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
discuss distribution of flora in the oral cavity
- plaque formation on teeth is not uniform
- depends on the degree of protection from oral removal of forces and gradients of biological factors from the host
Which anaerobic bacteria are established onto developed plaque?
- Porphyromonas
gram -ve, anaerobic rods
What changes in plaque development allows more bacteria to colonise?
Nutrition varies as flora changes
Change in plaque pH
what factors affect plaque development
- age (acquisition continues with age)
- changes of microbiology
- diet change
- tooth eruption
- adhesion factors
what is dental plaque made of
- bacteria
- proteins
- cations
- immunoglobulins
what is calculus
- mineralised phosphates deposited around bacteria
- can occure subgingival or supragingival
- presence increases with age
- thise close contact with periodontal pathogens can lead to stimulation bone resorption
- once formed a lot of force is required to remove it
- dental products may include compounds to reduce mineralisation
phosphate containing ions:
- apatite (Ca and other ions including F, Cl and Br)
- brushite (Ca)
- whitlockite (Mg and Ca)
what is dental caries (decay) and how does it occur
- non-specific due to increased acids causing local demineralization
- specific immune mediated where odontoclast over-activity occurs (eg. FORL)
discuss the steps of FORL
- very specific feline dental issue
- chronic acumulation of microorganisms
- endothelial end epithelial production of cytokines
- initiation and stimulation of odontoclastic activity
- stem cells attracted to the gingival sulcus area by the cytokines
- insteada forming into macrophages the stem cells become clast cells
- clast cells dissolve mineralised tissue
- clast cells multinucleated giant dissolve the tooth tissue
list microorganisms of the oral cavity
- streptococcus
- actinomyces
- neisseria
- fusobacterium
- porphyromonas
- candida
discuss oral streptococcus
- gram positive
- facultative anaerobes
- fastidious (requires enriched media)
- range of haemolytic activities
- found in all animals
- linked to a number of diseases (bacterial species and site dependent)
- ## can also cause opportunistic infection
discuss oral actinomyces
- gram positive
- slow growth rate
- colonise mucous membranes
- opportunistic pathogen particularly oral cavity infections
- colonies form branched networks of hyphae (easily confused with fungi)
- in rare cases these bacteria can cuase actinomycosis
- genera is common in the environment
discuss oral neisseria
- gram negative
- diplococci
- this genera colonize the mucosal surfaces of many species
- common isolate from oral cavity of dogs and other species
- requires oxygen but some prefer increased CO2
discuss oral porphyromonas
- gram negative
- anaerobic
- rod shaped bacteria
- produces pophyrin pigments
- not zoonotic
discuss link between cat bite abscesses and oral microbiology
- bacteria and cell debris from oral cavity (teeth/saliva) get trapped in wound
- defensive reaction of the tissue designed to prevent spread of infection occurs
- inflammatory response begins
- white blood cells arrive
- increased blood flow
- abscess formation = core of pus surrounded by granulation tissue
clinical signs of cat bite abscesses
- pyrexia
- results in inappetance and depression
- if spreads to deeper structures = bone/muscle/CNS signs
- abscess may not be apparent immediately
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)
discuss mycological infections of the mouth
- yeasts are common part of oral flora and other mucous membranes
- out of 200 candidia species, only 2 are opportunist infections: albicans and tropicalis
- candidiasis is mainly a disease of keratinized epithelium
- infections observed in immunosuppressed or where there are other chronic oral diseases
- infections appear: white pseudomembranous covering greyish plaques with some ulceration
what is lumpy jaw
- caused by actinomyces bovis
- mucosal commensal invades tissue through breaks in the lining of the mouth. damage due to rough forage or sharp tooth damage
- pathology = tumor like swellings that slowly develope into immovable hard swellings on the upper and lower jaw of cattle, commonly at the central molar level.
- lumps consist of a honeycombed masses of thin bone filled with yellow pus
- advanced cases can develop and discharge small amounts of sticky pus containing gritty yellow granules
- most common treatments are iodine therapy or tetracyclines
what is wooden tongue
- caused by actinobacillus lingieresii (gram -ve facultative anaerobe)
- commensal of mucous membranes invades through breaks in the lining of the mouth due to abrasion by rough feed
- pathology: sudden onset with the tongue becoming hard, swollen and painful
- chronic pyograunulomatous inflammation of the soft tissue
- infections is limited in most cases to the soft tissue of the tongue and lymph nodes of the tongue
what is fusobacterium necrophorum
- gram negative obligate anaerobic
- pleomorphic bacterium
- found in the alimentary tract of animals and resp tract of cattle
- infections involve mucous membranes and underlying tissues of the oral cavity epithelium in calves and pigs, less common in goats
- to establish infections usually require injury that breaches an intact epidermal layer
- self limiting
- initially animals may show signs of not drinking
- involve several toxins: leucocidins, haemolysin and cytoplasmic toxin
