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Streptococcus PyogenesGroup a streptococcus
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Group A
Streptococcus Streptococcus pyogenes
Dr.T.V.Rao MD
Dr.T.V.Rao MD 1
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?
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
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
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
Dr.T.V.Rao MD 5
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
Dr.T.V.Rao MD 6
Rebecca Lancefield Classifies Streptococcus
Dr.T.V.Rao MD 7
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
Dr.T.V.Rao MD 8
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
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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
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
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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
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
Dr.T.V.Rao MD 13
Streptococcus pyogenes: Microscopic appearance & Colonial morphology
Dr.T.V.Rao MD 14
Structure of Streptococci
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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
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
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
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
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
Dr.T.V.Rao MD 20
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
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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
Dr.T.V.Rao MD
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
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
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
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
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
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
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
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
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
Dr.T.V.Rao MD 31
Pharyngitis the Prominent and common Infection
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Pharyngitis and tonsillitis
33 Dr.T.V.Rao MD
Infection of Tonsils
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URI continues to be common presentation
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Skin lesions
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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”
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CLINICAL SYNDROMES
Pneumonia – rapidly progressive & severe
most commonly a sequela to viral infections like influenza or measles
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Erysipelas
Dr.T.V.Rao MD 39
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
Rheumatic Heart disease is leading cause of Morbidity
Dr.T.V.Rao MD 41
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
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
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
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
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Lesions in the Heart
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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
• 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
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
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
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
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
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
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
Streptococci grown Blood agar
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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
Dr.T.V.Rao MD 56
• Programme created by Dr.T.V.Rao MD for Medical and Paramedical Students in
the Developing World
Dr.T.V.Rao MD 57
