Streptococcus pyogenes, also known as group A Streptococcus, is an important human pathogen. It is a Gram-positive coccus that grows in chains. S. pyogenes can cause both suppurative infections like pharyngitis, impetigo, and necrotizing fasciitis, as well as non-suppurative sequelae including acute rheumatic fever and acute glomerulonephritis. Penicillin is the drug of choice for treating S. pyogenes infections. Prophylactic penicillin is also used to prevent rheumatic fever in individuals with a history of the disease. Group B Streptococcus and Streptococcus pneumoniae are other clinically significant streptococcal species

1. STREPTOCOCCUS
Dr. Rakesh Prasad Sah
Assistant Professor
Microbiology

2. • Streptococci are Gram positive cocci.
• Arranged in chains or pairs.
• The name streptococci (streptos meaning
twisted or coiled) was given by Billroth.

3. CLASSIFICATION:
Streptococci
Aerobes & facultative
anaerobes
Obligate anaerobes
Eg: Peptostreptococci
Beta haemolytic
Gamma haemolytic
Eg: Enterococcus group
Alpha haemolytic
Eg: Viridans streptococci
20 Lancefield groups
(ABCDEFGHKLMNOPQRSTUV)
80 Griffith types
(1,2,3,etc. up to 80)
02 requirement
Haemolysis
Serological Grouping (C carbohydrate antigen)
Group A- Streptococcus pyogens
Serological typing (M Protein)

5. Streptococcus pyogens
MORPHOLOGY:
• Gram positive
spherical or oval cocci
arranged in chains.
• Individual coccus will
be 0.5-1.0μm in
diameter.
• They are nonmotile
and nonsporing.
• Some strains have
capsule composed of
hyaluronic acid.

6. Cultural characters
 Aerobes & facultative anaerobes
 370c [22 -420c]
 Blood , serum, sugars
 Non selective media:- Sheep blood agar
 Selective media - Crystal violet Blood agar (1:500,000)
PNF medium

7. Growth on Blood agar:
• After 24 hours incubation
colonies are small, pinpoint,
translucent & zone of beta
hemolysis seen.
• Liquid media – Glucose
broth – granular turbidity &
powdery deposit

9. Biochemical reactions:
1. Catalase test: Negative

10. 2. Bile solubility test: Negative
Positive Negative

11. 3. PYR test: Positive (Pyrrolidonyl naphthylamide)
4. Ribose is not fermented.
L-Pyrrolidonyl β-
naphthylamide
p-naphthylamine
β -dimethylamino
cinnaaldehydeRed
PYRase

12. Antigenic structure:
1.Capsular hyaluronic acid: Antiphagocytic
2.Cell wall antigens:
a) Inner layer of peptidoglycan  Cell wall rigidity.
Pyrogenic & Thrombolytic
b) Middle layer of group specific C carbohydrate
c) Outer layer of protein (fimbriae) & lipoteichoic acid
 Adherence & Cytotoxicity
3.Type specific antigens:
a) M protein  adhesin, antiphagocytic, inhibits
opsonization and alternate C pathway
b) T protein
c) R protein

13. Antigenic structure of S. pyogens

14. Antigenic relationship between various
components of Str. pyogens & different
tissues
Components of Str.
pyogens
Tissues
Capsular Hyaluronic acid Human synovial fluid
Cell wall protein Myocardium
Gr A carbohydrate Cardiac valves
Cytoplasmic membrane Vascular intima
Peptidoglycans Skin antigens

15. Toxins & Enzymes
• Hemolysins
• Pyrogenic exotoxin
• Streptokinase
• Streptodornase
• NADase
• Hyaluronidase
• Lipoproteinase

16. Toxins: Haemolysins
ASO test : 200 units or >
Gr A , C , G
Streptolysin O Streptolysin S
O2 Labile O2Stable
Cytotoxic (Neutrophils, platelets)
Cardiotoxic
Leucocidal
Antigenic not antigenic
Seen in Pour plate culture Seen in Surface culture

17. Toxins
• Pyrogenic exotoxin (erythrogenic toxin)
(Erythrogenic, Dick toxin , Scarlatinal toxin / SPE )
• Dick test  toxin intradermally  erythematous rash
• Schultz Charlton reaction  scarlet fever  antitoxin 
blanching of rash
• Rashes of Scarlet fever
• A,B,C
• Superantigenes  T cells  massive release of
cytokines
• Antigenic
• Pyrogenicity, Cytotoxicity
• Enhanced S to endotoxin
• Streptococcal pyrogenic exotoxin (SPE)  fever
induction is primary response

18. Enzymes
• Streptokinase (fibrinolysin)
• Lysis of clot
conversion of plasminogen –
plasmin
• Protein in nature
• Antigenic
• Spread of infection
Use
• Early myocardial infection
• Thromboembolic disorder
• Deoxyribonuclease
(streptodornase)
• A,B,C,D
• Liquefy viscous DNA
• Anti DNAse ab in Skin
infection
• Gr A,C,G
• Use
• In Empyema (collection pus
in the cavity especially
pleural cavity)

19. Enzymes
• Nicotinamide adenine
dinucleotidase
(NADase)
• Acts on NAD
• A,C,G
• Antigenic
• leucotoxic
• Hyaluronidase
• A,B,C,G
• Spread
• Antigenic
• Serum opacity factor
[Lipoproteinase ]
Opaque to agar gel
containing horse or
swine serum

20. Other extracellular
products
• Neuraminidase
• Esterases
• Phosphatases
• Amylase
• Lipase
• N- acetyl glucosaminidase
• Beta glucoronidase

21. PATHOGENICITY:
Source of infection:
1. Patient
2. Carriers
Mode of transmission:
1. Contact: direct or indirect( through fomites)
2. Inhalation of air borne droplets
• Crowding, Schools, Camps - Favour
infection

22. Pathogenicity
Diseases caused by S. pyogens is studied
under 2 groups
1. Suppurative infections
– Respiratory infections
– Skin and soft tissue infections
– Genital infections
2. Non suppurative complications
– Acute rheumatic fever
– Acute glomerulonephritis

23. 1. Suppurative infections:
• Pyogenic infections.
• Spreads locally, along lymphatics and
through the blood stream.

24. Common suppurative infections are:
• Respiratory infections
• Sore throat
(ac tonsillitis & / pharyngitis)
• Older childrens/adults
• Cervical adenitis ,otitis media, quinsy, Ludwig's
angina, mastoiditis, meningitis
• Scarlet fever  Sore throat + rash

25. Tonsillitis Pharyngitis

26. Otitis media Mastoiditis

27. Quinsy Ludwig’s angina

28. Skin rashes in Scarlet fever

29. Skin and soft tissue infections
• Infection of wound / burn
• Lymphangitis & cellulitis
• Erysipelas
• Diffuse infection involving superficial lymphatics
• Red, swollen & indurated sharply demarcated
• Elderly
• Impetigo
• Young children
• Impetigo & streptococcal infection of scabies lesion
G.N. [in children]
• Subcutaneous infections
• Cellulitis to necrotising fascitis [mixed infection / M type 1 & 3
forming pyogenic exotoxin A]

30. Impetigo Erysipelas

31. C) Soft tissue infections:-
i) Cellulitis

32. ii) Necrotising fasciitis
• M types 1 and 3 forming
pyrogenic exotoxin A
• High fatality
• Flesh eating bacteria
• Shock, DIC
• Treatment with penicillin – not
effective
• Vancomycin – in life
threatening infections

33. Effect of flesh eating bacteria

34. iii) Soft tissue infections with some M types of
strains may sometime cause toxic shock
syndrome resembling staphylococcal TSS.

35. • Genital infections
• Puerperial sepsis
• Other pyogenic infections
• Abscesses – brain , lungs , liver & kidneys
• Pyemia , septicemia

36. 2. Non suppurative complications:
• It is also called as post streptococcal
complications
• Non suppurative complications of
S.pyogens occur 1-4 weeks after the acute
infection.
• The organism may not be detectable when
these complications set in.

37. • These complications are believed to be the
result of hypersensitivity to some
streptococcal components.
• The complications are-
1. Acute rheumatic fever
2. Acute glomerulonephritis

38. 1. Acute rheumatic fever: It occurs after repeated
sore throat caused by S. pyogens.
Mechanism of pathogenesis:
During primary infection antibodies will be produced
against some streptococcal antigen.
Since streptococcal antigen has similarity with cardiac
tissue antigen, the antibodies will cross react with
cardiac tissue antigen causing destruction.
Leads to clinical symptoms such as carditis, fever and
malaise.

39. 2. Acute glomerulonephritis: It follows after skin
infection caused by S. pyogens nephritogenic types.
Mechanism of pathogenesis:
During skin infection caused by nephritogenic types of
S. pyogens, the antibodies will be produced against
cell membrane antigen.
These antibodies cross react with glomerular
basement membrane antigen causing destruction.
Leads clinical symptoms such as proteinuria,
haematuria & hypertension.

40. Non –Suppurative Complications
Ac rheumatic fever Ac
Glomerulonephritis
Site of infection Throat Throat / Skin
Prior Sensitisation Essential Not necessary
Serotype of Str
pyogens
Any Pyoderma types 49,
53-55,59-61 &
Throat inf types 12, 1
Immune response Marked Moderate
‘C’ level unaffected Lowered

41. Ac rheumatic fever Ac
Glomerulonephritis
Repeated attacks Common Absent
Course Progressive / Static Spontaneous
resolution
Prognosis Variable Variable Good
Hereditary tendency Present Not known
Penicillin prophylaxis Essential Not indicated
Non –Suppurative Complications

42. Lab Diagnosis
• Ac Suppurative Infections : by culture
• Nonsuppurative complications :
Demonstration of ab

43. LABORATORY DIAGNOSIS:
A) In acute suppurative infection
Specimens to be collected:
• Throat swab,
• Pus,
• Tissue material,
• Blood,
• Swab from nose for detection of carriers.
Transport media: Pike’s medium

44. I) Direct Microscopy:
• Direct microscopy with
Gram stained smear is
useful in case of pus &
CSF, where cocci in
chains are seen.
• This is of no value for
specimen like sputum &
genital swabs where
mixed flora are
normally present.
Methods of examination:-

45. c) Gram’s staining:
Smears are
examined from the
culture plate and
reveals Gram
positive cocci in
chains.
II) Culture:
a) Media used:
b) Cultural Characteristics:

46. d) Biochemical reactions:
e) Bacitracin (1 unit/ml) sensitivity test:
S. pyogens is sensitive.

47. Lab Diagnosis
 Lancefield grouping
 Grown in Todd Hewitt broth
 Extraction of C carbohydrate – HCL /
formamide /autoclaving /enzyme
(streptomyces albus)
 Precipitation with sp antisera
 Antigen detection test ELISA /Agglutination
test [throat swab]

48. Lab Diagnosis
Nonsuppurative complications
 Rheumatic fever
 ASO titre (200 U / more)
 Ac G.N.
 anti DNAse B titre (300/350 )
[retrospective diagnosis of streptococcal pyoderma]
 antihyaluronidase
 Streptozyme test [[Passive slide
haemagglutination test ]] : screening test for
all types of streptococcal infection

52. • Other Hemolytic Streptococci – also cause human
diseases
45% - Group A
10-15% - Group B
10-15% - Group C
25% - Group G
5% - Group F

53. Group B Streptococci:
• Str. Agalactiae (Commonsal in female genital tract)
• Imporatant cause of neonatal meningitis, septicaemia
• Infection acquired during birth from birth canal
• Identified by CAMP (Christine Atkins Munch Peterson)
reaction. CAMP factor enhances the Beta hemolysis caused
by Staphylococcus
• Early onset – Septicaemia, Meningitis,
Pneumonia
• Late onset – less severe
• Adults infection – Septic abortion,
Puerperal sepsis

54.  Group D – Str.faecalis
• Normally present in intestine, saliva, genital tract, wound
infection in perineumal skin & subcutaneous tissue
• Causes UTI, wound infections, SABE, peritonitis, abscess, biliary
tract infection.
• Enter blood circulation - Bacteremia - Lodge on damaged heart
valves.
septicaemia - Lodge in Urinary tract
• It occurs in pairs, grows on MacConkey agar, ferment mannitol,
sucrose, esculin, black colonies on Potassium tellurite blood
agar, 6.5% NaCl, 40% bile at 45ºC.
 Str.viridans:
• Normally present in human mouth & throat, Oppurtunistic
pathogen
• In persons with valvular disease of heart, they can cause SABE
after tooth extraction

55.  Procedure:
• Enter blood circulation & lodge on damaged heart valves & produce
SABE.
• Dental Caries – Str. mutans breaks down sucrose into acid & dextran
• Acid damages dentine. Dextran binds food debris, efri cells, mucus bacteria
to form dental plaques, caries

56. TREATMENT:
• Penicillin G is the drug of choice.
• In patients allergic to penicillin; erythromycin
or cephalexin is used.
• Antibiotics have no effect on established
glomerulonephritis & rheumatic fever.

57. PROPHYLAXIS:
• Prophylaxis is indicated only in the prevention
of rheumatic fever.
• It is done by long term administration of
penicillin in children who have developed
early signs of rheumatic fever.
• Antibiotic prophylaxis is not useful in case of
glomerulonephritis.

59. • Other Hemolytic Streptococci – also cause human
diseases
45% - Group A
10-15% - Group B
10-15% - Group C
25% - Group G
5% - Group F

60. Group B Streptococci:
• Str. Agalactiae (Commonsal in female genital tract)
• Imporatant cause of neonatal meningitis, septicaemia
• Infection acquired during birth from birth canal
• Early onset – Septicaemia, Meningitis, Pneumonia
• Late onset – less severe (Osteomyelitis, arthritis, conjunctivitis,
respiratory infection, endocarditis & peritonitis.)
• Adults infection – Septic abortion, Puerperal sepsis
Identified by CAMP (Christine Atkins Munch Peterson) reaction. CAMP
factor enhances the Beta hemolysis caused by Staphylococcus

61. Clinical significance:
1. Infection in neonates: 2 types
a. Early onset disease- Occurs during first
week of life.
Source of infection- Vagina of the mother &
infection is acquired during birth.
Clinical symptoms- Septicemia, meningitis &
pneumonia.

62. b. Late onset disease- Occurs during 2nd & 12th
week of life.
Source of infection: It usually acquired from the
hospital environment.
Clinical symptoms- Osteomyelitis, arthritis,
conjunctivitis, respiratory infection, endocarditis
& peritonitis.
2. Infection in adult: It causes bacteraemia,
sepsis , wound infection, septic abortion &
puerperal sepsis.

63. Laboratory diagnosis:
Specimens collected: Blood, CSF & exudates
from lesions.
Methods of examinations:
1. Detection of antigen in clinical samples.
2. Direct microscopy by doing Gram’s smear.

64. 3. Culture- Blood agar is used for culture.
4. Identification-
a. Small β-haemolytic colonies on blood agar
b. Gram staining
c. Catalase test- Negative

65. d. Hippurate hydrolysis- Positive

66. • FIG. 2. CAMP test for the identification of Streptococcus
agalactiae (group B). (A) Streptococcus (group B) shows
a positive CAMP reaction. (B) Streptococcus pyogenes
(group A) shows a negative reaction when inoculated at
a right angle to (C) Staphylococcus aureus.

69. f. Lancefield sero grouping is done for
confirmation.
Treatment: Penicillin is used.

70. Group D Streptococci:
Classified into 2 groups-
1. The enterococcus group- which have
been reclassified as a separate genus called
Enterococcus, containing- E. faecalis,
E. faecium & E. durans.
2. Non enterococcal group- containing
S. bovis & S. equinus

71. ENTEROCOCCUS
• Normal inhabitants of human intestinal tract.
• Possess some distinctive properties like-
1. They grow in 40% bile,
2. They resist pH till 9.6.
3. They grow in 6.5% NaCl solution,
4. They grow at 45ºC can withstand up to 60ºC for
30 minutes.
5. They grow in 0.1% methylene blue milk.
6. PYR test positive
7. Resistant to SXT

72. Morphology:
• Enterococci typically
appear as pairs of
oval Gram positive
cocci.
• The cells in a pair
arranged at an
angle to each other.

73. Clinical significance:
Source & mode of infection:
1. Endogenous-from colonized site.
2. Exogenous-through direct or indirect contact.
Common infections:
1. Urinary tract infection,
2. Bacteremia,
3. Wound infection,
4. Biliary tract infection,
5. Sub acute bacterial endocarditis.

74. Laboratory diagnosis:
Specimens collected: Urine, blood, pus &
exudates.
Methods of examination:
1. Direct microscopy- by doing Gram’s smear.
2. Culture- Blood agar and MacConkey’s agar is
used.

75. 3. Colony morphology-
i) On blood agar small non-haemolytic colonies
are seen but some strains may show α or β
haemolysis.
ii) On MacConkey’s agar it produces pink
colour colonies.
4. Identification-
i) Gram’s smear
ii) Catalase test- Negative

76. iii) Biochemical tests-
• It ferments mannitol, sucrose & sorbitol.
• Bile esculin test- positive (aesculin 
aesculetin + ferric citrate  Black ppt)
+-

77. Treatment:
• Strains resistant to penicillin & other
antibiotics occur frequently.
• Vancomycin is the alternative drug to
penicillin.
• Vancomycin resistant is also seen.

78. DIFFERENT GROUPS OF STREPTOCOCCI
Lancefield
group
Species / common
name
Diagnostic tests Diseases caused
A Str. pyogenes Bacitracin sensitive ,
PYR positive , ribose
not fermented
URT inf., skin inf. , ac.
RF ,
ac.glomerulonephritis
B Str. agalactiae CAMP test - + ve ,
Hippurate hydrolysis
+ve
Neonatal septicemia &
meningitis
C Str. equisimilis Ribose fermented ,
trehalose fermented
Pharyngitis ,
endocarditis
D 1) Enterococcus sp
2) non- enterococci
Growth 6.5% Nacl
No growth 6.5% Nacl
UTI, wound inf
Genitourinary inf
Not typed Viridans Str. Optochin resistant Endocarditis , dental
caries