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Streptococcus
Streptococcus are Gram-positive cocci that form chains. They include pathogenic and commensal species. S. pyogenes is a beta-hemolytic streptococcus of Lancefield group A that causes pyogenic infections like tonsillitis and scarlet fever. It produces toxins like streptolysins and pyrogenic exotoxins. Rheumatic fever and acute glombulonephritis are non-suppurative complications of S. pyogenes infections. S. pneumoniae is a common cause of pneumonia and meningitis. It is an alpha-hemolytic encapsulated diplococcus that is bile soluble and optochin sensitive. Identification involves culture, Gram stain, biochemical tests and serotyping
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Streptococcus
- 1. Streptococcus Dr. Kanwal DeepSingh Lyall M.D. Microbiology
- 2. General Characteristics • STREPTOS– twisted / coiled - Billroth (1874) • Rosenbach – (1884) – S. pyogenes • GPC in Chains – divide in one plane and daughter cells remain attached • 0.5 – 1 µm • catalase negative, • Normal flora and opportunistic pathogens • Exacting nutritional demands – Blood , serum , sugars (only acid , no gas)
- 3. Structure Carb. C Ag– Lancefield’s Grouping M – protein – Most important, inhib. Phagocystosis , heat & acid stable , role in Rheumatic fever T & R proteins - no virulence Others – M assoc. protien , MAP Serum opacity factor
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- 5. Streptococcus Oxygen requirement Aerobes &facultative anaerobes Hemolysis Alpha HS Beta HS NHS Obligate anaerobes e.g. Peptostreptococci GREEN Partial H’lysis Small zone Viridans Group Pneumococci Clear, Complete, 2 – 4mm Streptolysin O O2 labile, Seen in deep subsurface colonies, Antigenic in nature Streptolysin – S O2 stable, surface h’lysis, non-antigenic 20 Lancefiled groups , based on carbohydrate “C” antigen , A-V without I & J Group – A ( S. pyogenes ) , Griffith serotypes – based on “M “ Protein, 1 – 80 Enterocococcus Non- enterococcus group
- 6. Streptococcus Pyogenes • BetaHS, Lancefield group A • H’lysis ↑ by 10% CO2 • Granular turbidity and powdery deposit • Selective media – Crystal violet BA • Non- soluble in 10 % bile salts , PYR + VE • Delicate, stored in RCM @ 4° C
- 7. Toxins 1. Hemolysins O& S , ASO ( > 200 significant) 2. Pyrogenic / erythrogenic exotoxin : – Rash in scarlet fever – Types A, B, C – Super-antigens – Dick test – local injection in susceptible – local erythema – Schultz – Charlton Reaction – injection of antisera in to above rash – blanching
- 8. Enzymes 1. Streptokinase –lysis of human fibrin clot ( Fibrinogen – fibrin ) 2. DNAase – Group A, B, C & D – liquid pus 3. Nicotinamide – adenine – dinucleotidease (NADase ) – leucotoxic 4. Hyaluronidase – breaks down hyaluronic acid – favors spread
- 9. Diseases Pyogenic • RTI –tonsillitis , mastoiditis, • Scarlet fever in cold countries • Skin infections – lymphangitis, cellulitis, Impetigo, erysepellas Non – Suppurative complications • Rheumatic fever • Acute Glomerulonephritis
- 10. • Rheumatic fever: – d/t repeated throat infections, marked immune response, heredity tendency, penicillin prophylaxis • Acute Glomerulonephritis : – throat / skin infections, single infection, late pyodermal and early throat strains, moderate immune response , heredity tendency is not known
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- 12. Sample Transfer immidately orPike’s media ( BA + C. violet + Na. azide) Gram stain – CSF, PUS Culture – BA @ 37 C X 18 – 24 hrs Pin point colonies → Gram stain , GPC in chains Catalase – ve , PYR + VE , Serum sugars (Ribose), Bacitracin , CAMP Test AST, Lancefield Grouping
- 13. CAMP Test • Christie,Atkins and Munch – Peterson Beta HS S. aureus streak ( Beta hemolysin enhances hemolysis) Enhanced zone of Hemolysis (Butterfly appearance ) Positive test Negative test
- 14. Lancefield Grouping -Carbohydrate C Ag extracted – Precipitation test Growth in Todd – Hewitt broth HCL- Lancefield’s Streptomyces albus enzyme – Maxtard’s Formaldehyde – Fuller’s Autoclave – Rantz & Randall’s
- 15. • Group Astreptococcus • St. pyogenes • Hippurate hydrolysis – ve • CAMP – ve • Bacitracin Sensitive • Does not ferment Ribose • Group B streptococcus • St. agalactiae • Hippurate hydrolysis – ve • CAMP + ve • Neonatal septicaemia • Meningitis • Bacitracin resistant • Ribose fer. + ve
- 16. NHS (Gamma H’lytic) •Non – enterococcal group • S. Bovis • S. equinus • S. suis • S. mutans • Enterococcal Group • E. faecalis (m/c) • E. faecium • E. durans • E. avium • Normal flora – GUT • Heat R ( 60 °C x 30 m) • Grow in 40 % bile, @ 45 ° C, 6.5% NaCl, @pH 9.6 , PYR + ve
- 17. Viridans Group • S.salivarius • S. sanguis • S. Milleri (anginosus) • Cause – SABE, Dental Caries
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- 19. Pneumococcus • S. pneumoniae •Gram positive encapsulated (polysach) flame/lancelate shaped diplococci • Bile soluble , optochin sensitive • Aerobes/ F. anaerobes • Normal upper resp. tract flora • Common cause of pneumonia & OM in children
- 20. • Draughtsman colonieson prolonged incub. • Normaly alpha HS – Beta HS under anaerobic conditions – d/t – pneumolysin O • Autolysis - ↑ by bile salts ( 10% in tubes, 2% on plate) – d/t amidase – breaks bond between alainin & muramic acid in peptidoglycan • Hiss serum sugars – acid only • Insulin fermentation + ve and sensitive to Optochin (5 µg) • Capsular polysachride ( 90 types) – aka Soluble specific substance – Vaccine m/c 23 types
- 21. • M –protein : Non – virulent, strain specific • C substance – species specific – precipiated buy abnormal protein – present in acute infections, injury – acute phase reactant – CRP – produced by hepatocytes • Quellung (Neufeld reaction) : Pneumococci + nantisera _ Meth. Blue = capsular swelling ( d/t ↑ in refractive index)
- 22. Toxins and virulencefactors • Hemolysin – oxygen labile • Leucocidin • Capsule – most important • Pneumolysin – cytotoxic, activates compliment, immunopgenic
- 23. Pathogenicity • M/C causeof bacterial pneumonia • Lobar pneumonia – adults ( 1-12), children ( 6,14,19,23) • Bronchopneumonia – almost always 2° infection – all serotypes • 2nd commonest cause of meningitis • Phyranx blood stream meninges • Empyema, pericarditis, conjunctivits etc.
- 24. Lab diagnosis • Sample– CSF , Sputum , exudates • Immediately transfer or keep at 37° C (H. influenzae dies at 37 low t°) • Direct microscopy or antigen fdetection by LAT or coaglutination) • BA @ 37 C x 18 – 24 hrs • Colonies – alpha hs, G/S , Biochem. Rx (catalase, inulin fermentation, bile sol, optochin) • Animal pathogenicity – mies dies on IP injection x 48 hrs – s/c heart nlodd, peritoneal extraxt – pneumo.
- 25. India Ink GramSatin • Quellung reaction
- 26. • Pneumococcus • Capsulated •Flame shaped • Draugtsman colonies • Bile sol • Granular tubidity • Insulin ferm + • Optochin sensitive • Fatal to mice • Viridans gp. • Non- cap. • Pairs , oval • Dome shapped • Non-bole sol. • Deposit ( heavy chains) • Rest negative