Group A StreptococcusStreptococcus pyogenes

1. Group A
Streptococcus
Streptococcus pyogenes
Dr.T.V.Rao MD
Dr.T.V.Rao MD 1

2. 2
Preliminary Grouping of Gram Positive Cocci
Gram Positive Coccus
Catalase
Rothia
Staphylococcus
Micrococcus
PYR
+ _
+
“A Disk*
chains _
S.pyogenes
“GAS”
*A disc contains bacitracin
Enterococcus
Streptococcus sp & other
Group genera
+
Other Strep
Group genera
S R
_
See “Staph” PP
Note: SBA hemolysis as
alt to PYR?

3. 18.05.09 Phase I/ Module VII Dr Ekta 3
Overview of the Medically Important Gram Positive Cocci
Family, Genus, species Characteristics Clinical manifestations
Staphylococcaceae Cocci in cluster; catalase-positive
Staphylococcus aureus Coagulase +ve, yellow-pigmented colonies Pyogenic infections,
toxicoses
S. epidermidis Coagulase -ve, whitish colonies, normal
flora
Foreign body infections
Streptococcaceae Cocci in chains and in pairs,
catalase-negative
Streptococcus pyogenes Cocci in chains, Lancefield group A, β -
hemolysis
Tonsillitis, scarlet fever,
skin infections
S. pneumoniae Diplococci, α-hemolysis Pneumonia, otitis media,
sinusitis
S. agalactiae Chain-forming cocci, group antigen B, β-
hemolysis
Meningitis/sepsis in
neonates
S. viridans Cocci in chains, α-hemolysis Endocarditis, dental caries
Enterococcaceae In chains & pairs, α, β, or γ-hemolysis,
group antigen D, catalase -ve
Flora of intestines of
humans and animals
Enterococcus faecalis
Enterococcus faecium
Aesculin-positive, growth in 6.5% NaCl, pH
9.6
Opportunistic infections

4. Group A Streptococcal infection and
Health Care
Alexander Gordon
(1752-1799)
“... seized such women only as were
visited, or delivered, by a practitioner or
nurse, who had previously attended
patients affected by the disease….a
specific contagion, or infection....
…I could venture to foretell what women
would be affected with the disease, upon
hearing by what midwife they were to be
delivered..”
1795
Dr.T.V.Rao MD 4

5. Group A streptococcal infection and
health care
Ignaz Philipp Semmelweis
(1818-1865)
All students or doctors who enter the
wards for the purpose of making an
examination must wash their hands
thoroughly in a solution of chlorinated
lime which will be placed in
convenient basins near the entrance
of the wards. This disinfection will be
considered sufficient for this visit.
Between examinations the hands
must be washed in soap and water.
1847
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6. Group A Streptococcal infection and
health care
Louis Pasteur
(1822-1895)
”It is the nursing and medical staff who
carry the microbe from an infected woman
to a healthy one….
This water, this sponge, this lint with which
you wash or cover a wound, may deposit
germs which have the power of multiplying
rapidly within the tissue....
If I had the honour of being a surgeon....not
only would I use none but perfectly clean
instruments, but I would clean my hands
with the greatest care...”
1879
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7. Rebecca Lancefield Classifies
Streptococcus
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8. CHARACTERISTICS
 Gram positive cocci, in pairs or chains
 Catalase negative
 Facultative anaerobes
 Complex nutritional requirements (blood
or serum enriched medium)
 Ferment carbohydrates with formation of
lactic acid
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9. LANCEFIELD
CLASSIFICATION
• Group A – rhamnose-N-acetylglucosamine
• Group B – rhamnose-glucosamine
polysaccharide
• Group C –rhamnose-N-acetylglucosamine
• Group D – glycerol teichoic acid containing
alanine & glucose
• Group F – glucopyrasonyl-N-
acetylgalactosamine
Dr.T.V.Rao MD 9

10. 10
Classification - Lancefield
• Lancefield realized that all species in each “group”
generally (and conveniently) shared clinically
significant properties such as type of hemolysis,
normal host, body system or tissue where
indigenous, etc. For example:
– Group A - S. pyogenes: human upper respiratory
– Group B - S. agalactiae: human urogenital
– Group C - S. zooepidemicus: from animal
products
– Group D - S. faecalis: bile-resistant, fecal origin

11. Classification - Lancefield
• Lancefield identified many other antigens, and
proposed several Lancefield groups. Groups A, B,
C, D, F, and G were the primary groups likely from
human infections
• Lancefield later determined that viridans
Streptococcus & pneumococci did NOT possess
antigens that reacted with her antisera
• More recently, a new species, S. milleri was found
to carry A,C, F & G antigens, and display all 3
types of hemolysis.
Dr.T.V.Rao MD 11

12. 12
Lancefield Capillary Precipitation
Antibody
against a
strep group
antigen
Strep
Antigen
Extract
No Precipitate
(Negative Test)
Precipitate
(Positive Test)
Ag-Ab
interface
Ag-Ab
interface
Rabbit
Anti-
serum
Rabbit
Anti-
serum
Strep
Antigen
Extract

13. Streptococcus spp
• Gram positive, facultatively-
anaerobic
• Catalase negative, no
spores, nonmotile
• Cell division: single plane
==> chains
• Lancefield Grouping
– species-specific CHO cell
wall antigens
– groups designated A-H, K-V
– some not groupable
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14. Streptococcus pyogenes:
Microscopic appearance & Colonial morphology
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15. Structure of Streptococci
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16. Dr.T.V.Rao MD 16
Classification Based on O2
requirement
Aerobes Anaerobes
Peptostreptococci
Growth on BA
α hemolysis β hemolysis γ hemolysis
Incomplete hemolysis
(green color)
Complete hemolysis α / β / no hemolysis
Strep. viridans Strep.
pneumoniae
Enterococcus fecalis
Lancefield grouping specific
C carbohydrate Ag on cell wall
Group A – U (21 groups)
Griffith typing of Group A on MTR proteins into > 100 types

17. CLASSIFICATION TABLE
SEROLOGIC BIOCHEMICAL HEMOLYTIC PATTERN
A S. pyogenes Beta
B S. agalactiae Beta, Alpha, Gamma
C S. equimilis Beta
D S. bovis
S. faecalis
Alpha, Gamma
Alpha, Beta, Gamma
F S. milleri Alpha, Beta, Gamma
G S. milleri -do-
- S. pneumoniae Alpha
VIRIDANS S. salivarius, S. sanguis, etc Alpha, Gamma
Dr.T.V.Rao MD 17

18. PRESUMPTIVE IDENTIFICATION OF
STREPTOCOCCI
Organism Susceptibility
A P
Hydrolysis
hippurate esculin
Growth
Bile NaCl
Lysis
bile
S. pyogenes S R - - - - -
S. agalactiae R R + - - + -
Grp D
S. faecalis
S. bovis
R R
R R
- +
- -
+ +
+ -
-
-
Viridans R R
(var)
- - - - -
Pneumococcus R S - - - - +
Dr.T.V.Rao MD 18

19. Group A Streptococcus
(S. pyogenes)
 Structure:
1. Capsule – hyaluronic acid
2. Cell wall
a. protein antigens M,T,R
M protein  major virulence factor
T & R protein  no role in the
virulence
b. group specific carbohydrates – rhamnose-N-acetylglucosamine
3. Pili  consists partly of M protein & covered with
lipoteichoic acid  for attachment
Dr.T.V.Rao MD 19

20. Streptococcus pyogenes
• Streptococcus pyogenes is one of the most
frequent pathogens of humans. It is estimated
that between 5-15% of normal individuals harbor
the bacterium, usually in the respiratory tract,
without signs of disease. As normal flora, S.
pyogenes can infect when defenses are
compromised or when the organisms are able to
penetrate the constitutive defenses. When the
bacteria are introduced or transmitted to
vulnerable tissues, a variety of types of
suppurative infections can occur
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21. VIRULENCE FACTORS
1. Capsule – non-immunogenic
2. M protein – hair-like projections on the cell
wall
- major virulence factor
- promotes adherence
- antiphagocytic
- anticomplement
- type specific
Dr.T.V.Rao MD 21

22. 22
Virulence Factors of b-Hemolytic
S. Pyogenes
Produces surface antigens:
– C-carbohydrates – protect against lysozyme
– Fimbriae – adherence
– M-protein – contributes to resistance to
phagocytosis
– Hyaluronic acid capsule – provokes no
immune response
–C5a protease hinders complement and
neutrophil response
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23. Virulence Factors
• Streptolysin O: thiol-activated toxin (Groups A,C,G)
– damages membranes: RBCs, myocardial cells, PMNs
– role in intracellular survival
• Erythrogenic toxins: rash of scarlet fever
– pyrogenicity, lethal shock
– 105-fold increased sensitivity to endotoxin
• Pyrogenic exotoxin A
– contributes to streptococcal TSLS
– stimulates cytokine production by T cells
– endothelial cell damage, hypotensive shock, ischemia-based
necrosis
Dr.T.V.Rao MD 23

24. Dr.T.V.Rao MD 24
Streptococcus pyogenes – virulence factors
Antigenic – produce ASLO
Streptolysin S (SLS)
Exotoxins
Oxygen stable , non-antigenic
Damage cardiac cells
Streptolysin O (SLO) Oxygen labile
Streptococcal Pyrogenic Exotoxin (SPEs)
Manifestation of scarlet fever
Exoenzymes Streptokinase (fibrinolysin) / Streptodornase
(DNAase) / Hyalarunidase

25. Virulence Factors of b-Hemolytic
S. Pyogenes
Extracellular enzymes
1 Streptokinase –
digests fibrin clots
2 Hyaluronidase –
breaks down
connective tissue
3 DNase –
hydrolyzes DNA
25
Dr.T.V.Rao MD

26. Virulence Factors of b-Hemolytic
S. Pyogenes
4. Lipoteichoic acid – for adherence
5. Erythrogenic toxin – pyrogenic exotoxins
A,B,C
- responsible for the rash of Scarlet fever
6. Streptolysin O – lyses WBC, platelets, RBC
- immunogenic
7. Streptolysin S – non-immunogenic
- responsible for the hemolytic zones
around colonies
Dr.T.V.Rao MD 26

27. Virulence Factors of b-Hemolytic
S. Pyogenes
8. Streptokinase (fibrinolysin) – lyze
blood clots  plasminogen 
plasmin  digest fibrin & other
proteins
- facilitates spread of infection
- used in the treatment of
pulmonary emboli & coronary
artery & venous thromboses
Dr.T.V.Rao MD 27

28. Virulence Factors of b-Hemolytic
S. Pyogenes
9. DNAse (streptodornase) – depolymerizes
cell-free DNA in purulent materials
10. Hyaluronidase – spreading factor
- splits hyaluronic acid
 streptodornase & streptokinase  used in
enzymatic debridement  liquefy
exudates & facilitate removal of pus &
necrotic tissue  antibiotics gain better
access
Dr.T.V.Rao MD 28

29. Infections caused by
Streptococcus pyogenes (GAS)
• Superficial diseases
pharyngitis, skin & soft tissue infn, erysipelas,
impetigo, vaginitis, post-partum infn
• Deep infections
bacteraemia, necrotising fasciitis, deep soft
tissue infn, cellulitis, myositis, puerperal sepsis,
pericarditis, meningitis, pneumonia, septic
arthritis
• Toxin-mediated
scarletina, toxic shock-like syndrome
• Immunologically mediated
rheumatic fever, post-streptococcal GN,
reactive arthritis
Dr.T.V.Rao MD 29

30. Group A streptococcal infection
Overall disease burden
Each year
• 1.8 million new cases of
serious infection
• at least 500,000 deaths
• 110 million cases of soft tissue
infection
• 610 million cases of
pharyngitis
At least 18 million people suffer
the consequences of serious
GAS diseases
Dr.T.V.Rao MD 30

31. CLINICAL SYNDROMES
A. Suppurative Infections
1. Skin Infections
a. impetigo – superficial blisters
covered with pus or honey–colored
crust
b. erysipelas – acute superficial
cellulitis of the skin with lymphatic
involvement
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32. Pharyngitis the Prominent and
common Infection
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33. Pharyngitis and tonsillitis
33
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34. Infection of Tonsils
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35. URI continues to be common
presentation
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36. Skin lesions
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37. CLINICAL SYNDROMES
. Scarlet fever – a complication of
pharyngitis if the causative agent is
capable of producing erythrogenic toxin
 initial symptoms of pharyngitis, diffuse
erythematous rash with sparing of the
palms & soles
Circumoral pallor
“strawberry tongue”
Dr.T.V.Rao MD 37

38. CLINICAL SYNDROMES
Pneumonia –
rapidly progressive
& severe
 most commonly a
sequela to viral
infections like
influenza or
measles
Dr.T.V.Rao MD 38

39. Erysipelas
Dr.T.V.Rao MD 39

40. Streptococcus pyogenes
Necrotizing Fasciitis
• Invasive, nonTSLS
disease
– necrotizing fasciitis
(“flesh-eating
bacteria”)
– rapid development of
shock, multiple organ
system failure
– high fatality rate
Dr.T.V.Rao MD 40

41. Rheumatic Heart disease is leading
cause of Morbidity
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42. Streptococcus pyogenes
Sequellae to strep throat
• Heart valve damage
(rheumatic heart disease)
– < 3% of people with strep
throat, weeks after sore
throat
– migrating arthritis; heart
valve damage (50%), some
fatal
– recurrences common, lifelong
penicillin therapy
– shared antigen: M protein,
cardiac myosin
– attack by T cells, Ab:
inflammation, valve damage
Dr.T.V.Rao MD 42

43. Post streptococcal diseases
• Rheumatic Fever-
autoimmune disease
involving heart valves,
joints, nervous system.
Follows a strep throat
• Acute glomerulonephritis
or Bright’s Disease-
inflammatory disease of
renal glomeruli and
structures involved in
blood filter of kidney. Due
to deposition of Ag/Ab
complexes
Dr.T.V.Rao MD 43

44. CLINICAL SYNDROMES
B. Non-suppurative sequelae
1. Rheumatic fever – associated with M
types causing URI & skin infections
 fever, malaise, migratory nonsuppurative
polyarthritis, evidence of inflammation of
the heart
 carditis  leads to thickened & deformed
valves & to small perivascular granulomas in
the myocardium (Aschoff bodies)
Dr.T.V.Rao MD 44

45. 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
Dr.T.V.Rao MD 45

46. Lesions in the Heart
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47. Rheumatic Fever
• Diagnosis is based on
symptoms and is
difficult
• Occurs most frequently
between ages of 6 and
15
• US it is about 0.05% of
pop having strep
infections
• 100x more frequent in
tropical countries Dr.T.V.Rao MD 47

48. • Glomerulonephritis
– symptoms 10 days after 1˚ infection: edema
– decreased urination, hematuria, hypertension
– Ag:Ab complexes accumulate, C’ activated
– provoke inflammatory response, interferes with
normal kidney function
– young children: self-limiting
– teenagers/adults: rare permanent kidney damage,
chronic glomerulonephritis
Streptococcus pyogenes
Sequellae to strep throat or Skin Infections
Dr.T.V.Rao MD 48

49. Glomerulonephritis
2. Acute Glomerulonephritis – associated with M
types producing URI & skin infections
 particularly associated with types 12, 4, 2 &
49 which are nephritogenic
 initiated by ag-ab complexes on the
glomerular basement membrane
 hematuria, proteinuria, edema &
hypertension
Dr.T.V.Rao MD 49

50. Glomerulonephritis
• 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.
Dr.T.V.Rao MD 50

51. DIAGNOSIS
1. Microscopy
2. Culture – Bacitracin Test (Taxo-A)
3. Antigen detection tests – Enzyme-linked
immunosorbent assay (ELISA) or
agglutination tests
4. Antibody detection
 ASO titer – for respiratory disease
 antiDNAse & antihyaluronidase – for skin
infections
Dr.T.V.Rao MD 51

52. Diagnosis and treatment of Strep Throat
• Tell tale symptoms are
slight fever associated
with sore throat and
visual of pus in back of
throat
• Quick diagnostic tests
(Molecular) available
but must be confirmed
by throat swab and
growth on blood agar
(beta hemolysis)
Dr.T.V.Rao MD 52

53. Dr.T.V.Rao MD 53
Lab diagnosis – Strep. pyogenes
• Specimens: throat swab, pus,
blood
• Microscopy :Gram stain - GPC in
chains
• Culture: BA - beta hemolytic
colonies
• Identification tests -
– Catalase Negative
– Bacitracin sensitive
– Penicillin sensitive
– ASO titre / DNAase B test
B
B

54. DIAGNOSIS
1. Microscopy
2. Culture – Bacitracin Test (Taxo-A)
3. Antigen detection tests – Enzyme-linked
immunosorbent assay (ELISA) or
agglutination tests
4. Antibody detection
 ASO titer – for respiratory disease
 antiDNAse & antihyaluronidase – for skin
infections
Dr.T.V.Rao MD 54

55. Streptococci grown Blood agar
Dr.T.V.Rao MD 55

56. TREATMENT
1. Penicillin G – drug of choice
2. Erythromycin
 Antistreptococcal chemoprophylaxis in
persons who have suffered an acute attack
of rheumatic fever  Penicillin G 1.2 M units
IM every 3-4 weeks or daily oral penicillin or
oral sulfonamide
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57. • Programme created by Dr.T.V.Rao MD
for Medical and Paramedical Students in
the Developing World
• Email
• doctortvrao@gmail.com
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