media Streptococcus pyogenes Suppurative Diseases

  13. Pharyngitis: incubation period of 2 to 4 days sore throat, fever, malaise, headache Erythema of the pharynx cervical lymphadenopathy diagnosis -- differential -- viral pharyngitis Scarlet fever: all of the above plus red rash and red tongue Pyoderma Non-suppurative, inflammatory: Diseases of S. pyogenes

  14. Streptococcal Suppuration

  15. “Childbirth Fever” Semmelweis Membranes of genital tract ruptured fulminating septicemia fatal 24-48 hr S. pyogenes 60-75% of cases Anaerobic streptococci 20-25% S. pyogenes Not isolated from vagina of healthy females before birth 50-60% from physician rest from own nose & throat Puerperal Fever

  16. Post vaccination Streptococcal Infection

  17. Streptococcal Cellulitis

  18. Scarlet Fever

  19. Scarlet Fever Rash • Peticial hemorrhage • Pin point • Subcutaneous • Erythrogenic toxin • Scarletina toxin • causes rash • associated with a temperate phage

  20. Scarlet Fever Strawberry Tongue

  21. Schultz-Charlton test • Inject 0.1 ml antitoxin subcutaneously • Rash fades after 6-8 hours (possible delay 14 h) • Differentiates from other similar rashes

  22. Erysipalas • Secondary invasion • minor original lesion • Skin reddened thickened • later purple • Bacteria only in advancing edge

  23. Erysipalas: butterfly rash • Butterfly rash • common near nose • spreads after 4-6 days • Septicemia common complication • No toxin • No immunity • repeated attacks possible

  24. Rheumatic Fever • autoimmune • acute glomerulonephritis • Acute, non suppurative • post streptococcal inflammation • Joints, heart valves,myocardium,nerves • chorea- inflammation of nerves

  25. Scarred heart valves • reduced cardiac output • heart failure • Mitral valve stenosis • edema, hypertension, hematuria and proteinuria

  26. Scarred heart valves Rheumatic Endocarditis

  27. Rheumatic fever latent period • Latent period 2-4 weeks • same after repeated infections • not immunological • Antibiotics taken during first week of pharyngeal infection • Drop Steptococcal count • Block rheumatic fever

  28. Aschoff Bodies • Inflammation of myocardium • Mononuclear cell infiltration • Granuloma-like nodules • Characteristc of rheumatic fever

  29. Streptococcal Antigens • Lancefield groups • M antigens • T antigens • R antigens

  30. StreptococcusLancefield Groups • Rebecca Lancefield • Grouped by presence of distinctive cell wall antigens • Polysacchardies or glycero teichoic acids • Antigens labelled A-T • exclude I & J • Group A Streptococci Clinically Important

  31. Lancfield Groups • S. pneumoniae N/A • S.pyogenes -- Lancefield Group A • S.agalactiae -- Lancefield Group B • Enterococcus-Lancefield Group D • Viridans group

  32. Group A Streptococci • S. pyogenes Group A • clinically important • Lancefield grouping time consuming • Group A correlated with sensitivity to bacitracin Bacitracin sensitive Beta hemolytic Strept reported as Group A Strept

  33. glycerol teichoic acid -- associated with the cytoplasmic membrane Streptococcus bovis, Enterococcus faecalis, Enterococcus faecium resist bile and high concentrations of sodium chloride Disease: urinary tract infection intra-abdominal abcesses wound infection Endocarditis Group D Streptococci

  34. M antigens • proteins of the pilus • sensitive to Pepsin & Trypsin • soluble at pH 2 • 50 types • Involved in rheumatic fever • 5-8 types • Antibodies neutralize streptococcal infections

  35. Pathogenesis • capsule -- non-immunogenic • M Protein -- antiphagocytic, anticomplementary • Lipoteichoic acid (LTA): • mediates adherence to epithelial cells • LTA binding protein • Host cell membrane: • Deacylated LTA

  36. Enzymes • Streptokinase A & B: • lyse blood clots • DNA ase: • depolymerase DNA in pus • Hyaluronidase: • hyaluronic acid • DPN ase

  37. Lab diagnosis • Gram stain -- good in cases of pyoderma • fluorescent antibody • detection of antibodies to Streptolysin O ASO • 3-4 weeks after exposure • Culture: • swab the lesion directly • blood agar plates - hemolysis • Eliza

  38. S. pneumoniae

  39. Streptococcus pneumoniae • Gram positive cocci in pairs, singles, short chains • alpha hemolysis -- aerobic • beta hemolysis -- anaerobic • capsule -- immunogenic (84 serotypes)

  40. Diseases: • Pneumonia -- inflammation of the lungs with exudation and consolidation (solidification) • Sinusitis • Meningitis • Bacteremia

  41. Pathogenesis • virulence factor, capsule -- prevents phagocytosis • Pneumolysin is a temperate and oxygen labile hemolysin • Purpura-producing principal is released during cell autolysis • Neuraminidase -- glycoproteins and glycolipids • Autolysins, amidases -- autolyse peptidoglycan layer

  42. Mechanisms of Pathogenicity • aspiration of S. pneumoniae, an endogenous oral organism • organism colonizes the oropharynx • epiglottal reflex, coughing is inhibited

  43. Lobar Pneumoniae • multiplication in the alveolar spaces • viral infection frequently precedes bacterial infection • highly invasive due to capsule • bacteremia common • Meningitis -- most often in children • Treatment: • Penicillin, Erythromycin

  44. Laboratory Diagnosis • sputum -- gram+ cocci, lancet shaped,capsule, may appear over-decolourized • alpha-hemolytic, optochin sensitive • Quellung reaction -- specific antiserum to capsular polysaccharide • capsular antigen can be detected by very sensitive immunologic tests

  45. The End

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