microbiol 2 Flashcards
Name some oral defences we have
- Saliva2. GCF3. Epithelial barrier 4. Neutrophils
What does saliva contain that makes it part of our oral defence system?
- IgA2. Mucins 3. Lysozymes 4. Lactoferrin5. Histatins 6. Defensins 7. Protease
What does GCF contain that makes it part of our oral defence system?
- IgG2. IgA3. IgD4. Complement 5. PMNs 6. Defensins
How is our epithelial barrier an oral defence mechanism?
Epithelial barrier cells detect invading pathogens
Describe neutrophils
Neutrophils have many nuclei & many granules stuffed with antimicrobials
What happens when neutrophils die?
If neutrophils die (lysed by bacteria) they release granules that cause damage to bacteria & host
What do organism on the tooth surface produce when they die?
They produce enzymes, metabolites, cell constituents when die These activate signalling pathways releasing pro inflammatory cytokines, chemokines and antimicrobials
In disease why does destruction occur?
Destruction occurs due to uncontrolled response to enzymes when tooth surface organisms die
Go through the stages of microbial pathogenesis
- Entry2. Attachment3. Multiplication 4. Avoiding host defences5. Causing host damage6. Releasing & spreading
What are virulence factors
Virulence factors are molecules produced by bacteria, viruses, fungi, and protozoa that add to their effectiveness to incur damage on the host cell
Name the 5 bacterial virulence factors associated with periodontal disease
- Adhesins 2. Invasins 3. Impedin4. Agressin 5. Modulin
What do adhesins do?
Enables binding to host tissues
What do invasins do?
Enables invasion of host cell/ tissue
What do modulins do?
Induces indirect damage by perturbing regulation of host defences
What do aggressins do?
causing direct damage to host
What so impedins do?
Enables avoidance of host defence mechanism(s)
Name some cellular virulence factors
- Capsule 2. Fimbriae/pilli 3. Flagellum
How does the capsule act as a cellular virulence factors?
Acts as K antigen: the Immune response stimulated against capsule Capsules help with adhesionCapsule incur resistance to killing by neutrophils & complement
How does the frimbriae act as a cellular virulence factors?
Act as receptors (adhesive characteristics)| Promotes gene transfer (resistance genes)
How does the flagellum act as a cellular virulence factors?
- Act as an H antigen which leads to an Immune response stimulated against Flagellum2. Allows mobility of the bacterium
Describe the cell wall of a gram positive bacteria
Has a thick peptidoglycan layer, teichoic and lipoteichoic acid associate with this layer
How does the thick peptidoglycan layer (Teichoic/lipoteichoic acids) in gram positive cell walls help it to invade the host?
- Helps in adhesion 2. Induces cytokine release3. Acts in aiding resistance to host defences
What do gram negative bacteria have that gram positive bacteria don’t ?
Has lipopolysaccharide in its cell wall that have a variety of virulence factors
What does the lipopolysaccharide act as in gram negative bacteria?
Acts as an O antigen
How does the lipopolysaccharide in gram negative cell walls help it to invade the host?
- Stimulates cytokine release and inflammatory response 2. Resistant to host defences 3. Mediates adhesion 4. Promotes bone loss 5. Kills macrophages
What is increased inflammation associated with?
High GCF flow Bleeding Raised pH Raised temperature Low Eh (redox potenital)
Which enzymes do bacteria produce to damage the host?
- Proteases2. Collagenases 3. Fibrolysin, Hyaluronidase, Heparinise 4. IgA & IgG proteases
What does bacteria produced proteases do?
Causes direct damage to tissue or host defences
What does bacteria produced collagenase do?
Breaks down the PDL
What does bacteria produced Fibrolysin, Hyaluronidase and Heparinise do?
Breaks down host proteins
What do bacteria produced IgA and IgG proteases do?
Breaks down immunoglobulins
Name some extracelluar virulence factors?
- Enzymes 2. Leukotoxins 3. Cyrotoxins
What do Leukotoxins do?
Kill neutrophils
What do cytotoxins do?
They are specific toxins that are released by bacteria that can lead to cell death
Name the bacteria associated with localised aggressive periodontitis?
Aggregatibacter actinomycetemcomitans
What do Aggregatibacter actinomycetemcomitan target?
The target neutrophils and causes functional abnormalities in them
How do Aggregatibacter actinomycetemcomitans cause functional abnormalities in neutrophils?
- It affects the signal pathways promoting responses of neutrophils 2. Decreases the number of chemotaxis so neutrophils don’t move to the site 3. They increase the number of superoxide radical causing tissue damage
What type of Aggregatibacter actinomycetemcomitans is most common in localised periodontitis out of the 6 ?
Serotype B
What are some virulence factors of Aggregatibacter actinomycetemcomitans ?
- Potent leukotoxin which are toxic to neutrophils2. Cytolethal descending toxin which are toxic to lymphocytes 3. Produce a range of adhesions 4. Lipopolysaccharide and cell material which lead to bone resorption 5. Produces Collagenase which breaks down the PDL
Describe Porphyromonas Gingivalis
It is an obligate anaerobe| It is a gram negative bacteria
Black-pigmented
What are some of the virulence factors of Porphyromonas Gingivalis?
- Arg Gingipain & Lys Gingipain2. Lipopolysaccharide and Fimbriae present which acts as an adhesin3. Has a capsule the helps resist host defences 4. Produces Haemagglutinin which causes red blood cells to stick5. Has extracellular vesicles which is packed with enzymes
How does Porphyromonas Gingivalis manipulate the host defences?
- Results in s local chemokine paralysis in the epithelium so neutrophils are not attracted 2. It inhibits a particular receptor (E-Selectin) which Affects neutrophil migration 3. Inhibits complement activation 4. Disrupts the immune regulation5. Causes Subversion of Toll like receptors (particular TLR 2 & TLR 4) 5. Causes Direct cytotoxicity6. Causes Citrullination which Changes the immune response
What is citrullination?
Results in the altering of protein shape by adding small group
How does P. Gingivalis act as a keystone periodontal pathogen?
P. Gingivalis elevates the virulence of the whole community by communicating with streptococci It impairs the Host immune system & the dysbiotic community inc in number, eventually disrupts tissue homeostasis causing perio tissue destruction
What is Homeostatic balance between in health?
immunostimulatory and immunosuppressive commensal organisms
Toll like receptors
Receptors on/in epithelial cells and immune cells, which detect microbial components and initiate cellular response pathways
What does A. actinomycetemcomitans leukotoxin and cytolethal distending toxin cause?
local “immune paralysis” and allow overgrowth of other organisms that increase in prevalence with disease.
Functions of P. gingivalis GINGIPAINS
Ø Cleavage of host defence peptides, complement, Ig
Ø Cleavage of cell receptors e.g. CD14
Ø Degradation of cytokines, chemokines, plasma protease inhibitors
Ø Activation of Protease Activated Receptors, IL-6 (cytokine)
Ø Activation of matrix metallo-proteinases (MMPs) and degradation of tissue inhibitors of MMPs (TIMPs)
Ø Immune evasion
Ø Nutrition (especially haem release from haemoglobin)
Allocate each of the following to category/categories of virulence factor (adhesin, invasin, impedin, aggressin, modulin)
• Collagenase- aggressin
• IgG protease- impedin, modulin
• Capsule- adhesin, impedin
• Lipopolysaccharide- adhesin, impedin, modulin
• Leukotoxin- aggressin, impedin, modulin
