Pneumococcus
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This document summarizes information about streptococci and Streptococcus pneumoniae (pneumococcus). It describes their characteristics including being gram positive cocci that may appear in chains or pairs and are catalase negative. It discusses distinguishing streptococci from staphylococci and classifying streptococci based on hemolysis and groups A, B, C, D, F, and G. For pneumococcus, key points are that it is a normal respiratory tract commensal but an important cause of pneumonia and otitis media, having distinguishing morphology, optochin sensitivity, and a capsule visible with quellung reaction. Pneumococcal disease manifestations include pneumonia, bacteremia, and mening
Pneumococcus
- 1. STREPTOCOCCI
- 2. • •Streptococci – Gram positive cocci – chains or pairs – catalase negative – facultative anaerobe (staphylococci are catalase positive)
- 4. groupable streptococci A, B and D – most important C, G, F – rare
- 5. hemolysis reaction - sheep blood agar (alpha) – partial hemolysis green color (beta) – complete clearing – A and B (gamma) – no lysis
- 6. Classification according to hemolysis Groups A an B – Group D – or S. pneumoniae and viridans –
- 8. Introduction Pneumococci are normal commensals of the upper respiratory tract Important pathogen of pneumonia & otitis media Reclassified as Streptococcus pneumoniae Differ from Streptococci in morphology, bile solubility, optochin sensitivity & capsule
- 9. MORPHOLOGY Gram positive cocci Flame shaped/lanceolate apperance with one end broad and the other pointed. They are arranged in pairs (diplococci) They are capsulated, nonsporing and nonmotile. The capsule is visualised with Indian ink negative staining.
- 10. India-ink preparation Gram stain preparation
- 13. CULTURAL CHARECTERSTICS Pneumococci are fastidious. They grows only on enriched media. They are aerobic and facultative anaerobic. Grows at optimum temperature of 37º C. The growth is enhanced by the presence of 5-10% Co2.
- 14. Growth on blood agar: – Colonies are small, dome shaped. – With area of green discolouration (alpha hemolysis) around them. – On further incubation, Concentric rings are seen on the surface when viewed from above (draughtsman and carrom coin appearance)
- 15. Beta hemolytic Alpha haemolytic streptococci
- 16. Colonies on blood agar after 18 hrs incubation
- 17. Blood agar plate showing draughtsman colonies of pneumococcus on prolonged incubation
- 18. BIOCHEMICAL REACTION Catalase negative. Fermentation of inulin by Pneumococci is used for differentiating them from other streptococci as the later does not ferment it. They are bile soluble. Optochin sensitive
- 21. 21 Not optochin sensitive optochin sensitive
- 22. •Most rapid & most useful: identifies & specifies type of pneumococci in sputum, spinal fluid, exudates or culture •Pneumococcal specimen mixed with (polyvalent) antipneumococcla serum & methylene blue: •Positive result: Refractile & swollen capsule under oil immersion Quellung Reaction
- 24. ANTIGENIC STRUCTURE The most important antigen of the Pneumococci is: – Capsular polysaccharide – Somatic M protein – Cell wall cabohydrates(C-substance)
- 25. CAPSULAR POLYSACCHRIDES This is type specific. Pneumococci are classified into types based on the nature of capsular polysaccharide. More than 90 serotypes are recognized. The virulence of Pneumococci is dependent upon its capsule which prevents or inhibits phagocytosis. The antibody of capsular polysaccharide protects against infection.
- 26. M Protein M Protein is characteristics for each type of Pneumococci. It is not associated with virulence and antibody to M Protein is non protective.
- 27. C- Substance Pneumococci contain a species carbohydrate antigen which is named as C- Substance. It is also detected in blood of patients with some illness , this is known as C- Reactive protein (CRP).
- 28. TOXINS AND OTHER VIRULENCE FACTORS. Pneumococci produce an: – Hemolysin. – Leucocidin -Pneumolysin, is a toxin produced by Pneumococci. – It has cytolytic and complement activating properties. – It is immunogenic.
- 29. Pneumococcal disease Clinical manifestations Pneumonia Bacteremia Meningitis
- 30. PATHOGENESIS Pneumococcus is one of the most common bacteria causing pneumonia. – Lobar pneumonia – bronchopneumonia
- 31. Meningitis It is most serious of pneumococcal infection. It is the second most important cause of pyogenic meningitis after N.meningitidis. Common in children. Spreads from the pharynx to the meninges via blood stream.
- 32. Other infections Pneumococci may also produce: – Empyema – Pericarditis – Otitis media – Peritonitis – suppurative arthritis.
- 33. Laboratory Diagnosis Samples :according to site Collect and transport Direct microscopy Culture and identification Antibiotic sensitivity
- 34. Inhibition by optochin Growth of colonies of Streptococcus pneumoniae is inhibited by optochin contained in the disk applied to the blood agar plate Lysis by bile salts: Bile salt such as sodium deoxycholate, dissolves Streptococcus pneumoniae and clear the turbidity of the heavy inoculum of organisms Quellung reaction Capsule of Streptococcus pneumoniae swells in the presence of specific pneumococcal antiserum Morphology They are gram positive cocci arranged in pairs. Lanconate shaped Capsulated organism
- 35. 35 GRAM POSITIVE COCCI S. aureus Beta hemolytic mannitol yellow + - Staphylococcus (Clusters) Streptococcus (pairs & chains) Catalase BETA: Bacitracin S. pyogenes (group A) CAMP/ Hippurate S. agalactiae (group B) Coagulase S. epidermidis Non-hemolytic mannitol white ALPHA: Optochin /Bile Solubility S. pneumoniae GAMMA OR ALPHA: Bile Esculin 6.5% NaCl Group D Enterococcus Bile Esculin 6.5% NaCl Group D Non-Enterococcus Note: S. viridans is ALPHA hemolytic and negative for all the tests below + + + + + + + - - Summary Figure (Identification Scheme) Hemolysis/Test