streptococci

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

1. STREPTOCOCCUSSTREPTOCOCCUS

2. Strepto-cocci

3. •Commensals or Parasites of man &
animals
•or
•Saprophytes of decaying matter

4. Genus Streptococcus
Morphology
Gram-Positive Cocci in Pairs or Chains
v/s
Staph – gram positive cocci in clusters (grape like)

5. Gram-Positive
Streptococcus

6. •Gram positive cocci in clusters

7. Classification
•On the basis of their growth characteristics
on blood agar
•Alpha hemolytic
•Beta hemolytic
•Gamma hemolytic

8. Example –
Streptococcus viridans (Viridans = green)
Streptococcus pneumoniae

10. Example – enterococcus group

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

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

16. Streptococcus Pyogenes
(Group A beta hemolytic)

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

18. Morphology
•Cocci in long chains

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

20. Growth characteristics
•Facultative anaerobe, grows best in
presence of 10% CO
2
•Grows on enriched media only
•Beta hemolysis around colonies on blood
agar

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

23. Biochemical reactions
•Ferment sugars – produce acid , no gas
•Catalase negative
•Catalase helps to differentiate staphylococci
from streptococci

24. Catalase test
•Add hydrogen peroxide to culture material

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

26. Resistance
•Most are still susceptible to penicillin and
erythromycin

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

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

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

30. Epidemiology
•Source – human upper respiratory tract –
throat, pharynx, nose
•Transmission – direct contact, fomites

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

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)

33. Respiratory infections
•Tonsillitis
•Pharyngitis

34. •tonsillitis

35. •pharyngitis

36. Skin and soft tissue infections
•Skin
–Erysipelas – involves lymphatics – older pts
–Impetigo – young children
–Pyoderma
•Soft tissue
–Cellulitis
–Necrotising fascitis

37. Erysipelas

38. Impetigo

39. Pyoderma

40. Cellulitis

41. Necrotising fascitis
flesh eating bacteria (anaerobes)

42. Non suppurative complications
After 1-3 weeks of primary infection
Due to cross reactivity
II

43. Acute rheumatic fever
•Follows streptococcal sore throat

44. Acute glomerulonephritis
•Cross reaction between streptococci and
kidney tissues

45. Rheumatic heart disease

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

47. Suppurative infections
•Examination of pus/throat swabs
•Microscopy, staining and culture
•Gram stain
•Blood agar

48. Non suppurative infections
•Demonstration of antibodies
•Like ASO and anti DNA ase B

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

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

51. OTHER STREPTOCOCCI
BETA HEMOLYTIC - GROUP B
AND GROUP D
ALPHA HEMOLYTIC (VIRIDANS
GROUP)– STREPTOCOCCUS
PNEUMONIAE

52. Group B Streptococcus
Streptococcus agalactiae

53. Group B Streptococcus
S. agalactiae
1.Infect newborns
2.Infection acquired through maternal vagina during
birth
3.Presents as meningitis, pneumonia or septicemia

54. Diagnostic Laboratory Tests
• CAMP factor positive
• Hippurase positive

55. CAMP (Christie, atkins, munch-
peterson) Factor Test
S. aureus
(Spingomyelinase C)
Group B
Streptococcus
(CAMP Factor)
Group A
Streptococcus
Enhanced
Zone of
Hemolysis

56. Hippurase NEG
Streptococcus agalactiae not added

57. Hippurase POS
Grp B Streptococci

58. Viridans group
Streptococcus pneumoniae
• Commonly referred to as pneumococcus

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

60. •Lancet shaped (one end broad, other
pointed)
•Capsulated
•Diplococci

61. S. pneumoniae: lancet-shaped diplococcus

62. S. pneumoniae
• Diplococcus

63. Capsular stain

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

65. Growth characteristics
•Alpha hemolysis on blood agar
•On further incubation, the colonies become
flat with raised edges and central elevation
resembling carrom coins

66. Example –
Streptococcus viridans (Viridans = green)
Streptococcus pneumoniae

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

68. Biochemical reactions
•Hiss serum water – fermentation of inulin
•Bile solubility

69. Inulin fermentation

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

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

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

75. Pathogenicity and virulence
•Capsule
•Toxins – pneumolysin
•C reactive protein

76. Capsule

77. Pneumolysin
•Membrane damaging toxin
•Cytotoxic activity

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

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

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

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

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

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

84. Laboratory diagnosis
•Sample
–sputum – pneumonia
–septicemia - blood culture
–Otitis media - fluid from middle ear
–Meningitis - CSF
•Method
–Gram stain, microscopy
–culture

85. •Latex agglutination for pneumococcal
antigen in serum of patients

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

87. Treatment
•Penicillin
•Amoxycillin
•ceftriaxone/ceftazidime
•Vancomycin

88. Prophylaxis
•Pneumococcal conjugate vaccine is
available
•Given to splenectomy patients, sickle cell
anemia patients and susceptible individuals

89. GROUP D STREPTOCOCCI
Enterococcus faecalis
Enterococcus faecium
• GI tract of humans and animals
• Group D carbohydrate cell wall antigen
• Formerly Streptococcus

90. •Cause UTI, wound infection
•Endocarditis
•Intra abdominal abcesses