09/03 - Periodontal Microbiology Flashcards
How were studies on plaque formation conducted?
- adhesive tape samples from the tooth surface
- plaque grown on epoxy resin crowns worn for different time periods
- in vitro studies of attachment and aggregation between different bacterial species
- experimental gingivitis models
Early studies of oral microbiology were based on: ___ and ___.
cultivation and microscopy
What is the great plate anomaly?
when you look under a microscope, you see 100 species, but on a plate, only 50 grows; not everything you see will grow
What is the “we know what we can grow” bias?
all studies focused on cultivable species, but there are so many more species in the mouth
What approaches to study oral microbiolgy revolutionized species identification?
molecular (DNA, RNA) approaches
How many distinct oral species are there? What % have never been cultured?
- more than 700 distinct oral species
- +60% never have been cultured
- includes exotics (ex. Archea) like termite guts and other extreme environments
- fungi and viruses may also play a role in disease
What is the definition of a plaque biofilm?
organized cooperating community of organisms with specific inter-bacterial and host-bacterial interactions
What is atopic dermatitis?
“Purell disease”; children who are not exposed to bacteria when they are young begin making autoantibodies; 1st world problem (seriously!)
In the attachment stage of biofilm formation, planktonic bacteria adhere to ___ which is made up of ___ and ___. There is an alteration in ___ and ___.
- acquired pellicle
- salivary glycoproteins
- antibodies
- surface charge
- free energy
What is the difference between rapid attachers and slow attachers?
- rapid attachers: specific attachment structures (fimbrae, extracellular polymers, glycocalyx)
- no specific mechanism
How do bacterial characteristics change following attachment?
- synthesis of new outer membrane proteins
- active cellular growth
What is the difference between co-aggregation and co-adhesion during the growth phase of biofilm formation?
- co-aggregation: cell-to-cell recognition of genetically distinct cell types; mediatedby protein or glycoprotein receptors on one cell and carbohydrates on the other; all cells are suspended; “clumps” form which then attach to the pellicle
- co-adhesion: interactions between suspended and already adhering microorganisms; influenced by temperature and lactose
What two factors affect co-adhesion?
- temperature: no co-adhesion at higher than 37 degrees
- lactose: inc lactose, dec co-adhesion
What 3 things occur during biofilm maturation?
- increase in diversity
- replication and matrix formation
- ecological succession
What are the 3 categories of bacteria in ecological succession?
- tertiary colonizers: gram negative
- secondary colonizers: bridge species
- primary colonizers: gram positive and some negative
Which bacterial colonizers are usually beneficial? Which are usually pathogenic?
- beneficial: primary colonizers
- pathogenic: tertiary colonizers
Name examples of tertiary, secondary, and primary colonizers.
- tertiary: Porphyromonas gingivalis, A. actinomycetemcomitans
- secondary: F. nucleatum
- primary: S. sanguis
S. sanguis is found in large numbers in deep, active periodontal pockets. Through scaling and root planing of a deep periodontal pocket will most likely result in increased numbers of A. actinomycetemcomitans.
State whether each statement is true or false.
both are false
When a biofilm increases in thickness, what changes?
- difficulty in diffusion in and out of the biofilm
- an oxygen gradient develops
- completely anaerobic (no oxygen) conditions emerge in the deeper layers
- reverse gradients of fermentation products develop as a result of bacterial metabolism
How does the nutrition in the biofilm differ between the supragingival plaque and subgingival plaque?
- supragingival plaque: dietary products dissolved in saliva
- subgingival plaque: periodontal tissues and blood (“clavicular fluid”); bacterial hydrolytic enzymes breakdown host macromolecules into peptides and amino acids
What makes up 15-20% of a biofilm? What makes up the remaining biofilm?
- microcolonies (15-20%)
- interbacterial matrix
What are the 3 sources of the biofilm matrix?
- dead bacterial cells
- saliva
- gingival exudate
Are there voids/water channels in a bacterial biofilm? What makes up the backbone of the biofilm?
- yes
- exopolysaccharides
Compare the lower layer, loose layer, and fluid layer of the biofilm.
- lower layer: dense microbes, polysaccharide matrix, tightly bound together, steep diffusion gradients
- loose layer: irregular in appearance, extends into surrounding media
- fluid layer: stationary sublayer, fluid layer in motion, nourishes the biofilm by molecular diffusion
