Streptococcus pyogens

Presented by
PRASHANT DAHAL
BSc. Microbiology Final Year
Sunsari Technical College, Dhara

Table of Contents
1. Introduction
2. Morphology
3. Classification scheme (Lance field classification)
4. Strep. pyogenes
4. Structure and Cultural characters
5. Biochemistry
6. Clinical significances
a. Virulence factors
b. Pathogenesis
c. Disease causing
7. Diagnosis
8. Treatment
9. Other Clinically important Streptococci

INTRODUCTION
 Streptococcus is a genus of Gram positive, anaerobic or facultative
aerobic cocci of family Streptococcaceae, within the
order Lactobacillales
 arranged as a chain or pair in a twisted manner, hence got the name
(Greek: streptos = pliant or chain; coccos = a grain or berry)
 First isolated and coined by Viennese surgeon Albert Theodor Billroth
in 1877
 non-motile (except group-D), non-sporing, capsulated
 Strong fermenter of carbohydrate releasing Lactic Acid but no gas
 More than 70 species

• Gram-positive cocci ; 0.6–1.0 𝜇m in
diameter
• arranged in long chains
• Some strains of S. pyogens and
group C are capsulated by
hyaluronic acid capsule
• Hence, may be mucoid in culture

 Broadly, Streptococci are classified by 3 systems;
1. Brown’s classification (on basis of hemolysis)
2. Lancefield grouping
3. Pathogenic potential and character

Classification is on the basis of type of hemolysis in the blood agar
viridans
Non-viridans

Lancefield Grouping
• Most widely used scheme in clinical
diagnosis
• Serological classification based on major
cell-wall carbohydrate
• Introduced by American
Microbiologist Rebecca Lancefield in
1970
• Mostly used to classify Beta-hemolytic
streptococci, but exclude Alpha-hemolytic as
NON-GROUPABLE
• twenty (20) groups A-U without I and J

Pathogenic potential and character
Grouped into 5 groups:
1. The pyogenic (pus generating) group includes most
species that are overt human and animal pathogens.
2. The mitis group includes commensals of the human oral
cavity and pharynx, except S. pneumoniae
3. The anginosus and salivarius groups are part of the
commensal microbiota of the oral cavity and pharynx.
4. The bovis group belongs in the colon.
5. The mutans group of streptococci colonizes exclusively
the tooth surfaces of man and some animals; some
cause dental caries.

 Group A beta-hemolytic streptococci
 Most important human pathogen of the genera
 causes a wide range of suppurative infections in
the respiratory tract and skin, life-threatening soft
tissue infections, and certain types of toxin-
associated reactions
 Non-motile, non sporing, oval cocci, 0.6-1𝜇𝑚
 In short chains, long in broth

 Aerobic/facultative anaerobes, 37 C, pH 7.2 –
7.4, fastidious nature, 5-10% CO2
 Culture media: enriched media are required:
BAP
 Selective media: CV-BAP, PNF(polymyxin-
neomycin-fusadic acid media)
 T. media: Pikes T.M. with CV and sodium
azide

 On BAP; small, white-gray, pinpoint, 0.5 – 1mm,
yellow, semi-transparent to opaque, matt or
glossy, mucoid if capsulated, beta-hemolysis
 On CV-BAP and PNF; same as BAP with
golden yellow color

Tests Result
Grm. Staining
Catalase
CAMP
Hemolysis
PYR
Urease
VP
6.5% NaCl growth
Motility
Ribose fermentation
Bacitracin sensitivity
Bile solubility
+ve, cocci, chain
-ve
-ve
Beta
+ve
-ve
-ve
-ve
-ve
-ve
+ve
-ve

1. Cell wall associated proteins and polymers
2. Enzymes
3. Toxins
Cell wall associated proteins and polymers
1. Capsule - prevents phagocytosis
2. Lipo-Teichoic acid(LTAs) - binds to epithelial cells
3. M proteins - Adhesin and antiphagocytic
4. F proteins – mediate attachment

Enzymes
1. Streptokinase - Breaks down the fibrin barrier
2. Deoxyribonucleases - Depolymerizes free DNA present in
the pus
3. Hyaluronidase – hydrolyze hyaluronic acid in matrix

TOXINS (most important in pathogenesis)
1. Streptococcal pyrogenic exotoxins (SPEs) - Dissolves the clot,
thrombi, and emboli
2. Streptolysin O and Streptolysin S- Lyse erythrocytes, leukocytes,
and platelets; and stimulate production of lysosomal enzymes
3. Pyrogenic exotoxins - Release large amounts of cytokines from
helper T cells and macrophages; rapidly destroy tissues

1st • ADHERENCE
2nd • INVASION
3rd • RELEASE TOXINS & ENZYMES
 Most common entry route is URT
 Most common route of infection is respiratory droplets or direct contact with
infected sores or wounds

a) Suppurative Streptococcal Disease
1. Pharyngitis (5-15% adult, 20-30% children)
2. Pyoderma

3. Erysipelas 4. Necrotizing fascitis
5. Puerperal sepsis

b) Toxin Mediated Diseases
1. Scarlet fever
2. Streptococcal toxic shock syndrome

c)Non-suppurative Streptococcal Disease
1. Acute Glomerunephritis (AGN)
2. Acute rheumatic fever (ARF)

1. Specimens; Throat swab, nasal swabs, high vaginal swabs
(puerperal sepsis), pus or pus swabs, pharyngeal secretions, blood,
CSF, joint aspirate, edge aspirate of cellulitis, skin biopsy
specimen, epiglottic secretions, bronchoalveolar lavage fluid,
thoracocentesis fluid, or abscess fluid
2. Microscopy
3. Culture
4. Biochemical test
5. Direct antigen test
6. Serodiagnosis
Done mostly for AGN and ARF

 Though responsible for severe and dangerous
diseases as already seen in pictures GOOD thing
is that it can be cured by PENICILLIN
 No resistance to PENICILLIN is known till
date
 Erythromycin and clindamycin are choice for
Penicillin allergic patient

1. S. pneumoniae
2. S. agalactiae
3. S. mutans
4. S. mitis
5. S. anginosus
6. S. sanguinis
7. S. suis
8. S. gallolyticus

Streptococcus pyogens

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