Plaque as a biofilm Flashcards
What sites in the mouth can bacteria colonise?
- Tongue
- Teeth
- Mucosal surfaces
- Saliva
- Gingival crevice
- Periodontal pocket
- Gingival crevice / pocket fluids (serum-like)
How is the oral cavity colonised?
What are the characteristics of micro-flora?
How is the biofilm maintained?
natural acquisition / selection process not accidental
diverse / characteristic micro-flora
(NB gut organisms will not colonise mouth)
exist in harmony - microbe-host signalling to maintain ecological balance
Oral infections are usually…?
Mixed/poly-microbial in nature
No single pathogen is responsible for causing disease
What are the properties of a plaque biofilm?
– highly diverse communities
- attached to a surface
- extracellularmatrix (self-produced - usually polysaccharide)
Why is the community forming ability of biofilms essential for microbial survival?
Most free-living micro-organisms are NOT competent to grow individually Need other plaque residents to help supply nutrients, mediate attachment
What does biofilm community lifestyle allow for?
- Creation of broader range of habitats
- Metabolic diversity / efficiency – nutrient sharing or “food web”
- Protection vs competing organisms, environmental stress & host defences, anti-microbial agents
- Exchanges of genetic material
- Enhanced pathogenicity via expression of “virulence genes”
What are the sources of nutrients for biofilms?
- Endogenous
- Exogenous
Give examples of endogenous nutrients
Endogenous nutrients 1. Saliva
- proteins,peptides,
amino acids, glycoproteins
- Gingival crevicular fluid
- novel blood-derived nutrients
host proteins, vitamins, gases, cells (RBCs, leukocytes)
Give examples of exogenous nutrients
Exogenous
1. Fermentablecarbohydrate
eg sucrose
a) acid
b) sticky polymers- food storage, adhesion
Which bacteria colonise first?
What do secondary colonisers do?
What to bacteria rely upon in the absence of salivary glycoproteins?
Pioneer bacteria
Manufacture extracellular polymers, maintains biofilm structure by ‘cementing’
Rely on salivary glycoproteins
Pioneer bacteria are mainly what type of species?
mainly gram positive streptococci
What are the dominant flora in supra-gingival biofilms?
Gram-positive species: Streptococci, Lactobacillus and Actinomyces
What are the dominant flora present in subgingival biofilms?
Fusobacterium, actinomyces, p.gingivalis. p.intermedia, tannerella
Name periodontitis associated bacteria
p.gingivalis, p.micra, p.endotantalis, p.intermedia
How do bacteria interact with host receptors?
Planktonic bacteria recognise protein binding sites in the acquired pellicle
