Lecture 6 - Streptococcus Flashcards
(37 cards)
What is cellulitis
Enzymes that degrade tissue that cause bacterial spreading
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 are the 4 ways to classify Streptococcus
- Hemolysis (alpha, beta or gamma)
- Lancefield (serology)
- Natural clusters
- 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
Hemolysis
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
Beta-hemolytic
Group A
Pyogenic
Classify S. agalactiae based on hemolysis, lancefield and cluster
B-hemolytic
Group B
Pyogenic
When is the lancefield classification most useful?
When classifying the B-hemolytic bacteria
3 characteristics of S. pyogenes
- B-hemolytic, Group A
- Many toxins
- Strept throat, rheumatic fever, Cellulitis
3 characteristics to S. agalactiae
- B-hemolytic, Group B
- Capsule
- Neonatal sepsis
3 characteristics of S. pneumiae
- alpha-hemolytic
- Capsule
- Pneumonia, ear infections
2 characteristics of ‘Viridans’ Strept
- alpha - hemolytic
2. Endocarditis, caries
Which two ways can Strep camouflage itself from immune system?
- Camouflage with host plasma protein - fibrinogen - to ‘hide’ from the immune system.
- 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
- Produce a C5a peptidase that inactivates this 911 molecule and thus interferes with immune signaling
- 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
- Pyogenic infection = local growth
- Toxic systemic disease
- Immune Sequelae Disease
5 examples of pyogenic infection for Strep. pyogenes
- Strept throat (5-30% carriers, 100 different M-protein strains)
- Puerperal Fever
- Pneumonia
- Skin infection
- Vascular Disease
This skin infection due to a local pyogenic infection from S. pyogenes is common in children
Impetago
