Oral Microbiology Flashcards
(36 cards)
How do viruses work?
Have nucleic acid surrounded by proteins
Invades a cell and replicates it’s genetic elements inside the cell until it dies
What are bacterial microorganisms?
Prokaryotic, unicellular organisms
What are fungi microorganisms?
Eukaryotic cells with a rigid cell wall due to chitin
3 types:
1. Yeast (unicellular)
2. Moulds
3. Mushrooms
What are 4 Different types of oral bacteria?
- Normal flora - expected bacteria to be seen (resident bacteria)
- Dental caries - caused by bacteria that weaken the enamel with acid production
- Periodontal disease - bacteria feed off soft tissue for energy
- Systemic infections - can occur in infants as bacteria cross the placenta
Why is the mouth a good habitat for microbes?
- Mucosa is warm which stimulated bacteria growth
- Tongue - has rough surface with pits for bacteria to get trapped
- Saliva - provides a food source for bacteria
How does the oral cavity try to defend against bacteria?
- Saliva - acts as a buffer, neutralises some of the acid produced by bacteria
- Gingival Cervical fluid (GCF) - contains antibodies and found in the gingival crevice
How does bacteria initially enter the oral cavity?
- After birth the oral cavity is quickly invaded by bacteria these are called the Pioneer species
These are generally gram positive bacteria, these breakdown the Carbohydrates and proteins which produces food for the new bacteria
Diversity will increase with age generally Sterptococcus is in high concentration - Bacteria can also be passed over from the mother via the placenta
How does Gram positive and gram negative bacteria differ?
- Gram positive has a larger Peptidoglycan layer (crossed linked sugars) than gram Negative bacteria
This mean when a dye is used Gram positive will be able to hold the dye due to the larger peptidoglycan layer and generally Purple = Gram positive Pink = Gram Negative - Gram positive doesn’t have an outer lipid layer where as gram negative does
How is a bacterial biofilm formed?
- Acquired Pellicle - a thin layer of salivary glycoproteins deposits on the teeth, these have protein projections (receptors) which start to adhere to bacteria
- Adhesion - Bacteria adhere with other bacteria using the receptors and carbohydrate binding proteins called lectins, at this stage acid can break down the adhesion
- Co-aggregation - biofilm is formed
What is a Biofilm?
A community of microorganism attached to a surface, it’s a multicellular ecosystem
What is plaque?
A community of dead and alive bacteria growing in a certain area
Made of
-EPS martix (extra-cellular polymeric substance - polysaccharides)
- DNA from dead and alive bacteria but also the host
What is the conditions deeper in the plaque biofilm?
- Nutrients - less nutrients deeper in the biofilms often these cell may make up the dead component
- O2 - Less o2 available deeper so often these cell are anaerobic
- PH - more acidic deeper in the biofilm due to less O2 so no respiration and fermentation happens reassessing lactic acid
What factors effect the oral flora?
- Saliva
- Gingival cervical fluid (GCF)
- PH
- Redox potential - different bacteria have different needs e.g. anaerobic don’t need O2 whereas capnophilic cells need CO2
What is commensal oral flora?
Primary colonisers of the oral cavity
E.g. Coloniser bacteria
How do bacteria grow?
Binary fission, average doubling time is 20mins -1hour
Describe a bacteria growth curve?
- Starts with a low amount of bacteria and this stays the same for a little while, this is the lag phase
- at this time bacteria are replicating DNA and making new cell walls - Exponential growth - sharpe rise in bacteria numbers
- Stationary phase - bacteria numbers plateau at a high level
- Death - Bacteria numbers steadily decreases
What is the Benefit of biofilm growth for bacteria?
- Can hide form host defences (antibodies can pierce the outer layer)! They also contain the lactamase enzyme that breaks down antibodies
- Quorum sensing, in a group the bacteria can communicate to lather behaviour/gene expression
What is Quorum sensing, and how is it used?
What - this is a way of bacteria communicating with each other using protein molecules called autoinducers, these bind to receptors on neighbouring bacteria they change the gene expression to deliver a desired group outcome
- Can be used to communicate with the body
Why is plaque bad?
- Bacteria in plaque is effective at:
1. Getting sugar into the bacterial cells
2. Catabolising the sugar into acid
3. Excreting the acid on tooth surfaces - can also store sugar when sugar levels are high
- can initiate unwanted inflammatory responses
What does Exogenous source of carbohydrate mean?
Carbohydrate source from outside e.g diet sucrose starch lactose
What does Endogenous carbohydrates mean?
Carbohydrates from inside the body e.g saliva or GCF
What process transports sugar transported into cells?
Sugar specific transport system which use ATP-dependent membrane permease
How does sugar (fructose) enter bacteria? (Using FTF)
- Sucrose sugar molecules are too large to enter the cells so need to be broken down by FTF - Fructosyl transferase
- Sucrose —-> glucose and fructan, glucose can directly enter the cell fructan is still too large and is broken down further by Fructanase
- Fructan breaks into fructose and enters cell
What is the enzyme FTF?
Fructosyl transferase - breaks down sucrose into glucose and fructan
Fructan is also known as insulin
