(Section C: Bacteriology) Lecture 25

Question 1

Streptococcus pyogenes
* Gram stain
* Shape

Answer 1

• Gram positive
• Cocci

Question 2

Are S. pyogenes motile bacteria?

Answer 2

Non-motile

Question 3

What cases of infections do S. pyogenes cause?

Answer 3

Zoonotic + Nosocomial

Question 4

What are the 3 major categories of Streptococcus?

Answer 4

1. α hemolytic
2. β hemolytic
3. γ hemolytic

Question 5

α hemolytic

Answer 5

Partial hemolysis

Question 6

β hemolytic

Answer 6

Complete hemolysis

Question 7

γ hemolytic

Answer 7

No hemolysis

Question 8

Streptococcus pyogenes
* Group
* Type of pathogen
* Infection type

Answer 8

• Group A Streptococcus
• Human-specific pathogen
• Non-invasive or Invasive

Question 9

Does S. pyogenes have endospores? What type of hemolytic group is S. pyogenes?

Answer 9

• S. pyogenes is encapsulated
• β hemolytic

Question 10

What are the types of non-invasive infections are caused by S. pyogenes?

Answer 10

1. Streptococcal pharyngitis (Strep Throat)
2. Impetigo
3. Scarlet Fever (Scarlatina)

Question 11

Virulence Factors of S. pyogenes

Answer 11

• SLO and SLS: Pore formation
• 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)

Question 11

What are the types of invasive infections are caused by S. pyogenes?

Answer 11

1. Meningitis
2. Necrotizing Fasciitis (Flesh-Eating Bacteria)
3. Streptococcal Toxic Shock Syndrome (STSS)

Question 12

GAS Pathogenesis

Answer 12

1. Adhesion
2. Invasion
3. Immune Evasion
4. Dissemination

Question 13

M protein

Answer 13

Virulence factor related to adhesion and antiphagocytosis
* Used to serroclassify S. pyogenes

Question 14

How many different serotypes of M protein are there?

Answer 14

> 250 different serotypes of M protein

Question 15

How many superantigens does S. pyogenes have?

Answer 15

At least 16

Question 16

What reaction do superantigens cause in cells?

Answer 16

Activation of T-cells
* Leads to cytokine storm
* Responsible for the establishment of infections and scarlet fever

Question 17

What is different about the Streptococcus pyogenes M1UK variant?

Answer 17

Has 27 chromosomal mutations
* Characterized by a 10 fold increase in the SpeA superantigen

Question 18

What do Streptococcal DNases do?

Answer 18

Degrade neutrophil extracellular traps (NETs)

Question 19

What is the treatment for S. pyogenes?

Answer 19

First course:
* 6-10 day course of amoxicillin

Second course:
* Clindamycin
* Erythromycin
* Clarithromycin

Question 20

What type of antibiotics are amoxicillin?

Answer 20

Beta-lactams

Question 21

Does S. pyogenes have resistance to any antibiotics?

Answer 21

No confirmed reports of Beta-lactams resistance
* Some are resistant to Erythromycin

Question 22

Is there a vaccine for S. pyogenes?

Answer 22

No, there is currently no vaccine against GAS

Question 23

What is potentially dangerous about S. pyogenes vaccines?

Answer 23

Potential for vaccine-induced Rheumatic Heart Disease

Question 24

Rheumatic Heart Disease
* Organ affected
* Type of disease

Answer 24

• Heart valves (mitral or aortic)
• Autoimmune/Inflammatory