oral microbrio Flashcards
what are the 4 main features of the oral cavity
- teeth
- mucosal surfaces
- saliva
- gingival crevice fluid
discuss the tooth as a habitat
- non shedding surface for colonisation
- have a number of surfaces
- not sterile
- bacteria accumulate in a biofilm (plaque)
- plaque is found in both health and disease
what is plaque
a biofilm of microorganisms and it forms its own micro environment
discuss the oral mucosal surfaces as a habitat
- stratified non-keratinized epithelia
- not sterile, has a population of commensal bacteria
- a barrier to deeper infection
- layers can be worn off and replaced
- houses immune cells in tissue
- if damaged can initiate inflammation
discuss saliva in terms of oral microbiology
- washes the mouth and aids in physical removal of surface material
- buffering capacity vs. acids produced
- anti-microbial factors to control microorganisms
discuss gingival crevice fluid in terms of microbiology
- GCF is serum components from the flow of serum-like fluid through the junction of the epithelium of the gingivae
- increased production of GCF during infection can lead to localised small rises in pH. this can shift types of bacteria that grow
- enzymes can contribute to tissue destruction (collagenase, elastase, trypsin)
- GCF also has antimicrobial properties (carries IgG)
list physialc (non-specific) anti microbial factors of the oral cavity
- saliva flow
- mucins and agglutinin
- sloughing of surface epithelia cells
discuss general antimicrobial (innate) factors of the oral cavity
- lysozyme = lysis of bacterial cell wall
- lactoferrins = sequestration of iron but also described to block some viral receptors and have some direct anti-bacterial and yeast activity
- sialoperoxidase = inhibits glycolysis
- antimicrobe peptides = most disrupt microbial membranes of either bacteria or yeast
**- PNMs **= patrolling of tissue and englufment and destruction of pathogens
list more specific antimicrobial facotrs (adaptive) of the oral cavity
- serum immunoglobulins/antibodies = prevent adhesion and disrupt ability to colonise
- complement = binding to and prmoting phagocytosis of pathogens
discuss dental plaque development
- initial deposition and colonisation of glycoproteins onto a clean surface
- forms microcolonies with polysaccharides, salivary proteins and glycoproteins via aerobic growth - pioneer species
- development of environment for anaerobic growth (more bacteria -> loss oxygen in environment)
- establishment of anaerobic bacteria and deposition (black pigmented anaerobes)
- mineral depositions
explain how gingivitis and periodontal disease develop
- plaque develops changing the microenvironment
- anaerobes can establish
- mineral deposition can occur
- sub gingival deposits and growth will trigger inflammation
- bacteria also secrete enzymes weakening tissue causing more damage
Where on the tooth does most bacterial growth occur?
gingical crevice
Which bacteria are the first to colonise the dental biofilm in plaque formation?
Streptococci and actinomycetes
Have adherence properties
discuss how an anaerobic microenvironment is developed and redox
- Oxygen has to diffuse into the plaque from the air.
- As O2 is used for bacterial respiration (it is reduced)
- This develops an anaerobic (reduced) ‘respiratory’ environment.
- A general rule of thumb is the more bacterial growth the more reduced / anaerobic the environment.
- Anaerobes required reduced/anaerobic conditions for their respiration.
- redox can be altered by more than just reduction of oxygen, but focus on bacteria reducing oxygen availiblity
- culture becomes more reduced unless more oxygen introduced
explain how microbial nutrition gets more complex as plaque develops
- Bacteria in a biofilm contribute to other metabolism allowing complex plaque to develop.
- Increasing numbers of bacteria reduces the redox allowing anaerobes to establish.
- First colonisers are Streptococcus and Actinomyces sp.
- Late colonisers are black pigmented anaerobes.
- External factors can alter the risk of pathological plaque
- Remove or reduce growth – reduced risk
- Increase growth rate – increased risk
list microorganisms of the oral cavity
- streptococcus
- actinomyces
- neisseria
- fusobacterium
- porphyromonas
- candida
discuss microbiology of CBA
- creamy white
- anaerobic organisms are malodorous
- some bacteria possibly haemorrhagic
- routine culture is not done
- culture reserved for recurring abscesses
- there will be a mix of gram types aerobes, facultative anaerobes and anaerobes in a CBA!
- bites may also be a route for viral infection (FIV)
