Microbiology 2 Flashcards
Name some oral defences we have
- Saliva
- GCF
- Epithelial barrier
- Neutrophils
What does saliva contain that makes it part of our oral defence system?
- IgA
- Mucins
- Lysozymes
- Lactoferrin
- Histatins
- Defensins
- Protease
What does GCF contain that makes it part of our oral defence system?
- IgG
- IgA
- IgD
- Complement
- PMNs
- 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 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
- Entry
- Attachment
- Multiplication
- Avoiding host defences
- Causing host damage
- 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
- Invasins
- Impedin
- Agressin
- Modulin
What do adhesins do?
They confer damage by allowing pathogens to bind to host
What do invasins do?
They confer damage by facilitating pathogen entry into cell
What do modulins do?
They confer damage by affecting host immune system
What do aggressins do?
They confer damage by causing direct damage to host
What so impedins do?
They confer damage by allowing subversion of host defences
Name some cellular virulence factors
- Capsule
- Fimbriae/pilli
- Flagellum
How does the capsule act as a cellular virulence factors?
Acts as K antigen: the Immune response stimulated against capsule
Capsules help with adhesion
Capsule 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 Flagellum
- 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 in gram positive cell walls help it to invade the host?
- Helps in adhesion
- Induces cytokine release
- 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
- Resistant to host defences
- Mediates adhesion
- Promotes bone loss
- 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?
- Proteases
- Collagenases
- Fibrolysin, Hyaluronidase, Heparinise
- 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
- Leukotoxins
- 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
- Decreases the number of chemotaxis so neutrophils don’t move to the site
- They increase the number of superoxide radical causing tissue damage
What type of Aggregatibacter actinomycetemcomitans is most common in localised periodontitis?
Serotype B
What are some virulence factors of Aggregatibacter actinomycetemcomitans ?
- Potent leukotoxin which are toxic to neutrophils
- Cytolethal descending toxin which are toxic to lymphocytes
- Produce a range of adhesions
- Lipopolysaccharide and cell material which lead to bone resorption
- Produces Collagenase which breaks down the PDL
Describe Porphyromonas Gingivalis
It is an obligate anaerobe
It is a gram negative bacteria
What are some of the virulence factors of Porphyromonas Gingivalis?
- Arg Gingipain & Lys Gingipain
- Lipopolysaccharide and Fimbriae present which acts as an adhesin
- Has a capsule the helps resist host defences
- Produces Haemagglutinin which causes red blood cells to stick
- 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
- It inhibits a particular receptor (E-Selectin) which Affects neutrophil migration
- Inhibits complement activation
- Disrupts the immune regulation
- Causes Subversion of Toll like receptors (particular TLR 2 & TLR 4)
- Causes Direct cytotoxicity
- 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 and homeostasis causing perio tissue destruction
