lecture 4- perio microbiology Flashcards
more than ______ distinct species of bacteria grow in the oral cavity
700
t/f: most oral microbial species have been cultured
false- 60% have never been cultured
what is the definition of a plaque biofilm?
organized cooperating community of organisms with specific inter-bacterial and host-bacterial interaction
the body develops ___________ to beneficial oral bacteria
immune-tolerance
what is Atopy? (AKA atopic dermatitis)
- the “purell” disease
- the body is not exposed to a variety of microorganisms early in life, and will start developing an immune response to its own cells
how many stages of biofilm formation are there?
5 stages
________ bacteria adhere to an acquired pellicle
planktonic
what 2 substances from human saliva are found in the pellicle
- glycoproteins
- antibodies
how do “rapid attaching” bacteria attach to the pellicle
thru specific attachment structures
- fimbriae
- extracellular polymers
- glycocalyx
how do bacterial characteristics change once they are attached to the pellicle?
- synthesis of new outer membrane proteins
- active cellular growth
___________ found on bacteria are responsible for our bodies immune response
outer membrane proteins (OMP’s)
what is co-aggregation?
cell-to-cell recognition of genetically distinct cell types
what mediates co-aggregation
1) protein or glycoprotein receptors on one cell
2) carbohydrates on the other
what is co-aggregation influenced by?
temperature
lactose (more lactose, less aggregation)
t/f: cells co-aggregate once they attach to the pellicle
False
- all cells are suspended when co-aggregating
- “clumps” form, which then attach to pellicle
co-aggregation requires at least 2 of what?
2 genetically different species
what occurs during the maturation of the biofilm?
- increase in diversity
- replication and matrix formation
- ecological succession
Porphyromonas gingivalis is a ______ colonizer. Is it gram negative or positive?
tertiary (3) colonizer
its gram negative
what are the 2nd colonizers also known as? are they usually gram negative or gram positive
bridge species
gram negative
F. nucleatum is known as a ______ colonizer
secondary (2) colonizer
AKA a bridge species
what is the role of F nucleatum in the biofilm?
- its a “prolific co-aggregator”
- binds to other bacteria
name the most prolific primary (1st) colonizer. how does it bind a pellicle?
- Streptococci species
- bind pellicle proteins from saliva
- primary colonizers can be either gram + or -
T/F: S. sanguis is found in large numbers in deep, active periodontal pockets
False- S sanguis is a beneficial species
T/F: through scaling and root planing of a deep periodontal pocket will most likely result in increased numbers of A. actinomycetemcomitans
false- A. a is a tertiary colonizer
cleaning would reduce the # of tertiary bacteria
name the tertiary, and harmful, microbes in the biofilm
1) A. actinomycetemcomitans
2) P. intermedia
3) Eubacterium species
4) T. denticola
5) P. gingivalis
6) S. flueggei
as the biofilm increases thickness, what occurs?
- difficulty in diffusion in/out of the biofilm
- an oxygen gradient develops
- completely anaerobic conditions emerge in deep layers
- reverse gradients of fermentation products develop as a result of bacterial metabolism
what is the nutritional source for supra gingival plaque?
dietary products dissolved in saliva
_______ plaque feeds of periodontal tissues and blood
subgingival
bacterial _____________ breakdown host macro-molecules into peptides and amino acids
hydrolytic enzymes
micro-colonies make up about ____% of the biofilm volume
15-20%
what are the 3 sources of the biofilm matrix?
- dead bacterial cells (form scaffold)
- saliva
- gingival exudate
what role do exopolysaccharides play in the biofilm?
they are the “backbone” of the biofilm
what are the characteristics of the lower biofilm layers?
- dense layer of microbes
- polysaccharide matrix
- tightly bound together
- steep diffusion gradient
the loose layer of the biofilm has what general characteristics?
- irregular in appearance
- extends into surrounding medium
what are the characteristics of the “fluid layer” of the biofilm?
- stationary sublayer
- fluid layer in motion
- nourishes the biofilm by molecular diffusion
cravicular epithelium will interact with the _______ layer of the biofilm
superficial
important for immune function/response
the shape of micro-colonies depends on _______ force
shear
if a micro-colony is in the form of towers or mushrooms, they are found in areas of _________
low shear force
which type of colonies are capable of oscillation?
elongated colonies
found in areas of high shear
the inter bacterial matrix of gram-positive bacteria is very ______. What causes this organization?
very fibrillar
-caused by dextrans and levans in the matrix
the inter bacterial matrix of gram-negative bacteria is very ______. What causes this organization?
very regular
- contains tri-laminar vesicles
- Filled with endotoxins and proteolytic enzymes
what type of inter bacterial matrix is filled with endotoxins and proteolytic enzymes?
gram-negative
what roles do the inter bacterial carbohydrates of the matrix play?
- energy source: dextrans, fructans
- skeleton of plaque- mutans
the ______ forms the primary attachment in sub gingival plaque
cuticle
how do the bacterial layers near the sulcular epithelium differ from tooth-attached layers? (in sub gingival plaque)
- no inter-bacterial matrix
- more spirochetes and flagellated bacteria
_____________ is necessary for succession
bacterial collaboration
streptococcus cristatus is a _______ colonizer. what metabolic characteristics does this species have?
primary colonizer
- can live with or without oxygen
- uses up oxygen when available
F. nucleatum is a _______ species. what are its metabolic characteristics?
bridge species
- robust anaerobe
- binding to strep improves survival when oxygen is present
P. gingivalis is a ______ colonizer. what are its metabolic characteristics?
tertiary colonizer
- microaerophilic, obligate anaerobe
- coaggregation essential to survival when oxygen is present
after coaggregation of bacteria in subgingival plaque, S. cristatus is carried into the gingiva by what other microbe?
S. cristatus is carried inside by F. nucleatum
what are the defensive advantages for biofilm living?
- presence of concentrated bacterial enzymes
- inter-bacterial matrix
(these factors make the microbes harder to destroy)
how are bacteria protected from external changes when living in a biofilm?
- diffusion minimal in interior regions
- antibiotic and antimicrobial resistance
- protection from friction and shearing forces
- attachment
by what mechanisms can microbes transfer information and genetic mechanisms when living in the biofilm?
- signaling (quorum sensing)
- conjugation
- transformation
- plasmid transfer
- transposon transfer
what is quorum sensing?
regulation of expression of specific genes through accumulation of signaling compounds that mediate intercellular communication
quorum sensing depends on cell ______
density
t/f: quorum sensing encourages growth of beneficial species
true
__________ produce AL-2 (a quorum sensing protein) in high levels
pathogens
t/f: biofilm bacteria are less resistant to antibiotics than planktonic bacteria
false
biofilm bacteria are 1000 to 1500 times more resistant
how does the slow growth rate of biofilm bacteria effect its sensitivity to antibiotics?
- Antibiotics depend on cell turnover for efficacy
- Slow-growers express ‘non-specific defense mechanisms’
- Slow growers make more exo-polymers
Exo-polymers retard _________
diffusion
important in biofilms ability to resist antibiotics
what is involved in the ecological concept of oral microbial diseases?
Ecological shifts lead to changes in proportions
Balance shifts in favor of “pathogens”/disease
t/f: Lack of competition in natural environments is a reason why growth of a microbe is different in nature
compared to pure culture.
false
what is different between growing microbes in nature vs. growing them in pure cultures?
Limited nutrients in natural environments.
Poor nutrient distribution in natural environments.
Not optimal temperature in natural environments
what are the clinical targets for therapy of microbes?
AI-2
Vaccines that target common resistance genes
what is the clinical significance of Translocation and transmission of bacteria in the periodontal structures?
- Periodontal probe can translocate pathogens from pockets to healthy sites
- Drug-resistant strains can translocate to neighboring teeth
- Teeth act as reservoirs for colonization of implants
Implants that fail have a microbial composition similar to _____________
periodontal disease
in regards to quarum sensing, ______ may determine switch from commensal to pathogenic community
AI-2
auto-inducer 2
