(Section C: Bacteriology) Lecture 25 Flashcards
Streptococcus pyogenes
* Gram stain
* Shape
- Gram positive
- Cocci
Are S. pyogenes motile bacteria?
Non-motile
What cases of infections do S. pyogenes cause?
Zoonotic + Nosocomial
What are the 3 major categories of Streptococcus?
- α hemolytic
- β hemolytic
- γ hemolytic
α hemolytic
Partial hemolysis
β hemolytic
Complete hemolysis
γ hemolytic
No hemolysis
Streptococcus pyogenes
* Group
* Type of pathogen
* Infection type
- Group A Streptococcus
- Human-specific pathogen
- Non-invasive or Invasive
Does S. pyogenes have endospores? What type of hemolytic group is S. pyogenes?
- S. pyogenes is encapsulated
- β hemolytic
What are the types of non-invasive infections are caused by S. pyogenes?
- Streptococcal pharyngitis (Strep Throat)
- Impetigo
- Scarlet Fever (Scarlatina)
Virulence Factors of S. pyogenes
- SLO and SLS: SLS is for beta hemolysis and SLO makes it O2 sensitive
- Superantigens: Excessive activation of the immune system
- SpeB: Cleavage of bacterial/host proteins
- IgG-degrading enzyme (IdeS): Cleaves antibodies
- DNases: Degradation of neutrophil extracellular traps (NETs)
What are the types of invasive infections are caused by S. pyogenes?
- Meningitis
- Necrotizing Fasciitis (Flesh-Eating Bacteria)
- Streptococcal Toxic Shock Syndrome (STSS)
GAS Pathogenesis
- Adhesion
- Invasion
- Immune Evasion
- Dissemination
M protein
Virulence factor related to adhesion and antiphagocytosis
* Used to serroclassify S. pyogenes
How many different serotypes of M protein are there?
> 250 different serotypes of M protein
How many superantigens does S. pyogenes have?
At least 16
What reaction do superantigens cause in cells?
Activation of T-cells
* Leads to cytokine storm
* Responsible for the establishment of infections and scarlet fever
What is different about the Streptococcus pyogenes M1UK variant?
Has 27 chromosomal mutations
* Characterized by a 10 fold increase in the SpeA superantigen
What do Streptococcal DNases do?
Degrade neutrophil extracellular traps (NETs)
What is the treatment for S. pyogenes?
First course:
* 6-10 day course of amoxicillin
Second course:
* Clindamycin
* Erythromycin
* Clarithromycin
What type of antibiotics are amoxicillin?
Beta-lactams
Does S. pyogenes have resistance to any antibiotics?
No confirmed reports of Beta-lactams resistance
* Some are resistant to Erythromycin
Is there a vaccine for S. pyogenes?
No, there is currently no vaccine against GAS
What is potentially dangerous about S. pyogenes vaccines?
Potential for vaccine-induced Rheumatic Heart Disease
Rheumatic Heart Disease
* Organ affected
* Type of disease
- Heart valves (mitral or aortic)
- Autoimmune/Inflammatory
