streptococci

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this is a series of lectures on microbiology, useful for undergraduate and post graduate medical and paramedical students..lecture on streptococci

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streptococci

  1. 1. STREPTOCOCCUS 1
  2. 2. Strepto-cocci 2
  3. 3.  Commensals or Parasites of man & animals  or  Saprophytes of decaying matter 3
  4. 4. Genus Streptococcus Gram-Positive Cocci in Pairs or Chains v/s Staph – gram positive cocci in clusters (grape like) 4
  5. 5. Gram-Positive Streptococcus 5
  6. 6.  Gram positive cocci in clusters 6
  7. 7. Classification  On the basis of their growth characteristics on blood agar  Alpha hemolytic  Beta hemolytic  Gamma hemolytic 7
  8. 8. Example – Streptococcus viridans (Viridans = green) Streptococcus pneumoniae 8
  9. 9. 9
  10. 10. Example – enterococcus group 10
  11. 11. 11
  12. 12. 12
  13. 13. Beta hemolytic streptococci Lancefield grouping  Group A to Group V without I and J  Divided according to differences in Cell wall carbohydrate antigen  Out of all these, those of Group A known as streptococcus pyogenes produce majority of human infections  Group B are known as S agalactiae 13
  14. 14. Group A beta hemolytic streptococci / strep pyogenes  These are further subdivided according to sell surface M, T and R antigens  Griffith typing 14
  15. 15. 15
  16. 16. Streptococcus Pyogenes (Group A beta hemolytic) 16
  17. 17. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 17
  18. 18. Morphology  Cocci in long chains 18
  19. 19. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 19
  20. 20. Growth characteristics  Facultative anaerobe, grows best in presence of 10% CO2  Grows on enriched media only  Beta hemolysis around colonies on blood agar 20
  21. 21. 21
  22. 22. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 22
  23. 23. Biochemical reactions  Ferment sugars – produce acid , no gas  Catalase negative  Catalase helps to differentiate staphylococci from streptococci 23
  24. 24. Catalase test  Add hydrogen peroxide to culture material 24
  25. 25. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 25
  26. 26. Resistance  Most are still susceptible to penicillin and erythromycin 26
  27. 27. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 27
  28. 28. Pathogenicity and virulence  Antigenic structure  Antigens on surface of strep cross react with body proteins   Capsular hyaluronic acid – human joints – autoimmune arthritis Carbohydrate antigen – cardiac valves – rheumatic heart disease  Toxins  Enzymes      Streptolysin O – ASO titre for diagnosis Streptolysin S – for hemolysis around colonies Streptokinase – lysis of clots – given iv for treatment of MI DNA ase – Anti DNAase is useful for diagnosis of S. pyogenes skin infection Hyaluronidase – breaks down tissues – helps in spread of strep infection 28
  29. 29. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 29
  30. 30. Epidemiology  Source – human upper respiratory tract – throat, pharynx, nose  Transmission – direct contact, fomites 30
  31. 31. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 31
  32. 32. Diseases caused  Pus producing (suppurative) Respiratory infections  Skin and soft tissue infections  Genital infections   Non suppurative Acute rheumatic fever  Rheumatic heart disease  Acute glomerulonephritis (kidney)  32
  33. 33. Respiratory infections  Tonsillitis  Pharyngitis 33
  34. 34.  tonsillitis 34
  35. 35.  pharyngitis 35
  36. 36. Skin and soft tissue infections  Skin Erysipelas – involves lymphatics – older pts  Impetigo – young children  Pyoderma   Soft tissue Cellulitis  Necrotising fascitis  36
  37. 37. Erysipelas 37
  38. 38. Impetigo 38
  39. 39. Pyoderma 39
  40. 40. Cellulitis 40
  41. 41. Necrotising fascitis flesh eating bacteria (anaerobes) 41
  42. 42. Non suppurative complications After 1-3 weeks of primary infection Due to cross reactivity 42
  43. 43. Acute rheumatic fever  Follows streptococcal sore throat 43
  44. 44. Acute glomerulonephritis  Cross reaction between streptococci and kidney tissues 44
  45. 45. Rheumatic heart disease 45
  46. 46. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 46
  47. 47. Suppurative infections  Examination of pus/throat swabs  Microscopy, staining and culture  Gram stain  Blood agar 47
  48. 48. Non suppurative infections  Demonstration of antibodies  Like ASO and anti DNA ase B 48
  49. 49. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 49
  50. 50. Treatment  Penicillin  Erythromycin  Drugs have no effect if non suppurative complications have developed  Prophylaxis – can prevent rheumatic fever, not glomerulonephritis 50
  51. 51. OTHER STREPTOCOCCI BETA HEMOLYTIC - GROUP B AND GROUP D ALPHA HEMOLYTIC (VIRIDANS GROUP)– STREPTOCOCCUS PNEUMONIAE 51
  52. 52. Group B Streptococcus Streptococcus agalactiae 52
  53. 53. Group B Streptococcus S. agalactiae 1. Infect newborns 2. Infection acquired through maternal vagina during birth 3. Presents as meningitis, pneumonia or septicemia 53
  54. 54. Diagnostic Laboratory Tests   CAMP factor positive Hippurase positive 54
  55. 55. CAMP (Christie, atkins, munchpeterson) Factor Test aureus S. Group B Streptococcus (Spingomyelinase C) (CAMP Factor) Group A Streptococcus Enhanced Zone of Hemolysis 55
  56. 56. Hippurase NEG Streptococcus agalactiae not added 56
  57. 57. Grp B Streptococci Hippurase POS 57
  58. 58. Viridans group Streptococcus pneumoniae • Commonly referred to as pneumococcus 58
  59. 59. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 59
  60. 60.  Lancet shaped (one end broad, other pointed)  Capsulated  Diplococci 60
  61. 61. S. pneumoniae: lancet-shaped diplococcus 61
  62. 62. S. pneumoniae • Diplococcus 62
  63. 63. Capsular stain 63
  64. 64. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 64
  65. 65. Growth characteristics  Alpha hemolysis on blood agar  On further incubation, the colonies become flat with raised edges and central elevation resembling carrom coins 65
  66. 66. Example – Streptococcus viridans (Viridans = green) Streptococcus pneumoniae 66
  67. 67. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 67
  68. 68. Biochemical reactions  Hiss serum water – fermentation of inulin  Bile solubility 68
  69. 69. Inulin fermentation 69
  70. 70. 70
  71. 71. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 71
  72. 72. Resistance  Pneumococcus is sensitive to optochin – used for typing  Resistance to penicillin – third generation cephalosporin like ceftriaxone  May be resistant to third gen ceph also 72
  73. 73. 73
  74. 74. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 74
  75. 75. Pathogenicity and virulence  Capsule  Toxins – pneumolysin  C reactive protein 75
  76. 76. Capsule 76
  77. 77. Pneumolysin  Membrane damaging toxin  Cytotoxic activity 77
  78. 78. C reactive protein  Abnormal immunoglobulin against C protein of S. pneumoniae appears in serum of patients  Also seen in acute phase of infections and inflammations  CRP titre is tested in acute infections 78
  79. 79. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 79
  80. 80. Epidemiology  Source – respiratory tract of humans  Spread – droplets  Carriers – pharynx  Low immunity is responsible for fulminant infections RSV infection, pulmonary congestion, stress, malnutrition, alcoholism  Splenectomy  Sickle cell disease  80
  81. 81. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 81
  82. 82. Diseases caused  Middle ear – otitis media  Para nasal sinuses – sinusitis  Respiratory tract – pneumonia, bronchitis, empyema  Meningitis is secondary to otitis media, penumonia, sinusitis and conjunctivitis 82
  83. 83. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 83
  84. 84. Laboratory diagnosis  Sample sputum – pneumonia  septicemia - blood culture  Otitis media - fluid from middle ear  Meningitis - CSF   Method Gram stain, microscopy  culture  84
  85. 85.  Latex agglutination for pneumococcal antigen in serum of patients 85
  86. 86. Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 86
  87. 87. Treatment  Penicillin  Amoxycillin  ceftriaxone/ceftazidime  Vancomycin 87
  88. 88. Prophylaxis  Pneumococcal conjugate vaccine is available  Given to splenectomy patients, sickle cell anemia patients and susceptible individuals 88
  89. 89. GROUP D STREPTOCOCCI Enterococcus faecalis Enterococcus faecium • GI tract of humans and animals • Group D carbohydrate cell wall antigen • Formerly Streptococcus 89
  90. 90.  Cause UTI, wound infection  Endocarditis  Intra abdominal abcesses 90
  91. 91. 91

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