Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Firmicutes. Cell division in streptococci occurs along a single axis, so as they grow, they tend to form pairs or chains that may appear bent or twisted

1. STREPTOCOCCUS
DR. MUKTA SHARMA
PROF. AND HEAD
DEPARTMENT OF MICROBIOLOGY
SBB DENTAL COLLEGE, GHAZIABAD

2. GENERAL FEATURES
Gram’s positive cocci
 Arranged in chains
(sometimes pairs)
0.7-0.9 µm in diameter

3. Facultative anaerobes
Catalase negative
Oxidase negative

4. STREPTOCOCCUS

5. COMPARISION BETWEEN STREPTOCOCCUS AND STAPHYLOCOCCUS

7. CLASSIFICATION
 Lancefield classification-
Based on carbohydrate (C)
antigens
Rebecca Lancefield groups- 20
serotypes-- A to V
(excluding I and J).

8. GROUPABLE STREPTOCOCCI
Group A, B and D:
frequent
Group C, G, F :
less frequent

9. NON-GROUPABLE
Streptococcus pneumoniae :
pneumonia
Viridans streptococci :(S.
mutans): dental caries

10. HAEMOLYSIS REACTION -
SHEEP BLOOD AGAR
α (alpha) haemolysis
partial haemolysis
green colored zone of
inhibition

11. β (beta) haemolysis
- complete clearing zone of
inhibition
 γ (gamma) haemolysis
- no lysis of RBC

13. HAEMOLYSIS
Groups A an B are: β-
haemolytic
Group D are: α or γ-
haemolytic
S. pneumoniae and viridans
are:
α -haemolytic

14. Streptococcus
pyogenes
Group A Streptococcus

15. STREPTOCOCCUS PYOGENES
PYOGENES MEANS PUS PRODUCING
Group A streptococcal
infections affect all ages
peak incidence at 5-15
years of age

16. One of the most important
pathogens
Gram positive cocci in chains
Lancefield Serological Group A
Beta Haemolytic on blood agar

17. DISEASES CAUSED BY S. PYOGENES
Suppurative
infections
Non-suppurative
complications

18. SUPPURATIVE DISEASES
1. Respiratory infections
-Pharyngitis or sore throat
2. Skin and subcutaneous infections
-Wound infections
-Burns
-Erysipelas
-Impetigo
-Scarlet fever
-Cellulitis

19. NON-SUPPURATIVE COMPLICATIONS
1. Acute rheumatic fever
2. Acute
glomerulonephritis

21. SORE THROAT OR PHARYNGITIS
Most common of all Strep
diseases
Spread by saliva or nasal
secretions
Incubation period 2-4 days
Sore throat, slight fever (101)
Important to treat immediately to
avoid post strep diseases

22. Streptococci adhere to the
pharyngeal mucosa
By means of lipoteichoic acid
covering the surface pili
Multiplication occur
Streptococci may spread to
the surrounding tissues
leading to suppurative
complications

23. ERYSIPELAS
Acute infection and
inflammation of the dermal
layer of skin.
Painful red patches which
enlarge and thicken
Treatment -penicillin or
erythromycin

25. IMPETIGO OR PYODERMA
Found mainly in young children
Affecting face, arms, legs & other
exposed parts of the body
Localized infection of skin
Vesicles appear on the skin later
become purulent with honey
coloured crust

26. SCARLET FEVER
If the strain of S. pyogenes is
lysogenic for a particular
phage which expresses an
erythrogenic toxin the result
is Scarlet fever
Rash appears and
characteristic is the

28. Penicillin G or Erythromycin
are drugs of choice
Although the disease is self-
limiting, it is important to treat
immediately to avoid post
strep complications

29. CELLULITIS
 Infection of skin and subcutaneous
tissues
 Characterized by –
-local inflammation
-edema
-erythema
-tenderness
-fever

30. NONSUPPURATIVE COMPLICATIONS
 Rheumatic Fever-autoimmune
disease involving heart valves,
joints, nervous system.
 Acute glomerulonehritis or Bright’s
Disease-inflamatory disease of renal
glomeruli and structures involved in
blood filter of kidney. Due to
deposition of Ag/Ab complexes

31. RHEUMATIC FEVER
Most common cause of
permanent heart valve damage in
children
Exact cause not yet known but
there appears to be some
antibody cross reactivity between
the cell wall of S. pyogenes and
heart muscle

32. GLOMERULAR NEPHRITIS
Diagnosis based on history of
Strep throat and clinical findings.
Symptoms include fever, malaise,
edema, hypertension and blood
or protein in urine
Occurs in 0.5% of those having
strep throat.

33. VIRULENCE FACTORS
 Streptokinase:-
a proteolytic enzyme which lysis
fibrin
 Hyaluronidase:-
spreading factor- breakdown of
connective tissues
 DNAs:-
destroy DNA

34.  Haemolysins (leucocidins):-
responsible for rashes in scarlet
fever
 Capsule:-
antiphagocytic
 lipoteichoic acid/F protein
fimbriae
binds to epithelial cells

35. LABORATORY DIAGNOSIS
Diagnosis of acute suppurative
infection is made by culture while
in the non suppurative
complications, diagnosis is
mainly based on the
demonstration of antibodies.

36. DIAGNOSIS OF ACUTE SUPPURATIVE INFECTIONS
1. Specimens collection: swab, pus, blood
or CSF
2. Collection & transport: in sterile
container, culture immediately or sent to
the lab. In Pike’s transport medium.
3. Gram‘s staining of the smears: Gram’s
positive cocci in chains
4. Culture: inoculated on blood agar &
incubate at 37°C for 18-24 h… β
haemolytic

37. 5. Colony morphology & staining: colonies
are small (0.5-1.0 mm) pin point colonies
Circular, low convex, β haemolytic
In liquid media- granular turbidity with
powdery deposit
Hanging drop preparation shows non
motile
6. Biochemical reactions: catalase negative
7. Identification of various groups of
streptococci: gp. A are more sensitive to
bacitracin.
8. Lancefield grouping: by serologically

38. DIAGNOSIS OF NON SUPPURATIVE COMPLICATIONS
By serological tests– the routine test done
is ASO (antistreptolysin O) titration
A titre of 200 units or more is significant in
rheumatic fever
For glomerulonephritis anti DNAs B
estimation is more reliable with titre
higher than300 0r 350

39. TREATMENT & PREVENTION
 Penicillin (drug of choice)
 Erythromycin (for hypersensitive
patients)
 No vaccine is available

40. ORAL STREPTOCOCCI
 Live in oropharynx
 Mixed group of organisms
 α- haemolytic on blood agar
 Divided into 4 species groups-
 mutans gp.
 salivarius gp.
 anginosus gp.
 mitis gp.

41. 1. Mutans group-
S. mutans
S. sobrinus
S. cricetus
S. rattus
2. Salivarius group-
S. salivarius
S. vestibularis

42. 3. Anginosus group-
S. intermedius
S. anginosus
4. Mitis group-
S. sanguis
S. gordonii
S. parasanguis
S. oralis

43. • They makeup a large proportion
of resident oral flora
• One-quarter of the total
cultivable flora from
supragingival & gingival plaque
• Half of the isolates are from the
tongue and saliva
• They are transmitted from
mother to child

45. STREPTOCOCCUS MUTANS

46. CULTURE AND IDENTIFICATION
Gram’s positive cocci
In short chains
α-haemolytic
Catalase –ve
Oxidase -ve

47. PATHOGENICITY
 They causes dental caries
 But in absence of predisposing
factors, such as sucrose, they can
not cause caries
 They have ability to produce
extracellular polysaccharides in the
presence of dietary carbohydrates

48. That help binding of the
organism to enamel and to each
other
They may also cause infective
endocarditis, as a result of their
entry into the bloodstream during
intraoral surgical procedures
(tooth extraction)

49. DENTAL CARIES

50. DENTAL CARIES
 Chronic endogenous infection
 Caused by the normal oral flora
 The carious lesion is the result of
demineralization of enamel &
later of dentine, by acids
produced by plaque m/o, as they
metabolize carbohydrates.

51. TREATMENT & PREVENTION
 In patient at risk of infective
endocarditis, prophylactic
antibiotic should always be
given before dental
procedures.

52. THANK YOU