streptococcus pyogenes

1. STREPTOCOCCUS
PYOGENES
ARYA LAKSHMI C R
201
GENERAL MEDICINE

2. INTRODUCTION
 Streptococcus pyogenes is a species of Gram-positive(exotoxin), aerotolerant
bacteria in the genus Streptococcus.
 These bacteria are extracellular, and made up of non-motile and non-sporing cocci
(round cells) that tend to link in chains.
 They are clinically important for humans, as they are an infrequent, but usually
pathogenic, part of the skin microbiota that can cause Group A streptococcal
infection.

3. SCIENTIFIC CLASSIFICATION
 Kingdom:Bacteria
 Phylum: Bacillota
 Class:Bacilli
 Order: Lactobacillales
 Family: Streptococcaceae
 Genus: Streptococcus
 Species: S. pyogenes
Binomial name
 Streptococcus pyogenes

5. VIRULENT FACTORS
 Virulence factors are categorized as cell wall antigens,
toxins and enzymes.
Cell wall antigens
 The cell was is composed of three layers; the inner
thick peptidoglycan layer, middle layer of group
specific C-Carbohydrate antigen and outer protein
and lipoteichoic acid layer .
 In the outer protein layer three protein antigens are
observed; M, T and R proteins
 Pilli is also present
 Capsulated(can cause diseases)

6. TOXIN
 Hemolysins: Streptococci form two hemolysins;
Streptolysin O, which is an oxygen liable streptolysin which means that the streptolysin is inactive in its
oxidized form but can get activated on treatment with some mild reducing agents and Streptolysin S
which is an oxygen stable hemolysin that is responsible for the hemolysis seen around the streptococcal
colonies on the surface of blood agar plates.
 Streptococcal Pyrogenic Exotoxin: Also known as erythrogenic toxin because it produces erythematous
reactions in the skin which is used to identify scarlet fever .
 Streptokinase: Also known as fibrinolysin, promotes the lysis of human fibrin clots by activating a
plasma precursor.
 Deoxyribonucleases: Responsible for the depolymerisation of the DNA. The Dnases are antigenically
distinct DNases A, B, C and D, out of these type B is most antigenic in human beings.

8. ENZYMES
 Nicotinamide Adenine Dinucleotidase: It acts on the coenzyme NAD and liberates
nicotinamide which is antigenic and specifically neutralized by convalescent sera .
 Hyaluronidase: It breaks down the hyaluronic acid of the tissues which favors the
spread of infection in the intercellular spaces
 Serum Opacity Factor: Some types of S. pyogenes produce lipoproteins that creates an
opacity when applied on agar gel containing horse or swine serum. It is a virulence
determinant of the organism.

9. DISEASES
 Streptococcus pyogenes is responsible
for two major respiratory tract disease.
Throat is the primary site where the
invasion occurs and the infection
occurs through respiratory droplets.
 The diseases caused are:
1. Pharyngitis
2. Scarlet Fever

10. PHARYNGITIS
 Also known as Sore throat .
 Most common streptococcal disease.
 Either in localized form or in diffused form .
 Characterized by erythema and swelling of pharyngeal mucosa with pus
secreting exudate formation.
 Children less than the age of 3 years are manifested with a syndrome of fever,
malaise and lymphadenopathy without exudative pharyngitis.
 Pharyngitis gets complicated when the infection spreads from the pharynx to
deeper tissues by direct .
 When the infection spreads through hematogenous or lymphatic routes, it
leads to diseases like sinusitis, meningitis, bacteremia etc.

11. SCARLET FEVER
 Also known as Scarlatina.
 Mainly affects children between the age of 5 years to 15 years .
 Earlier it was a very common childhood disease but now has become
rare
 It is a contagious disease that can spread even through touch.
 Mediated due to streptococcal toxins SPE-A, B, and C.

12.  Major characteristic is pharyngitis .
 Bright red rashes on skin having a sand paper like texture.
 Rashes are either due to direct action of the circulating toxin or due to
hypersensitivity reaction.
 Strawberry tongue i.e., a tongue with large red dots.
 Rashes in skin folds known as the Pastia’s lines.

13. DIAGONSIS
Specimen Collection and Transport:
 Solely depends on the site of the lesion but generally the specimens are collected from throat
swab, pus swab, exudates and blood .
 Specimens are immediately transported after collection or plated on Pike’s transport media which
consists of blood agar with crystal violet and sodium azide.
Direct Smear Microscopy:
 Gram staining of pus swab shows gram positive cocci in chain .
 In case of using throat swab direct microscopy is not much useful because in that case
Streptococcus pyogenes becomes a part of the normal flora in the sample.
Culture:
 Blood Agar: Colonies formed as small, pinpoint, circular, semitransparent and with a wide zone of
β hemolysis .
 Liquid media: Glucose, serum broth or brain heart infusion broth is used and the growth appears
as granular turbidity with powdery deposit.

14. Selective media:
 Crystal violet blood agar: 0.1% Crystal violet prevents the growth of other bacteria and promotes
only the growth of S. pyogenes .
 PNF media: Composed of horse blood agar with polymyxin B, neomycin and fusidic acid. These
antibiotics do not allow other microorganisms to grow .
Biochemical tests for identification:
Catalase test: This test helps in differentiating between catalase positive and catalase negative bacteria
where, streptococci are catalase negative.
Bacitracin sensitivity testing:
 This test helps in differentiating between group A and group B Streptococcus. The group A
Streptococcus are sensitive to bacitracin 0.04 U disk whereas the group B Streptococcus are
resistant to it. Any zone of inhibition around the disk is considered as a positive test. It can be used
as a rapid diagnostic test for Group A Streptococcus

15. CASES OF INDIA
 The lack of epidemiologic data on invasive Streptococcus pyogenes infections in
many developing countries is concerning, as S. pyogenes infections are commonly
endemic in these areas. Fifty-four patients with invasive S. pyogenes infections
were prospectively enrolled at two study sites, one in the north and one in the
south of India.
 Streptococcus pyogenes pharyngitis has a high prevalence in north India(14) ,
whereas pyoderma(Pyoderma means any skin disease that is pyogenic (has pus) )
is more frequent in south India (4). In light of invasive infection, this is a
completely neglected field in India, and the only data available in the literature are
from one retrospective study of invasive beta-hemolytic streptococcal infections
(19).

16. TREATMENT
 All the beta hemolytic group A streptococci are sensitive to penicillin G.
 Majorly sensitive to Erythromycin .
 Patients allergic to penicillin G and Erythromycin are treated with Cephalexin .
 Bacitracin is used for local application on skin lesions.
VACCINE
There is a polyvalent inactivated vaccine against several types of Streptococcus including S.
pyogenes called " vacuna antipiogena polivalente BIOL" it is recommended an
administration in a series of 5 weeks. Two weekly applications are made at intervals of 2 to
4 days. The vaccine is produced by the Instituto Biológico Argentino.

17. REFERENCES
 https://en.wikipedia.org/wiki/Streptococcus_pyogenes
 https://www.brainkart.com/article/Pathogenesis-and-Immunity---Streptococcus-
pyogenes_18019/
 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3347136/