Streptococcus.pptx

Streptococcus UG MBBS Class

1. Streptococcus Sayantan Banerjee AIIMS Kalyani

2. Genus Streptococcus Commensals or Parasites of man & animals or Saprophytes of decaying matter Morphology Gram-Positive Cocci in Pairs or Chains

3. Gram-Positive Streptococcus

4. Genus Streptococcus Physiology & Metabolism Facultative Anaerobes Fastidious Growth Requirements Fermentative Metabolism of Carbohydrates: Lactic acid , ethanol, acetate endproducts produced; No gas Catalase Negative (2H 2 O 2 ---> O 2 + 2H 2 O) Separation of streptococci from staphylococci Oxidase Negative ( oxidoreductase oxidizes substrate w/ O 2 ) Beta , Alpha , or Gamma Hemolysis on blood agar

5. Classification On the basis of Hemolysis divided into 3 groups: Alpha haemolytic – Viridans group, common in throat. Beta haemolytic – lysis of RBCs due to Streptolysin O (oxygen labile) & Streptolysin S (oxygen stable) Most of the pathogenic Streptococci fall into this group Gamma haemolytic – no hemolysis seen, include fecal streptococci

6. Catalase – ve , gram positive cocci arranged in chains Streptococci discovered by Billroth Non motile but twitching motility associated with polar fimbriae seen with S.sanguis isolates

7. Media Addition of crystal violet to Blood agar inhibits the growth of staphylococci, while permitting the growth of streptococci & hence acts as selective media for streptococcus (CVBA) PNF medium is also selective for Streptococci ( Polymyxin Neomycin Fusidic acid) Pikes media Todd Hewitt’s Broth

8. Lancefields group On the basis of group specific carbohydrate antigen in cell wall Beta haemolytic streptococci are further divided in to 20 serological types A to V except I & J; Antigen extracted by – HCl (lancefields method), formol, enzyme or autoclaving. Griffith Typing: Strep. Group A is subdivided based on proteins M, T, R

9. Genus Streptococcus Rebecca Lancefield Developed useful serogrouping system Classification of beta-hemolytic streptococci by group-specific cell wall carbohydrate (CHO) antigen As of 1992, Serogroups A to H and K to V Groups A, B , C, D, and G are most commonly associated with human disease Viridans streptococci and Streptococcus pneumoniae have no group-specific antigen

10. Antigenic Structure Streptococcus pyogenes (Group A) Lancefield Group-specific antigen (C polysaccharide) Complex polysaccharide in cell wall Proteins : Two major classes, M & T antigens Two minor classes, R & F M-Protein : Type-specific antigen Fimbriae-like, hairy extensions Resistant to heat and acid Trypsin Sensitive Specific adherence by Lipoteichoic acid and M-protein ( LTA-M ) complexes

11. PYOGENIC GROUP Includes 13 species Name Lancefield serogroup Hemolysis Main habitat S.pyogenes A β Humans S.agalactiae B β CAMP + Humans, cattle S.canis G β CAMP+ Animals, humans S.dysgalactiae subspecies dysgalactiae C α , β Pigs, cattle Subspecies equismilis C,G,L,A β Humans S.equi subspecies equi C β Horse, donkeys Subspecies zooepidemicus C β Cattle

12. Medically Important Streptococci

13. Antigenic Structure (cont.) Streptococcus pyogenes (Group A) Capsular Polysaccharide: Hyaluronic acid Not present in all strains Same as host hyaluronic acid (cartilage,skin etc) Nonimmunogenic Antiphagocytic Hyaluronidase (cell wall division) during late growth Lipoteichoic Acid

14. Streptococcus pyogenes (Phase Contrast)

15. Catalase – ve , gram positive cocci arranged in chains Streptococci discovered by Billroth Non motile but twitching motility associated with polar fimbriae seen with S.sanguis isolates

16. Virulence factor Activity Lipoteichoic acid adherence to epithelial cells M protein adherence to epithelial cells, inhibits phagocytosis Hyaluronic acid capsule Inhibits phagocytosis Erythrogenic toxin (Streptococcal pyrogenic exotoxin) These are three distinct toxins A, B, C (SPE A, B and C). These are superantigens . Streptolysin O Also produced by some group C and G streptococci. It is a heat labile protein. It acts by binding to cholesterol in the cell membrane and producing hole in it. It is inactivated by oxygen . Strongly antigenic and demonstration of antibodies ( Antistreptolysin O; ASO) against it indicates recent group A streptococcal infection. Streptolysin S This hemolysin is not inactivated by oxygen is responsible for hemolysis on the surface of an aerobic blood agar plate. It is not antigenic . It also has Leukocidal action.

17. Virulence factor Activity Streptokinase Produced by group A, C and G streptococci and is antigenic. Fibrinolytic action and is thought to be responsible for rapid spread of infection by preventing the formation of fibrin barrier. This property is also used therapeutically in treatment of coronary thrombosis. Deoxyribonuclease They hydrolyze nucleic acids and nucleoproteins. They are antigenic and DNAase B is the most common form produced by S.pyogenes . Anti- DNAase B is useful for the retrospective diagnosis of skin infections , where anti- streptolysin O titre may be low. Hyaluronidase Produced by strains of group A, B, C and G streptococci. It is antigenic; it is thought to play an important role in spread of infection through the tissues.

18. Functional properties of M family proteins Antiphagocytic in action but not all M serotypes So individuals may suffer from recurrent S. pyogenes infection with strains expressing different serotypes of M protein Facilitate adhesion to epithelial cells Proteins related to M proteins also present in S. equi and S. dysgalactiae

19. CLINICAL INFECTIONS Pharyngitis : Most common age group is 5 to 15 years Characterized by fever , sore throat , headache and malaise Posterior pharyngeal wall was inflamed and swollen Complications : Suppurative Peritonsillar abscess Retropharyngeal abscess Otitis media and sinusitis Non suppurative Rheumatic fever, glomerulonephritis, PANDAS

20. Superficial cutaneous infections Impetigo Occurs usually in 5 to 15 years of age group Formation of vesicular lesions that evolve into pustules which break down to form honey colored crusts Erysipelas Involvement of soft tissue and cutaneous lymphatics Present as area of edema and erythema spreading rapidly Cellulitis Present as spreading inflammatory process and involve large areas of skin and subcutaneous tissues

21. Necrotizing fascitis Involvement of superficial and deep fascia investing the muscle of extremity or trunk Presents as severe pain at site of involvement, malaise , fever and chills Streptococcal toxic shock syndrome Characterized by fever, hypotension , renal impairment and respiratory faliure Leads to multi organ failure and desquamation of skin Caused by Pyrogenic exotoxin: a superantigen

22. Pathogenicity 1. Suppurative Sore Throat – Acute Pharyngitis Necrotizing Fascitis - Fast spreading, tissue eating infection Scarlet fever – Any type of group A can produce scarlet fever that produces erythrogenic toxin, Dick test (+) Impetigo – This is caused predominantly by Strepto pyogenes ; Also be caused by gp C& G & by S. aureus Group A Streptococcus causing impetigo are frequently nephritogenic leading to glomerulonephritis Erysipelas - The sufferers are usually adults; Dick test is negative early in disease

23. Impetigo

24. Erysipelas

25. Necrotizing Fascitis

26. Pharyngitis - Gp A Streptococci are the most common bacterial cause of pharyngitis and primarily affects school age children 5 to 15 yrs age Although usually associated with streptococcal throat infections scarlet fever may occur due to infections at other sites Streptococcal strains which cause pyoderma do not cause Rheumatic fever Ludwig’s Angina – Peritonsillar or retropharyngeal abscess, diffuse cellulitis of the face.

27. Non Suppurative Acute Rheumatic Fever - ~ 3% patients develop, 2-3 wks after onset of acute pharyngitis, M types 1, 3, 5, 6, 12, 14, 17, 30, 32 & 41 Acute Glomerulonephritis – can occur either after skin or throat infection. Produced by group A also group C may be involved; Most cases of AGN occur about one week after group A type 12 infections. PANDAS – Paediatric Autoimmune Neuropsychiatric disease associated with Group A Streptococcus infection

28. Case Study A 10 years old girl presented to the OPD with fever for 8 days along with painful, tender joints in the knees, ankles, elbows, and wrists. She had symptoms of congestive heart failure, including chest pain, shortness of breath, fast heartbeat and fatigue. She also had jerky, uncontrollable body movements (called “chorea”). A murmur was heard on cardiac auscultation.

29. Major manifestations Carditis Polyarthritis Sydenham’s Chorea ( https ://www.youtube.com/watch?v=vqu5RtDh9sw ) Erythema marginatum Subcutaneous nodules Minor manifestations Clinical: fever, polyarthralgia Laboratory: elevated erythrocyte sedimentation rate or leukocyte count Electrocardiogram: prolonged P-R interval Supporting evidence of a preceding streptococcal infection within the last 45 days Elevated or rising anti- streptolysin O or other streptococcal antibody, or A positive throat culture, or Rapid antigen test for group A streptococcus, or Recent scarlet fever Diagnostic Category Criteria Primary episode of rheumatic fever Two major or one major and two minor manifestations plus evidence of preceding group A streptococcal infection

30. Strep. pyogenes (group A Strept ) (GAS) Structural components of Strep. pyogenes & Human tissue with which it cross reacts; Capsular hyaluronic a ci d - Sy novial fluid Cell wall protein M - M yocardium Cell wall c arbohydrate - C ardiac valves Cytoplasmic membrane - Vascular intima Peptidoglycan - Skin antigens

31. Cross reactions with host tissues M proteins share physiochemical properties and sequence homology with some mammalian fibrillar proteins M5,6,12 and 24 have 30% homology with myosin heavy chain and type 1 keratins M5,6 and 24 have 30% homology with human α tropomyosin So common epitopes can explain the induction of cross reactive antibodies in post streptococcal autoimmune diseases

32. Serological diagnosis - In ARF, AGN ASO level > 200 todd unit/ml Anti- DNAse B level > 300-350 IU/ml

33. Infection with group A streptococcus elicits an antibody response to streptolysin O The antibody titres reaches a peak 2 to 3 weeks after the acute infection, remains at a plateau for 3 to 6 months and reaching normal levels in next 3 to 6 months Importance of Antistreptolysin O

34. Serum antibodies to streptolysin O can be demonstrated after streptococcal infection with a frequency that increases with the severity of the infection Highest titres are found in patients with rheumatic fever ASO response following skin infection is poor due to inactivation of antigen by cholesterol present in skin Importance of Antistreptolysin O

35. A significant rise in antibody is defined as rise in titre of two or more dilution increments between acute and convalescent phase samples The Antistreptolysin O titres of > 200 Todd units in adults and > 333 Todd units in children should be considered to be elevated Importance of Antistreptolysin O

36. Viridans strep. E.g – S. sanguis , S. mitis , S. salivarius , S. milleri alpha hemolysis mouth commensals (S) to penicillin disease – dental caries, endocarditis S. sanguis – endocarditis post tooth extraction S. mutans – dental caries – M.C.

37. Viridans strep. Importance: Ability to produce endocarditis . Extracellular dextran produced by these bacteria plays an important role in adherence and propagation of the organisms on cardiac valves. Higher incidence of infective endocarditis: After bacteremia caused by dextran-producing streptococci Than when bacteremia is caused by non– dextran-producing streptococci.

38. Anginosus group : Found in human oral cavity , gastrointestinal and genital tract Sometimes isolated from infections Mitis group : Includes S. pneumoniae and several oral streptococci Salivarius group : Consist of both dairy streptococci and human oral cavity species Bovis group : Inhabit intestinal canal of human and animal species

39. Streptococcus mutans In addition to these well defined clusters term Mutans group of streptococci is used for 8 phenotypically similar species They colonize tooth surfaces of humans and animal species: responsible for dental caries Several species are not related to any phylogenetic cluster called as unclustered species