streptococci ppt please do like and share

1. STREPTOCOCCAL
INFECTIONS
1

2. 2
INTRODUCTION:
•STREPTOCOCCI are widely distributed in nature and
some are members of the normal flora while others are
pathogenic
•Pathogenicity can be attributed in part to
• Infection by the organism, and
• Sensitization to them
•They elaborate a variety of extracellular substances and
enzymes
•They are a large and heterogeneous group of bacteria
impossible to classify into one system
•Classification by various properties is key to understanding
their medical importance.

3. 3
IDENTIFICATION:
•Gram positive spheres (cocci) like staphylococci
•But unlike staphylococci that appear in clusters, streptococci
appear in strips (chains) on gram stain – determined by their
planes of division
•1µm in diameter and usually capsulated
•Facultative anaerobes (some species – microaerophilic)
• Some – Capnophilic
•For most – growth and hemolysis are aided by incubation in 10% CO2
•They are catalase negative
•Non-sporing bacteria and non-motile.
•Growth requires enriched media containing blood or serum.

4. IDENTIFICATION:
• Catalase test:
•Catalase converts H2O2(which is used by macrophages and neutrophils) to
Water and O2
4
Catalase +ve
Staphylococci
Catalase –ve
Streptococci

5. 5
CLASSIFICATION:
• Based on the hemolytic properties:
▪ Beta-hemolytic: - clear zone of hemolysis around the colony
▪ Alpha-hemolytic: - greenish discolouration of the culture medium around the
colony (partial hemolysis)
▪ Gamma-hemolytic: - no hemolysis of RBCs (Non-hemolytic streptococci)
• Based on antigenic characteristics of cell wall CHO (C – carbohydrate)
–Lancefield Antigens (Serologic Classification from A to V):
▪ Out of over 30 species of streptococci, only 5 are significant human
pathogens
▪ 3 have Lancefield Antigens:
▪ Group A – (S. pyogenes),
▪ Group B – (S. agalactiae), and
▪ Group D – (Enteroccoci + Non-enterococci)
▪ 2 have no Lancefield antigens – Lancefield Non-groupable:
▪ S. pnuemoiae, and
▪ Viridans group Streptoccoci

6. CLASSIFICATION:
• Hemolysis on Blood agar:
6

7. 7
CLASSIFICATION:
•Historically, Lancefield antigens have been used as a major
way of differentiating the many streptococci though not
applicable to a number of organisms including some
pathogenic species
•Identification of Streptococcal organisms require a
combination of several characteristics including:
• Antigenic composition including Lancefield antigens,
• Patterns of hemolysis,
• Biochemical reactions,
• Growth characteristics, and
• Genetic studies

8. CLASSIFICATION:
8

9. CLASSIFICATION:
9

10. 10
BIOCHEMICAL REACTIONS:
Differentiation between beta-hemolytic
streptococci:
•Bacitracin susceptibility test
•CAMP test
•Bile Esculin Test

11. 11
BIOCHEMICAL REACTIONS:
Bacitracin Test -
• Bacitracin susceptibility Test:
• Specific for S. pyogenes (Group A) – for its presumptive identification
• Principle:
• To distinguish between S. pyogenes (susceptible to B) & non group A such
as S. agalactiae (resistant to B)
• Bacitracin will inhibit the growth of Group A – S. pyogenes giving zone of
inhibition around the disk
• Procedure:
• Inoculate BAP with heavy suspension of tested organism
• Bacitracin disk (0.04 U) is applied to inoculated BAP
• After incubation, any zone of inhibition around the disk is considered as
susceptible

12. BIOCHEMICAL REACTIONS:
Bacitracin Test:
12

13. 13
BIOCHEMICAL REACTIONS:
CAMP test – (Christie Atkins Munch-Petersen)
•Principle:
• Group B streptococci produce extracellular protein (CAMP factor)
• CAMP act synergistically with staph. beta-lysin to cause lysis of RBCs
•Procedure:
• Single streak of streptococci to be tested and staph. aureus are
made perpendicular to each other
• 3 – 5mm distance was left between two streaks
• After incubation, a positive result appear as an arrowhead shaped
zone of complete hemolysis
•S. agalactiae is CAMP test positive while non-group B
streptococci are negative

14. BIOCHEMICAL REACTIONS:
CAMP test -
14

15. 15
BIOCHEMICAL REACTIONS:
Bile Esculin Test -
• Differential agar (BEA) used to isolate and identify Enterococcus
(group D streptococci) and differentiate it from other streptococci
• Bile salts are the selective component, while Esculin is the
differential component
• Must be interpreted in conjunction with gram stain morphology
• Principle:
• Enterococcus hydrolyze Esculin liberating glucose (which is used up) and
Esculetin.
• Esculetin react with ferric citrate in the medium to produce insoluble iron
salts, resulting in the blackening of the medium
• Many bacteria can hydrolyze Esculin, but only few can do so in the presence

16. BIOCHEMICAL REACTIONS:
Bile Esculin Test:
•After a maximum of
48hrs incubation,
•Less than half
darkened agar slant –
Negative result.
•Greater than half
darkened agar slant –
Positive result.
16

17. 17
BIOCHEMICAL REACTIONS:
Differentiation between alpha-hemolytic
Streptococci
•Optochin test
•Bile solubility test
•Inulin fermentation

18. 18
BIOCHEMICAL REACTIONS:
Optochin test -
•Principle:
• S. pneumonia is inhibited by Optochin reagent (<5 μg/mL) giving
an inhibition zone of ≥14mm in diameter.
•Procedure:
• BAP is inoculated with the organism to be tested and an Optochin
disc placed in the center of the plate
• After incubation at 37oC for 18hrs, carefully measure the
diameter of the inhibition zone with a ruler
• ≥14mm is positive; ≤ 13mm is negative
•S. pneumonia is positive (S); S. viridans is negative (R)

19. BIOCHEMICAL REACTIONS:
Optochin test -
19

20. 20
BIOCHEMICAL REACTIONS:
Bile solubility test -
•Principle:
• S. pneumonia produce a self-lysing enzyme capable of inhibiting its
growth and this is accelerated in the presence of bile.
•Procedure:
• Add 10 parts of the broth culture of the organism to be tested to
one part of 2% Na-deoxycholate (bile) in a test-tube
• Negative control is made by adding saline instead of bile to the
culture
• Incubate at 37oC for 15mins
• Observe and record your findings.

21. BIOCHEMICAL REACTIONS:
Bile solubility test -
• Clearing in the presence
of bile – positive;
turbidity – negative.
• S. pneumonia is soluble
in bile – positivity,
whereas
• S. viridans are insoluble
in bile – negativity.
21

22. BIOCHEMICAL REACTIONS:
Insulin fermentation -
• Useful to differentiate
Pneumococci from
other Streptcocci:
• Pneumococci ferments
inulin
22

23. IDENTIFICATION OF beta- and alpha-
HEMOLYTIC STREOTOCOCCI:
ferment
23
Not ferment

24. STREPTOCOCCAL VIRULENCE
FACTORS
24

25. STREPTOCOCCI – DISEASES:
25

26. 26
GROUP A: Streptococcus pyogenes
METABOLISM:
•Catalase – negative
•Microaerophilic
•Beta-hemolytic – due to enzymes that destroy blood cells
• Streptolysin-O:
• Oxygen labile
• Antigenic
• Streptolysin-S:
• Oxygen stable
• Non-antigenic

27. 27
VIRULENCE:
• M-protein (70 types) – major virulence factor
• Adherence factor
• Antiphagocytic
• Antigenic: induces antibodies which can lead to phagocytosis
• Lipoteichoic acid:
• Adherence factor
• Streptokinase - FIBRINOLYSIN
• Hyaluronidase – destroys CT and aids spread of the organism
• DNAase (Streptodornase)
• Anti-C5a peptidase – prevents C5a mediated phagocytic activity
• Protein F -
• Streptolysin O – also antigenic; (but Streptolysin S – not antigenic)
• Hence Anti-Streptolysin O (ASO) antibody titer rises in recent infections
• Skin infection does not induce ASO

28. 28
TOXINS:
•Erythrogenic or pyrogenic toxin (produced only by
lysogenized Group A Streptococci): responsible for
scarlet fever
•More than 4 serologically distinct toxins (Spe - A, B, C and F).
•Dick Test: once commonly used to confirm Scarlet Fever
diagnosis.
•Some strains produce pyrogenic exotoxins which act as
superantigens that superstimulate T cell leading to release
of cytokine which cause the Toxic shock syndrome.
•Toxic shock syndrome toxin (similar to, but different
from the staph exotoxin TSST-1)

29. 29
PATHOLOGY:
DIRECT INVASION/TOXIN:
•Pharyngitis:
• Red, Swollen tonsils and pharynx
• Purulent exudate on tonsils
• Fever
• Swollen lymph nodes
•Skin infections:
• Folliculitis, Erysipelas, pyoderma
• Cellulitis
• Impetigo
• Necrotizing fasciitis
•Scarlet fever: - fever and scarlet red rash on body
•Toxic shock syndrome

30. 30

31. Necrotizing fascitis
31

32. 32
PATHOLOGY:
ANTIBODY MEDIATED (Delayed):
•Rheumatic fever (may follow streptococcal pharyngitis):
• Fever
• Myocarditis: heart inflammation >> Rhuematic valvular heart disease many
years later.
• Arthritis: migratory polyarthritis
• Chorea (Sydenham’s chorea or St. Vitus dance)
• Rash: Erythema marginatum
• Subcutaneous nodules: 10 – 20 yrs after infection, may develop permanent
heart valve damage
•Acute post-streptococcal Glomerulonephritits:
• Tea or coca cola coloured urine, following streptococcal skin or pharynx
infection
• Follows skin or throat infection by Nephritogenic strains

33. 33
DIAGNOSIS:
•Gram stain: - gram positive cocci in chains
•Culture on standard laboratory media: - Growth is inhibited
by bacitracin
• S. pyogenes is the only beta-hemolytic strep which is sensitive to
bacitracin
•Pharyngitis: - Throat swab rapid antigen detection test
(RADT) is specific for S. pyogenes and immunologically
detects group A carbohydrate antigen.
• In children, RADT should be backed up by a throat culture due to
the high incidence of “strep throat” and moderate sensitivity to
RADT.

34. 34
TREATMENT:
• Penicillin G
• Penicillin V
• Penicillinase-resistant penicillin e.g Dicloxacillin: in skin infections,
where staphylococci could be the responsible organism
▪ Following rheumatic fever:
▪ Patients are placed on continuous prophylactic antibiotics to prevent repeat
strep throat infection that could potentially lead to repeat case of rheumatic
fever
▪ For invasive S. pyogenes infections, such as necrotizing fasciitis or
streptococcal toxic shock syndrome, consider adding Clindamycin.

35. 35
GROUP B: Streptococcus agalactiae
METABOLISM:
•Catalase – negative
•Facultative anaerobe
•Beta-hemolytic
•Part of normal flora:
• 25% of pregnant women carry Group B streptococci in their vagina.
• Can be transmitted to neonates during birth

36. 36
PATHOLOGY:
• Neonatal meningitis
• Neonatal pneumonia
• Neonatal sepsis
• Sepsis in pregnant women (with secondary infection of fetus)
• Increasing incidence of infections in elderly >65yrs of age and
patients with diabetes or neurological disease: causes sepsis and
pneumonia

37. 37
DIAGNOSIS:
• Gram stain of CSF or Urine: - positive cocci in chains
• Culture of CSF, Urine or Blood

38. 38
TREATMENT:
• Penicillin G

39. 39
GROUP C and G Streptococcus:
• Beta-hemolytic
• S. equi, S. canis
• Associated diseases:
• Pharyngitis, pneumonia, cellulitis, pyoderma, erysipelas, impetigo, wound
infections, puerperal sepsis, neonatal sepsis, endocarditis, septic arthritis
• Treatment:
• Penicillin, vancomycin, cephalosporins, macrolides (variable susceptibility)

40. GROUP D Streptococcus:
• 2 SUB-TYPES:
• Enterococci: (recently given their own genus
because they sufficiently differ from the
streptococci)
• S. faecalis
• S. faecium
• Non-enterococci:
• S. bovis
• S.equinus
• Enterococcus:
• Gram +ve cocci
• Singly/in pairs/short chains Enterococci
40

41. 41
METABOLISM:
• Catalase – Negative
• Facultative anaerobes
• Usually Gamma-hemolytic, but maybe alpha-hemolytic
• Positive bile esculin test

42. 42
VIRULENCE:
• Extracellular dextran helps them bind to heart valves

43. 43
PATHOLOGY:
•Sub-acute bacterial endocarditis
•Biliary tract infections
•Urinary tract infections (especially the Enterococci)
•S. bovis is associated with colonic malignancies

44. 44
DIAGNOSIS:
•Gram stain – positive cocci in chains
•Culture:
• Enterococci can be cultured in:
• 40% bile
• 6.5% Sodium chloride
• Non-enterococci can only grow in bile

45. 45
TREATMENT:
•Ampicillin, sometimes combined with an aminoglycoside
•Resistant to Penicillin G
•Emerging resistance to vancomycin
•For vancomycin resistant organisms (VRE), consider Linezolid,
Daptomycin and Nitrofurantoin.

46. 46
VIRIDANS GROUP Streptococci:
• Part of normal oral flora,
• Found in the nasopharynx and gingivial crevices
• GI tract
• Members:
• Mitis group: S. mitis, S. sanguis, S. parasanguis, S. gordonii, S. crista, S.
infantis, S. oralis, S. peroris
• Salavarius group: S. salavarius, S. vestibularis, S. thermophiles
• Mutans group: S. mutans, S. sobrinus, S. criceti, S. rattus, S. downeii, S.
macacae
• Angionosus group: S. angionosus, S. constellatus, S. intermedius

47. 47
METABOLISM:
• Catalase – negative
• Facultative anaerobes
• Mostly alpha-hemolytic; some beta- and gamma
• Resistant to Optochin
• Bile solubility - Negative

48. 48
VIRULENCE:
• Extracellular dextran – helps them bind to heart valves

49. 49
PATHOLOGY:
• Sub-acute bacterial endocarditis: caused by S. mitis group
• Dental caries (cavities): caused by S. mutans group
• Brain or Liver abscesses: caused by S. angionosus group
• Microaerophilic
• Found alone in pure cultures or in mixed cultures with anaerobes

50. DIAGNOSIS:
• Gram stain
• Culture – antibiotics may be added to inhibit growth
of contaminating bacteria
• Resistant to optochin
• Detection of group A streptococci by molecular
methods: PCR assay for pharyngeal specimens
• Antibody detection
• ASO titration for respiratory infections.
• Anti-DNAase B and Antihyaluronidase titration for
skin infections.
• Anti-streptokinase; Anti-M type-specific antibodies
50

51. 51
TREATMENT:
• Penicillin G
• Effective doses of penicillin or erythromycin for 10 days can prevent
post-streptococcal diseases.
• Drainage and aggressive surgical debridement must be promptly
initiated in patients with serious soft tissue infections.
• Antibiotic sensitivity test is helpful for treatment of bacterial
endocarditis.

52. 52
Streptococci Pneumoniae
(Pnuemococcus):
METABOLISM:
•Gram-positive lancet-shaped diplococci.
•Alpha-hemolytic (Pneumolysin is similar to streptolysin O).
•Form small round colonies on the plate, at first dome-shaped
and later developing a central plateau with an elevated rim.
•Facultative anaerobe
•Autolysis is enhanced in bile salt.
•Growth is enhanced by 5-10% CO2 – capnophilic.

53. 53
VIRULENCE:
• Polysaccharide Capsule (90 serotypes):
• Protects the organism from phagocytosis
• Highly antigenic – opsonized by antibodies specific to it
• Due to the variable serotypes, surviving an infection from one serotype does
not confer immunity over the others
• Cell wall polysaccharide
• Phosphocholine
• Pneumolysin
• IgA protease, etc.

54. 54
TOXINS:
•Pneumolysin: binds to cholesterol in host-cell membranes
(but its actual effect is unknown)
•MAJOR HOST DEFENCE MECHANISM: - Ciliated Cells of the
Resp tract and Spleen
•Loss of natural resistance may be due to:
• Abnormalities of the respiratory tract (e.g. viral RT infections).
• Alcohol or drug intoxication; abnormal circulatory dynamics.
• Patients undergone renal transplant; chronic renal diseases.
• Malnutrition, general debility, sickle cell anemia,
hyposplenism or splenectomy, nephrosis or complement
deficiency
• Young children and the elderly

55. 55
PATHOLOGY:
• Pnuemonia – pneumococcus is the most common cause of
pneumonia in adults
• Meningitis – most common cause of bacterial meningitis in adults
• Sepsis
• Otitis media (most common cause in children)

56. DIAGNOSIS:
• Gram stain: - reveals gram-positive
diplococcic
• Culture: does not grow in presence of:
• Optochin
• Bile
• Capsular polysaccharide antigen
detection
• DNA probe specific to S. pneumonia
• Virulence to mice
Pneumococcus Specific DNA probe
56

57. DIAGNOSIS:
• Positive Quellung test:
swelling when tested
against antiserum
containing anti-capsular
antibodies
• Quellung reaction:
technique used to
detect encapsulated
bacteria (such as S.
pneumonia and H.
influenza)
Quellung Antibody reaction
57

58. 58
TREATMENT:
• Penicillin G (IM)
• Erythromycin
• Ceftriaxone
• Vaccine: made against 23 most common capsular antigens.
• Vaccinate individuals who are susceptible such as elderly or asplenic
individuals (including being functionally asplenic due to sickle cell anaemia)
• Pnuemococcal conjugate vaccine - Capsular polysaccharide + Protein Carrier
• Below 2yrs
• Heptavalent and the newer 13 valent conjugated vaccines are
effective at preventing otitis media and pneumonia.

59. 59
CONCLUSION:
• STREPTOCOCCI are widely distributed in nature and some are
members of the normal flora while others are pathogenic
• Pathogenicity can be attributed in part to
• Infection by the organism, and
• Sensitization to them
• They elaborate a variety of extracellular substances and enzymes
• They are a large and heterogeneous group of bacteria impossible to
classify into one system
• Classification by various properties is key to understanding their
medical importance.