Streptococcus Pyogenes Flashcards
What is the major VF of Strep Pyogenes?
M protein
Characteristic of Strep. Pyogenes?
- GABHS (group A beta hemolytic streptococci)
- Gram positive cocci chain
- major cause of cellulitis
Strep Pyogenes is most common cause of what?
Bacterial cause of sore throat and immune mediated complications
Transmission of Strep Pyogenes?
Person-to-person spread by respiratory droplets (pharyngitis) or through breaks in the skin after direct contact, fomite, or arthropod vector
What does the VF Hyaluronic acid capsule do?
- produces C5a peptidase
- interferes with phagcytosis
What is the function of M protein?
hair like projections on CW which promotes adherence. Antiphagocytic and Anticomplement
What things are associated with Adherence and invasion into host cells?
Lipoteichoic acid, M protein, and F protein
Streptococcal Pyrogenic Exotoxins (erythrogenic toxin) are produced by?
Lysogenic strains of streptococci
Strep Pyrogenic Exotoxin acts as what and interacts with whom?
SPE acts as a superantigen and interacts with both macrophages and helper T cells.
Strep Pyrogenic Exotoxin is responsible for what?
Necrotizing fasciitis and streptococcal toxic shock syndrome as well as rash observed in patients with Scarlet Fever
Streptolysin S?
O2 stable –> non-immunogenic and responsible for the hemolysis in Blood agar
Streptolysin O?
O2 labile –> lyses WBC, platelets, RBC and mammalian cells. Immunogenic
what is the treatment of coronary artery disease and venous thromboses?
Streptokinase (fibrinolysin)
What is an important marker of S. pyogenes infection?
Antibodies against DNAse B
What are the Suppurative infections?
- Phayngitis
- Scarlet fever
- Pyoderma
- Erysipelas
- Cellulitis
- Necrotizing fasciitis
- Strep toxic shock syndrome
What are the non-suppurative complications/sequelae?
- Acute rheumatic fever
2. Acute glomerulonephritis
Pharyngitis or ‘Strep Throat’ clinical features are?
Petachiae, Inflamed LN, Purulent exudate
Other signs of Pharyngitis ‘Strep throat’?
- swollen “strawberry tongue”
- soft palate shows petachie
Scarlet fever is a complication of what?
Complication of pharyngitis due to pyrogenic toxin
Clinical manifestation of Scarlet fever RASH?
diffuse erythematous/sandpaper like rash on the upper chest and then spreads to the extremities with sparing of the mouth, palms and soles
Scarlet Fever clinical features?
- Strawberry tongue
- Pastia lines
- Circumoral pallor (sparring of mouth)
- Sandpaper wash
Impetigo effects what part of skin and soft tissue?
Epidermis
Erysipelas and Cellulitis effects what part of skin and soft tissue?
Dermis
Necrotizing fasciitis effects what part of skin and soft tissue?
Hypodermis
What is Pyoderma/Impetigo?
Localized purulent streptococcal infection of skin that primarily effects exposed areas.
What is the progression of pyoderma/impetigo?
Papule –> Vesicle –> Pustule –> Thick crust
The fluid in blisters for Pyoderma/impetigo is…?
Serous or “honey colored”
What is Erysipelas?
Acute inflammation of skin with lymphatic involvement. Often involves face, trunk and extremities following pharyngitis.
Patients with Erysipelas usually experience what?
localized pain, inflammation, LM enlargement, and systemic signs.
how do you distinguish cellulitis infected skin from non infected skin?
CAN NOT BE DISTINGUISHED it is not clear.
What is Necrotizing fasciitis?
Streptococcal Gangrene
Necrotizing fasciitis is caused by what factors of Strep pyogenes?
Hyaluronidase, M protein, and Hemolysin O and S
Currently Strep. Pyogenes is most frequent agent of Necrotizing fasciitis. But what other organisms may cause this?
- C. Perfringens
- S. Aureus
How does Streptococcal Toxic Shock Syndrome (STTS) occur?
S. pyogenes grows in wound –> GABHS enters blood stream, and produce superantigen –> Fever, rash, shock, etc
compared to STTS, how does TSS occur?
S. aureus grows in tampon or wound –> TSST-1 toxin enters bloodstream (no bacteremia) –> Fever, rash, shock.
What are other infections of Strep pyogenes?
- Puerpural Sepsis “childbed fever”
- Acute Endocarditis
- Pneumonia
What M types are rheumatogenic in Acute Rheumatic Fever (ARF)?
M6 and M12
Acute Rheumatic Fever is due to…?
cross-reactions between antigens of the heart and joint tissues, and the streptococcal antigen
Acute Post-Streptococcal Glomerulonephritis characteristics?
- Follows Skin or Throat infections
- Presumptive: Dark urine (hematuria)
- Definitive
Acute Post-Streptococcal Glomerulonephritis Key finding?
Loss of bowman’s space, choking or vessel lumen
Importance of Microscopic examination of smears?
Gram +ve cocci in chains seen in the pus are important, but in throat swab it is not important.
What is the selective medium for Strep. pyogenes?
Crystal Violet Blood Agar
When you do a culture on blood agar what do you see?
Small, circular, colonies with wide zone of B haemolysis.
Catalase test for Streptococci would show what result?
Negative
PYR test (pyrrolidonyl naphthalamide) would yield what result for Strep pyogenes?
Positive for Strep. Pyogenes BUT, negative for other streptococci
Bacitracin sensitivity would yield what result for Strep pyogenes?
Positive for Strep pyogenes BUT, negative for other streptococci
Serological test would provide what?
evidence for prior streptococcal infection as Abs appear after 3-4 weeks.
What is are some examples of a serological test for Streptococci?
- Antistreptolysin O (ASO) test (neutralisation test)
- Antigen Detection Test
- Rapid Latex Antigen Kit
What is Antigen detection test used for?
its a agglutination test used to see group A streptococcal antigen from throat swab.
What is the treatment for Strep Pyogenes?
Penicillin is drug of choice.
- starting therapy within 10 days prevents rheumatic fever
- no treatment for glomerulonephritis
Children 5-15 years old can get what with s. pneumoniae?
Pharyngitis
Children ages 2-5 with poor personal hygiene can get what from s. pneumoniae?
Pyoderma
What is useful for documenting recent group A streptococcal infections?
Anti-ASO test
What is the criteria to diagnose rheumatic fever?
“JONES”
- Joints: polyarthritis
- Carditis
- Nodules (subcutaneous)
- Erythema marginatum
- Syndenham’s chorea
Pharyngitis can result in what?
rheumatic fever and glomerulonephritis
Impetigo more commonly precedes what?
glomerulonephritis more than pharyngitis
ASO titer detects recent infection with what?
S. pyogenes
Strep Pyogenes causes? (Pyogenic, Toxogenic, Immunogenic)
Pyogenic: pharyngitis, cellulitis, impetigo
Toxogenic: scarlet fever, toxic-shock like syndrome, necrotizing fasciitis
Immunogenic: rheumatoid arthritis, acute glomerulonephritis
