Periodontal Microbiology Flashcards
Explain the experimental gingivitis model.
Human volunteers with clean teeth and clinically healthy gingival tissues abolished oral hygiene practices leading to plaque deposits covering almost all tooth surfaces and consequently developing a generalized marginal gingival inflammation.
What are two early studies done in oral microbial research?
- cultivation
2. microscopy
The ___ ___ Anomaly is the difference between what is seen on microscopy versus what is grown on a plate (cultivation).
Great Plate
A ___ is an organized cooperating community of organisms with specific inter-bacterial and host-bacterial interactions.
biofilm
What occurs during the first and second stages of biofilm formation?
- Free-swimming bacterial cells align on a surface, arrange themselves in clusters and attach.
- the collected cells begin producing a gooey matrix
Which stage are the following?
A. The cells signal one another to multiply and form a microcolony.
B. Some cells return to their free-living form and escape, perhaps to form new biofilms.
C. Chemical gradients arise and promote the coexistence of diverse species and metabolic states.
A - stage 3
B - stage 5
C - stage 4
Planktonic bacteria adhere to the ___ ___, which is composed of salivary ___ and ___. This film alters the surface ___ and ___ energy, which in turn increases the efficiency of bacterial ___.
acquired pellicle; glycoproteins; antibodies; charge; free energy; adhesion
T/F. Bacteria vary in their attachment ability.
True.
___ attachers possess specific attachment structures (fimbriae, extracellular polymers, glycocalyx), which enable them to attach upon contact.
Rapid
T/F. Slow attachers have specific mechanisms allowing them to attach.
False, slow attachers have NO specific mechanism
How does bacterial characteristic change following attachment?
After attachment, bacteria change their phenotype.
- synthesis of new outer membrane proteins
- active cellular growth
___ is cell-to-cell recognition of genetically distinct cell types mediated by protein or glycoprotein receptors on one cell and carbohydrates on the other.
Co-aggregation
T/F. In co-aggregation, all cells are suspended and once a ‘clump’ forms attachment to pellicle occurs.
True.
___ interactions between suspended and already adhering micro-organisms.
Co-adhesion
Co-adhesion is influenced by temperature (no co-adhesion > ___ degree) and lactose ( increased lactose = ___ co-adhesion).
37; decreased
During biofilm fomation maturation, there is an ___ in diversity, ___ and ___ formation, and ___ succession.
increase; replication; matrix; ecological
Define ecological succession.
Increase in type and number of species.
Primary colonizers are gram ___ (Strep) and ___ (Actino) that bind pellicle proteins from saliva. Secondary colonizers (gram ___) are bridge species (f. nucleatum) and bind other bacteria. Tertiary colonizers (gram ___) are not normally present in enough numbers to be pathogens.
positive; negative; negative; negative
T/F. As the biofilm increases in thickness, there is no difficulty in diffusion in and out of the biofim as a sodium gradient develops.
False, As the biofilm increases in thickness, there IS difficulty in diffusion in and out of the biofilm and an OXYGEN gradient develops.
Completely anaerobic ( NO ___) conditions emerge in the deeper layers and a reverse gradient of ___ products develop as a result of bacterial metabolism.
oxygen; fermentation
How does a supragingival plaque get nutrition? Subgingival?
SUPRA - dietary products dissolved in saliva
SUB - periodontal tissues and blood
What is used to breakdown host macromolecules into peptides and amino acids?
bacterial hydrolytic enzymes
The biofim is made up on ___ (15-20% volume) + interbacterial ___.
microcolonies; matrix
What are the three sources of matrix?
- dead bacterial cells
- saliva
- gingival exudate
T/F. There is a presence of voids or water channels in the bioflim.
True.
What makes up the backbone of the biofilm?
exopolysaccharides
The lower layer of the biofilm includes a dense layer of ___ with a ___ matrix that is tightly bound together with steep ___ gradients.
microbes; polysaccharide; diffusion
The ___ layer of the biofilm is irregular in appearnce and extends into the surrounding medium.
loose
The ___ layer of the biofilm is a stationary sublayer with fluid in motion that nourishes the biofilm by ___ diffusion.
fluid; molecular
What determines the shape of micro-colonies?
It depends on shear force due to the passage of fluid over the biofilm
T/F. If the shape of a micro-colony is in the form of a tower or mushroom, then it is under high shear force. Whereas, elongated colonies capable of oscillation are under a low shear force
False, at low shear force, colonies are shaped like towers or mushrooms, while at high shear force, the colonies are elongated and capable of rapid oscillation.
The interbacterial matrix is highly variable. Gram positive matrix is very ___ due to dextrans and levans.
fibrillar
Gram negative matrix is very regular because it contains ___ vesicles filled with ___ and proteolytic enzymes that are probably involved in ___.
tri-laminar; endotoxins; adherence
Interbacterial carbohydrates have an energy source from ___ and ___. The skeleton of plaque is ___.
dextrans; fructans; mutans
What forms between the subgingival plaque and the tooth?
Cuticle, an electron dense organic material. This structure is similar to supragingival plaque
T/F. It is unsure whether the cuticle originated from an epithelial attachment, crevicular fluid, or was secreted by adjacent epithelium. BUT its location in the subgingival area makes it unlikely that salivary constituents contributed to its formation.
True.
Is the bacterial layers near the sulcular epithelium different from tooth-attached?
Yes, there is no definite inter-microbial matrix and more spirochetes and flagellated bacteria that are capable of motility are present.
Streptococcus ___ is a ___ species that can live with or without O2. It uses up O@ when available.
cristatus; facultative
Fusobacterium ___ is a robust ___ that binds to Strep and improves survival when O2 is present.
nucleatum; anaerobe
___ gingivalis is a ___, ___ anaerobe whose coaggregation is essential to survival when O2 is present.
Porphyromonas; microaerophili, obligate
F. ___ invades epithelial cells for protection but S. ___ does not invade cells. What happens after co-aggregation?
nucleatum; cristatus
S. cristatus is carried inside by F. nucleatum
Defense is an advantage to living in a biofilm. There is a presence of concentrated bacterial ___ and a ___ matrix.
enzymes; interbacterial
When living in a biofilm, bacteria are protected from external changes because ___ is minimal in interior regions, antibiotic and antimicrobial resistance, protection from ___ and ___ forces, and ___.
diffusion; friction; shearing; attachment
How can bacteria transfer info and genetic material while living in a biofilm?
signaling (quorum sensing) conjugation transformation plasmid transfer transposon transfer
___ ___ is the regulation and expression of specific genes through accumulation of signaling compounds that mediate intercellular communication.
Quorum sensing
What does quorum sensing depend upon?
cell density
How does quorum sensing work?
Auto-induction 1 or 2 leads to increased concentration as cell density increases. Once signaling compounds reach a threshold level, gene expression is activated.
T/F. Expression of genes for antibiotic resistance at high cell densities may provide protection.
True.
T/F. Quorum sensing does not have the potential to influence community structure by encouraging the growth or beneficial species and discouraging the growth of competitors.
False, Quorum sensing DOES have the potential to influence community structure by encouraging the growth or beneficial species and discouraging the growth of competitors.
T/F. Commensal species produce and respond to high levels of autoinducer - 2, while pathogens produce and respond to low levels of these substances.
False, Commensal species produce and respond to LOW levels of autoinducer - 2, while pathogens produce and respond to HIGH levels of these substances.
Therefore, AI-2 may determine the switch between commensal to pathogenic communities.
Biofilm bacteria are ___-___ times more resistant than planktonic bacteria to antibiotics.
1000-1500
Why is it a good mechanism of antibiotic resistance that biofilm bacteria grow more slowly?
- Antibiotics depend on cell turnover for efficacy
- Slow-growers express ‘non-specific defense mechanisms’
- Slow growers make more exo-polymers
How do exo-polymers retard diffusion?
- Ion-exchange mechanism prevents highly charged molecules from reaching deeper zones
- Extracellular enzymes (beta-lactamases, formaldehyde dehydrogenase, formaldehyde lyase) inactivate antibiotics
Biofilm bacteria are able to evade antibiotics because they express different genes due to gene ___ and ___ expression of biofilm existence.
transfer; phyenotypic
T/F. Classically, a pathogen is not normally present and produces virulence factors that damage the host directly (toxins) or induce host to damage itself (immune responses).
True.
Why is it that presumed oral pathogens don’t quite fit the model of a classical pathogen?
- normally present throughout life
2. damage requires presence in large numbers
Explain the ecological concept of oral microbial diseases.
- Ecological shifts lead to changes in proportions
- Balance shifts in favor of “pathogens”/disease
- Periodontal disease is an example of ‘ecological catastrophe’
Why is the structure of biofilms clinically significant?
Changed tooth-brushing paradigms
Hard to reach interproximal and fissures
Non-contact brushing can remove towers and mushrooms by shear forces
Antibiotic sensitivity testing distinguishes between ___ and ___ bacteria.
planktonic; biofilm
What are some targets for biofilm therapy?
AI-2
vaccines that target common resistance genes
The periodontal ___ can translocate pathogens from pockets to health sites.
probe
T/F. Drug-resistant strains can translocate to neighboring teeth, teeth can act as reservoirs for colonization of implants., and bacteria can infect membranes in GTR.
True.
What is the rationale for one-stage, full-mouth disinfection by Leuven?
Full-mouth scaling and root-planing within 24 hrs.
Subgingival irrigation with 1% chlorhexedine
Tongue brushing
Oral antimicrobial rinse
Plaque can form on ___ abutments. Those that fail have a microbial composition similar to ___ disease.
implant; periodontal
