Gram Reaction
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1 Streptococcus Hugh B. Fackrell Filename:Strept.ppt 3/12/2016 2 Streptococcus Outline Streptococcus Characteristics Streptococcal Diseases 3/12/2016 3 Streptococcus: characteristics Genus definition Growth requirements Capsule Colonial morphology Hemolysis Destruction of RBCs Hemolysins molecules that destroy RBCs 3/12/2016 4 Streptococcus Genus 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 3/12/2016 5 Fastidious Most Streptococci are fastidious in their growth requirements Grow poorly on nutrient agar Grow well on blood agar 3/12/2016 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 produce hyaluronidase 3/12/2016 7 Colonial Morphology GLOSSY: no capsule, colonies small MUCOID: capsule, colonies are large, glistening, viscous MATT:capsule, older colonies are dried, flatter rougher Glossy Mucoid 3/12/2016 8 Two Forms of Hemolysis Alpha Hemolysis Greening “viridans” Beta Hemolysis Clearing (Gamma hemolysis = no lysis) 3/12/2016 9 Streptococcal Beta Hemolysis Two hemolysins Both cause clearing Both involved in disease 3/12/2016 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 3/12/2016 11 Hemolysin O Oxidized in air oxygen labile (reversible) Protein Cardiotoxic patients develop antibodies Subsurface colony of Streptococcus ASOT producing Hemolysin 0 cholesterol labile (irreversible) Antistreptolysin O test 3/12/2016 12 Streptococcus pyogenes Suppurative Diseases Pharyngitis Scarlet Fever Erysipalas ( St. Antony’s fire) Cellulitis Puerperal Fever Sepsis Meningitis Pneumonia Subacute Bacterial Endocardititis Otitis Media 3/12/2016 13 Diseases of S. pyogenes 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: 3/12/2016 14 Streptococcal Suppuration 3/12/2016 15 Puerperal Fever “Childbirth Fever” Membranes of genital tract ruptured Semmelweis fulminating septicemia fatal 24-48 hr S. pyogenes 60-75% of cases S. pyogenes Not isolated from vagina of healthy females before birth 50-60% from physician rest from own nose & throat Anaerobic streptococci 20-25% 3/12/2016 16 Post vaccination Streptococcal Infection 3/12/2016 17 Streptococcal Cellulitis 3/12/2016 18 Scarlet Fever 3/12/2016 19 Scarlet Fever Rash Peticial hemorrhage Pin point Subcutaneous Erythrogenic toxin Scarletina toxin causes rash associated with a temperate phage 3/12/2016 20 Scarlet Fever Strawberry Tongue 3/12/2016 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 3/12/2016 22 Erysipalas Secondary invasion minor Skin reddened thickened later original lesion purple Bacteria only in advancing edge 3/12/2016 23 Erysipalas: butterfly rash Butterfly rash common near nose spreads after 4-6 days Septicemia common complication No toxin No immunity repeated possible attacks 3/12/2016 24 Rheumatic Fever autoimmune acute glomerulonephritis Acute, non suppurative post streptococcal inflammation Joints, heart valves,myocardium,nerves chorea- inflammation of nerves 3/12/2016 25 Scarred heart valves reduced cardiac output heart failure Mitral valve stenosis edema, hypertension, hematuria and proteinuria 3/12/2016 26 Rheumatic Endocarditis Scarred heart valves 3/12/2016 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 3/12/2016 28 Aschoff Bodies Inflammation of myocardium Mononuclear cell infiltration Granuloma-like nodules Characteristc of rheumatic fever 3/12/2016 29 Streptococcal Antigens Lancefield groups M antigens T antigens R antigens 3/12/2016 30 Streptococcus Lancefield Groups Rebecca Lancefield Grouped by presence of distinctive cell wall antigens Polysacchardies Antigens labelled A-T exclude or glycero teichoic acids I&J Group A Streptococci Clinically Important 3/12/2016 31 Lancfield Groups S. pneumoniae N/A S.pyogenes -- Lancefield Group A S.agalactiae -- Lancefield Group B Enterococcus-Lancefield Group D Viridans group 3/12/2016 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 3/12/2016 33 Group D Streptococci 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 3/12/2016 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 3/12/2016 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 3/12/2016 36 Enzymes Streptokinase A & B: lyse blood clots DNA ase: depolymerase Hyaluronidase: hyaluronic DNA in pus acid DPN ase 3/12/2016 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 3/12/2016 38 S. pneumoniae 3/12/2016 39 Streptococcus pneumoniae Gram positive cocci in pairs, singles, short chains alpha hemolysis -- aerobic beta hemolysis -- anaerobic capsule -- immunogenic (84 serotypes) 3/12/2016 40 Diseases: Pneumonia -- inflammation of the lungs with exudation and consolidation (solidification) Sinusitis Meningitis Bacteremia 3/12/2016 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 3/12/2016 42 Mechanisms of Pathogenicity aspiration of S. pneumoniae, an endogenous oral organism organism colonizes the oropharynx epiglottal reflex, coughing is inhibited 3/12/2016 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 3/12/2016 44 Laboratory Diagnosis sputum -- gram+ cocci, lancet shaped,capsule, may appear overdecolourized alpha-hemolytic, optochin sensitive Quellung reaction -- specific antiserum to capsular polysaccharide capsular antigen can be detected by very sensitive immunologic tests 3/12/2016 45 The End 3/12/2016
