Lecture 6 - Streptococcus Flashcards Preview

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Flashcards in Lecture 6 - Streptococcus Deck (37):

What is mutualism and where is used in context when talking about the body and normal flora?

Mutualism: both organisms benefit from a relationship
The body and its normal bacterial flora like streptococcus and staphylococcus have a mutualistic relationship


What is cellulitis

Enzymes that degrade tissue that cause bacterial spreading


What are the 4 ways to classify Streptococcus

1. Hemolysis (alpha, beta or gamma)
2. Lancefield (serology)
3. Natural clusters
4. Divide genus into 6 major groups based on 16s + RNA seq.


This natural cluster is characteristic of oral flora (S. mutans), No C-CHO and many are alpha-hemolytic (green).

Viridans (S. mutans, S. mitis, S. salivarius)


This cluster is characterized as the main pathogen of Streptococcus, contains alpha and beta hemolytic bacteria as well as Group A and B.

Pyogenic (S. aureus, S. agalactiae, S. pneumonia


This cluster is found mostly in the GI and are either alpha or beta hemolytic

Enterococci (E. bovis, E. swiss, etc.)


Is the Lactic natural cluster hemolytic?

No, would be considered gamma hemolytic


What is the oldest way to classify streptococcus



What is the Lancefield classification system?

Uses serology to classify the strept based on their on their different surface C-Carbohydrates (cell wall polysaccharides)


Classify S. pyogenes based on hemolysis, lancefield and cluster

Group A


Classify S. agalactiae based on hemolysis, lancefield and cluster

Group B


When is the lancefield classification most useful?

When classifying the B-hemolytic bacteria


3 characteristics of S. pyogenes

1. B-hemolytic, Group A
2. Many toxins
3. Strept throat, rheumatic fever, Cellulitis


3 characteristics to S. agalactiae

1. B-hemolytic, Group B
2. Capsule
3. Neonatal sepsis


3 characteristics of S. pneumiae

1. alpha-hemolytic
2. Capsule
3. Pneumonia, ear infections


2 characteristics of 'Viridans' Strept

1. alpha - hemolytic
2. Endocarditis, caries


Which two ways can Strep camouflage itself from immune system?

1. Camouflage with host plasma protein - fibrinogen - to 'hide' from the immune system.
2. Producing a hyaluronic acid capsule similar to that found in host extracellular matrix


How does a bacteria attach itself to host cell to evade immune system

Facilitates colonization by using bacterial cell components such as M protein and F protein that cross-link pili to host epithelial cells


How can repeated strept throat occur?

Through strain variation to avoid the Ab. There are over 150 different strains of strep each with a different antigenic variant of the M protein


What is another name for cytolytic toxins and what do they do?

Streptolysins, they kill leukocytes and destroy clots respectively. This stops the immune system from preventing the spread of the disease


What are the two ways that Strep can reduce complement

1. Produce a C5a peptidase that inactivates this 911 molecule and thus interferes with immune signaling
2. Coating the tips of their M protein pili with host factor H, which destabalizes C3b which prevents complement and immune signaling


What are the 3 main forms of disease for S. pyogenes

1. Pyogenic infection = local growth
2. Toxic systemic disease
3. Immune Sequelae Disease


5 examples of pyogenic infection for Strep. pyogenes

1. Strept throat (5-30% carriers, 100 different M-protein strains)
2. Puerperal Fever
3. Pneumonia
4. Skin infection
5. Vascular Disease


This skin infection due to a local pyogenic infection from S. pyogenes is common in children



Two examples of Toxic Systemic Disease

1. Scarlet Fever
2. Toxic Shock-like syndrome


Describe a toxic systemic disease

Spread throughout the body not by the bacteria but by their exotoxins


2 major examples of Immune Sequelae diseases

1. Rheumatoid Fever
2. Glomerulonephritis


What type of hypersensitivity is Rheumatoid factor and Glomerulonephritis

Rheumatoid factor - Hypersensitivity II
Glomerulonephritis - Hypersensitivity III


What two diseases related to Streptococcus can be attributed to Superantigens

Scarlet Fever
Streptococcal Toxic Stress-like syndrome (STSS)


What is Type II Hypersensitivity

When an antibody binds to an epitope on the host tissue being damaged.


Explain Rheumatic fever

When an antibody made for S. pyogenes cross-reacts with heart tissue epitopes and damages the heart.


What is Type III Hypersensitivity

The result of immune-complex-induced innocent bystander tissue damage


What is an Arthus reaction

A Type III hypersensitivty that occurs in tissue spaces


What is the key to Type III Hypersensitivity

The tissue is not being damaged directly by an antibody. The tissue is an innocent bystander!


What three ways can Strep cause damage to the heart

1. Major pathogens get into blood from pharyngitis, pneumonia, a wound, etc. may land on heart tissue and cause an acute bacterial endocarditis
2. Immune response to S. pyogenes cross react and damage heart tissue
3. Patients with past heart damage are at a greater risk for sub-acute bacterial endocarditis


What is antibiotic prophylaxis

sometimes used to pre-treat, prior to invasive oral procedures, patients who have damaged hearts


How is Amoxicillin dangerous to individuals with previous heart damage

It is the most common used antibody as a prophylaxis. The b-lactam ring that is very reactive makes patients develop hypersensitivity reactions to penicillin. Most serious is Type I hypersensitivity