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

1. STREPTOCOCCUS
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2. Strepto-cocci
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3.  Commensals or Parasites of man & animals
 or
 Saprophytes of decaying matter
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4. Genus Streptococcus
Gram-Positive Cocci in Pairs or Chains
v/s
Staph – gram positive cocci in clusters (grape like)
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5. Gram-Positive
Streptococcus
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6.  Gram positive cocci in clusters
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7. Classification
 On the basis of their growth characteristics on
blood agar
 Alpha hemolytic
 Beta hemolytic
 Gamma hemolytic
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8. Example –
Streptococcus viridans (Viridans = green)
Streptococcus pneumoniae
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9. 9

10. Example – enterococcus group
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11. 11

12. 12

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
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14. Group A beta hemolytic streptococci /
strep pyogenes
 These are further subdivided according to sell
surface M, T and R antigens
 Griffith typing
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15. 15

16. Streptococcus Pyogenes
(Group A beta hemolytic)
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17. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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18. Morphology
 Cocci in long chains
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19. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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20. Growth characteristics
 Facultative anaerobe, grows best in presence
of 10% CO2
 Grows on enriched media only
 Beta hemolysis around colonies on blood
agar
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21. 21

22. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
22

23. Biochemical reactions
 Ferment sugars – produce acid , no gas
 Catalase negative
 Catalase helps to differentiate staphylococci
from streptococci
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24. Catalase test
 Add hydrogen peroxide to culture material
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25. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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26. Resistance
 Most are still susceptible to penicillin and
erythromycin
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27. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
27

28. Pathogenicity and virulence
 Antigenic structure
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Antigens on surface of strep cross react with body proteins
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Capsular hyaluronic acid – human joints – autoimmune arthritis
Carbohydrate antigen – cardiac valves – rheumatic heart
disease
 Toxins
 Enzymes
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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
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29. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
29

30. Epidemiology
 Source – human upper respiratory tract –
throat, pharynx, nose
 Transmission – direct contact, fomites
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31. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
31

32. Diseases caused
 Pus producing (suppurative)
Respiratory infections
 Skin and soft tissue infections
 Genital infections
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 Non suppurative
Acute rheumatic fever
 Rheumatic heart disease
 Acute glomerulonephritis (kidney)
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33. Respiratory infections
 Tonsillitis
 Pharyngitis
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34.  tonsillitis
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35.  pharyngitis
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36. Skin and soft tissue infections
 Skin
Erysipelas – involves lymphatics – older pts
 Impetigo – young children
 Pyoderma
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 Soft tissue
Cellulitis
 Necrotising fascitis
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37. Erysipelas
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38. Impetigo
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39. Pyoderma
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40. Cellulitis
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41. Necrotising fascitis
flesh eating bacteria (anaerobes)
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42. Non suppurative complications
After 1-3 weeks of primary infection
Due to cross reactivity
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43. Acute rheumatic fever
 Follows streptococcal sore throat
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44. Acute glomerulonephritis
 Cross reaction between streptococci and
kidney tissues
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45. Rheumatic heart disease
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46. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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47. Suppurative infections
 Examination of pus/throat swabs
 Microscopy, staining and culture
 Gram stain
 Blood agar
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48. Non suppurative infections
 Demonstration of antibodies
 Like ASO and anti DNA ase B
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49. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
49

50. Treatment
 Penicillin
 Erythromycin
 Drugs have no effect if non suppurative
complications have developed
 Prophylaxis – can prevent rheumatic fever,
not glomerulonephritis
50

51. OTHER STREPTOCOCCI
BETA HEMOLYTIC - GROUP B
AND GROUP D
ALPHA HEMOLYTIC (VIRIDANS
GROUP)– STREPTOCOCCUS
PNEUMONIAE
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52. Group B Streptococcus
Streptococcus agalactiae
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53. Group B Streptococcus
S. agalactiae
1. Infect newborns
2. Infection acquired through maternal vagina during
birth
3. Presents as meningitis, pneumonia or septicemia
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54. Diagnostic Laboratory Tests
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CAMP factor positive
Hippurase positive
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55. CAMP (Christie, atkins, munchpeterson) Factor Test aureus
S.
Group B
Streptococcus
(Spingomyelinase C)
(CAMP Factor)
Group A
Streptococcus
Enhanced
Zone of
Hemolysis
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56. Hippurase NEG
Streptococcus agalactiae not added
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57. Grp B Streptococci
Hippurase POS
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58. Viridans group
Streptococcus pneumoniae
• Commonly referred to as pneumococcus
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59. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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60.  Lancet shaped (one end broad, other
pointed)
 Capsulated
 Diplococci
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61. S. pneumoniae: lancet-shaped diplococcus
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62. S. pneumoniae
• Diplococcus
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63. Capsular stain
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64. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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65. Growth characteristics
 Alpha hemolysis on blood agar
 On further incubation, the colonies become
flat with raised edges and central elevation
resembling carrom coins
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66. Example –
Streptococcus viridans (Viridans = green)
Streptococcus pneumoniae
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67. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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68. Biochemical reactions
 Hiss serum water – fermentation of inulin
 Bile solubility
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69. Inulin fermentation
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70. 70

71. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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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
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73. 73

74. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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75. Pathogenicity and virulence
 Capsule
 Toxins – pneumolysin
 C reactive protein
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76. Capsule
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77. Pneumolysin
 Membrane damaging toxin
 Cytotoxic activity
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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
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79. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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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
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81. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
81

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
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83. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
83

84. Laboratory diagnosis
 Sample
sputum – pneumonia
 septicemia - blood culture
 Otitis media - fluid from middle ear
 Meningitis - CSF
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 Method
Gram stain, microscopy
 culture
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85.  Latex agglutination for pneumococcal antigen
in serum of patients
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86. Description headings
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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87. Treatment
 Penicillin
 Amoxycillin
 ceftriaxone/ceftazidime
 Vancomycin
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88. Prophylaxis
 Pneumococcal conjugate vaccine is available
 Given to splenectomy patients, sickle cell
anemia patients and susceptible individuals
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89. GROUP D STREPTOCOCCI
Enterococcus faecalis
Enterococcus faecium
• GI tract of humans and animals
• Group D carbohydrate cell wall antigen
• Formerly Streptococcus
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90.  Cause UTI, wound infection
 Endocarditis
 Intra abdominal abcesses
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91. 91