week 5 Flashcards
What colour is gram positive and why?
Purple because there is lots of peptidoglycan in the cell wall
What is an example of a gram positive bacteria?
Lipotechnoic acid
What colour is gram negative and why?
Pink, thin layer of peptidoglycan
What is an example of gram negative?
Lipopolysaccharide
What is saccharolytic metabolism?
resides in supragingivial plaque and sugars promote acid production.
What does it mean that saccharolytic metabolism forms fructans
its food storage for biofilm bacteria and it aids in bacterial attachment.
What is Asaccharolytic metabolism?
breaks down proteins into amino acids and nitrogen in periodontal pockets
What are obligate anaerobes?
O2 is toxic because they lack the enzymes to break it down. Eg P Gingivalis
What are facultative anaerobes
grow in or without oxygen, supragingival species such as streptococcus mutans
what are microaerophilic bacterias?
require little O2 for growth
Capnophilic bacteria
requires CO2
Is the development of the oral biofilm in toddlers influenced by the eruption of teeth?
Yes
At what age does the oral microbiome become complex?
3 yrs
Does the oral microbiome continue to develop in complexity over time?
Yes
Is an edentulous patient’s oral microbiome as complex as that of a fully dentate adult?
No
List three main components of the oral microbiome:
Shedding surfaces, non-shedding surfaces, secretions
Can plaque biofilms form on shedding surfaces?
Yes
Are shedding surfaces self-cleansing?
Yes
What are aerobic shedding surfaces?
gum tissues, soft and hard palate
What are anaerobic shedding surfaces?
Interproximal areas, subgingival areas, back of tongue
Give 4 examples of non-shedding surfaces in the oral cavity
Hard surfaces such as restorations, dentures, ortho, implants, and teeth. supra and subgingival
What is the source of saliva?
salivary glands
What is the source of gingival crevicular fluid (GCF)
blood plasma
What is the habitat provision for saliva and GCF?
Moist, aqueous, nutrient-rich environment beneficial for biofilms. Flushing action eliminates planktonic bacteria and poorly adhered cells
What are the nutrients in saliva?
Water, carbs, protein, vitamin
What are the nutrients in GCF
protein, Haem containing nutrients, erythrocytes
What are the antibacterial properties of saliva?
flushing action, antibodies, mucins, agglutinins
What are the antibacterial properties of GCF
Cytokines, antibodies, Compliment neutrophils
What are the habitat and growth requirements of bacteria
oxygen, pH, temp, nutrients, food webs, carb metabolism, protein metabolism
What is the normal pH of the gingival sulcus in health?
6.75-7.25
what change in pH occurs in gingival plaque during periodontal disease?
increase
What effect does an increase in pH in gingival sulcus have on the growth of periodontal pathogens?
improves it
what is the normal temp of gingival sulcus in health?
36.8 degrees
What change in temperature occurs in active periodontal pockets?
increase
What effect does an increase in temp have on enzyme activity and gene expression (eg protease production by P. gingivalis
increase
Why are bacterial adhesion to the pellicle and coaggregation important bacterial interactions in biofilms?
oral bacteria can get washed away quickly by saliva
What cell surface features facilitate surface binding by early colonising bacteria?
pili, flagella, receptors
What is a foodweb?
interdependent relationships between different bacteria occur when the metabolic byproducts of one bacteria can be used for another species
Give an example of a food web
streptococci produce bacteria which is used by veillonella spp
List the three innate host defenses present in the periodontal tissues.
saliva - lubricates, digests, nutrition, antibodies
Junctional and Sulcular Epithelial Barriers - attachment to tooth, antimicrobial defense, GCF flow
Does the junctional epithelium have an active role in host defense
yes
List the elements of the non-specific plaque hypothesis
all plaque is equally pathogenic, it is the bulk that causes the disease
what is the supporting evidence for the NSPT
plaque growth resulted in gingival inflammation within 10-20 days, after reinstituting oral hygiene it resolved back to health
What were the deficiencies or limitations of the NSPT?
not all patients progressed from gingivitis to periodontitis
of those patients with gingivitis who progressed to periodontitis, what happened
there was a spectrum of disease progression, some patients had rapid attachment loss with little plaque, not all sites within the patient behaved the same way
During the 1950’s and 1960’s, the progression of periodontitis was thought to be slow, linear and continuous.
Given contemporary knowledge, are the linear pathogenesis and continuous disease progression models valid?
No
The advent of which two microbiological techniques greatly expanded our knowledge of periodontal
microbiology?
postulates for “putative periodontopathogens” and DNA-DNA hybridisation
in health, there is little
bacterial load, and saccharolytic plaque.
In health, there is predominantly
aerobic gram positive organisms
In health, the species are
cocci
In gingivitis the species are
gram positive rods
In periodontitis there is high
bacterial load and subgingival plaque, asaccharolytic bacteria, motile rods
In periodontitis the species are
gram negative rods
What is the Specific Plaque Theory?
A few specific pathogens within the biofilm that causes periodontisis. The remaining microbiome doesn’t influence the disease process
If the SPT explained the aetiology of periodontitis, how does this knowledge shift the approach to periodontal
treatment?
continued use of antibiotics resulted in antibiotic resistance and sensitivity. putative periodontopathogens returned after sessation of antibiotic use
The aetiology of which two periodontal conditions are explained by the SPT? List the applicable bacteria.
periodontitis - opportunistic endogenous bacteria
gingivitis - treporema denticola and fusiforms
List the main limitations of the SPT.
disease is caused by resident microflora, the bacteria associated with active periodontitis are found in low proportions of the dental plaque in health and gingivitis states
List four significant contributions Haffajee and Socransky made to periodontal microbiology.
identified purative periodontal pathogen
used DNA to study complex microbial ecosystems
associated red complex bacteria with periodontal disease parameters such as probing depth
List the five postulates or conditions a bacterium must achieve before being described as a “putative
periodontopathogen”
association, elimination, host response, animal studies, virulence factors
describe “association” as a requirement for something being putative periodontopathogen
in higher numbers in disease
describe “elimination” as a requirement for something being putative periodontopathogen
reduced numbers in health
describe “Host Response” as a requirement for something being putative periodontopathogen
higher antibody levels against the putative periodontal pathogen in periodontitis patients
describe “animal studies” as a requirement for something being putative periodontopathogen
the putative pathogen isolated from periodontal pockets must cause periodontitis in animals
describe “virulence factors” as a requirement for something being putative periodontopathogen
the putative pathogen must demonstrate virulence factors that cause periodontal disease
Name the three bacteria that make up the red complex
P gingivalis, T forsythia, T Denticola
What is the cell morphology of P gingivalis, T Forsythia, T Denticola
Red Complex
What are the characteristics of P Gingivalis
non-motile, gram-negative, requires haemin for growth
What are the characteristics of T Forsythia
gram negative, difficult to culture, grows on blood agarplate
what are the characteristics of T Denticola
gram negative, difficult to culture only possible through DNA analysis
what are the virulence factors of P Gingivalis
Trypsin-like proteases, gingipains, invade epithelial cells
What are the virulence factors of T Forsythia
trypsin like proteases, invades epithelial cells
What are the virulence factors for T Denticola
adherence, motility, trypsin, invades epithelial cells
Summarise the conclusions from Socransky, Haffajee, Goodson, Lindhe’s (1984) Random burst theory paper.
Sites enter a state of disease activity for short periods of time followed by longer periods of remission and no activity
Does periodontitis progress on a site-level or at a patient (or dentition) level?
site level
What is a biofilm?
an arranged community of microorganisms that are 3-D, located in an aqueous environment, embedded in a protective slime/sticky matrix called extracellular polymeric substance
Are conditions the same throughout a biofilm?
no
Are conditions the same throughout a biofilm?
no
Does this property of biofilms increase or decrease the biodiversity of plaque?
increase
What is “extracellular polymeric substance” (EPS)?
consists or organic and inorganic material derived from bacteria, saliva, and GCF
List three main functions of EPS.
- helps bacteria stay together
- protects against phagocytosis
- provides a source of energy and nutrients to bacteria
What is the purpose of “fluid channels” in a biofilm”?
allows movement of nutrients and O2 for bacteria and removes waste products and enzymes. communicates with other genetic materials and increases metabolic diversity.
what are the main stages of biofilm formation
- formation of pellicle
- passive transport of salivary microorganisms
- reversible attachment of bacteria to pellicle
- irreversible attachment of early colonisers
- secondary colonisers bind, maturation, detachment
describe pellicle formation
adsorption of salivary proteins onto a tooth surface. electrostatic attachment with hydroxyapatite onto enamel
describe irreversible attachment of early colonisers
adhesins to pellicle receptors (streptococci) attach to glycoproteins by their fimbriae/pilli
describe secondary colonisers bind
co-aggregation - receptor binding driven by bacterial cells, aerobic bacyeria consume oxygen, inflammation
describe maturation of biofilm formation
stable, mature plaque, diverse ecology, motiles covered by EPS
what is the purpose of detachment in biofilm formation?
allows colonization elsewhere
which bacteria are early colonising species?
blue, purple, green, yellow
which bacteria are orange
secondary colonisers
which bacteria are red
late/tertiary colonisers
Does saliva influence the binding of the biofilm layers and constituents?
yes
Do biofilms protect resident bacteria from antimicrobial agents?
yes
Can biofilms become resistant to antimicrobials through horizontal gene transfer?
yes
Give two examples of bacterial communication throughout a biofilm.
when an antibody dies, they lyse and eDNA is released and easily transferred to another bacterium. Horizontal gene transfer, free uptake of DNA
Can bacteria actively suppress neighbouring species?
yes
where does supragingival plaque form?
interproximal surfaces, enamel pits and fissures
where does subgingival plaque form?
epithelium, tooth and root surfaces in a periodontal pocket
what are the oxygen conditions of supragingival plaque
aerobic and anaerobic
what are the oxygen conditions of subgingival plaque?
anaerobic
what is the nutrient source for supragingival plaque?
Saliva
what is the nutrient source for subgingival plaque?
GFC
what are the typical bacteria properties of supragingival plaque
sacchorolytic gram positive
what are the typical bacterial properties of subgingival plaque
motile, gram negative
what is an example of a supragingival bacteria
streptococcus mutans
what is an example of a subgingival bacteria
spirochaetes
How does calculus form?
by mineralising plaque, precipitation of phosphate salts within
what are the differences in colour between supra and subgingival plaque?
sub is darker because it is stained with haemin from blood
Bacteria are required to trigger and propagate the host response in periodontitis. True or False
True
Is the host response responsible for most of the tissue damage in periodontitis?
Yes
What innate host defenses are present in the periodontium?
Resident flora, secretions, epithelial barriers, inflammation, compliment proteins
What triggers gingival inflammation?
plaque bacteria and plaque antigens
What is the speed of inflammatory response to plaque bacteria?
rapid
What is the speed of immune response to plaque antigens?
slow
what is involved in inflammatory response to plaque bacteria?
epithelial barrier, compliment cascade, cytokines, adhesion molecules
what is involved in immune response to plaque antigens?
Helper Ts, cytotoxics, B cells, antibodies, macrophages, compliment cascade
which response to plaque bacteria triggers chronic inflammation?
immune response
what happens when inflammatory response and immune response happen together?
chronic stimulation because plaque is not removed by host responses
Why are neutrophils the “first line of defense” against the plaque front?
phagocytose foreign bacteria, create extracellular nets, degranulate lysosomal enzymes
How do activated cytotoxic T cells cause tissue damage in periodontitis?
compliment system forming membrane attack complex, stimulates B cells, creates pores that disrupts bacterial cell wall integrity and cell lysis occurs.
How does antibody release by plasma cells cause tissue destruction in
periodontitis?
targets soluble antigens in extracellular material leading to tissue destruction
What is bystander damage?
host destruction of its own tissue. Involves alveolar reabsorption, connective tissue breakdown and apoptosis of epithelial cells
How does periodontal tissue destruction of collagen occur?
14-21 days of plaque formation, anoxia in capillaries causing RBC to escape breaking down collagen
How does periodontal tissue destruction of bone occur?
extensive number of T cells and plasma cells
For “Initial lesion” of biofilm induced gingivitis how many days has the plaque been there and what it is the state of the gingiva?
2-4 days, healthy
For “Early Lesion” of biofilm induced gingivitis how many days has the plaque been there and what it is the state of the gingiva and what immune cell type is working?
1 week, supragingival plaque, gram positive microbes, some destroyed collagen fibres, T cells and macrophages activated
For “Established Lesion”/chronic of biofilm induced gingivitis how many days has the plaque been there and what it is the state of the gingiva and what immune cell type is working?
1-2 weeks, pocket formation, chronic gingivitis, damaged fibroblasts and collagen fibres, plasma cells derived from B
For “Advanced Lesion” of biofilm induced gingivitis how many days has the plaque been there and what it is the state of the gingiva and what immune cell type is working?
over 2 weeks, periodontitis, coronal detachment, damaged fibroblasts collagen fibres and alveolar bone reabsorption, plasma cells
Do all established lesions progress to advanced lesions?
No
The red complex bacteria are implicated in periodontal tissue breakdown,
however the host response to these bacteria (i.e. inflammation and immune
responses) is responsible for how much of the tissue destruction in
periodontitis?
80%
what are the main concepts of symbiosis
a mutual relationship of oral flora and host. nutrient competition, barrier function, protection
what are the main concepts of dysbiosis
the shift from gram positive to gram negative, altered pH or diet, smoking causing a pathogen enriched microflora
summarize ecological plaque theory
both the quantity and quality of bacteria can trigger the dease condition and the host risk factors contribute to the severity and extent of the resulting gingivitis and periodontitis
summarize keystone pathogen theory
host defenses can’t effectively clear the pathogen
summarize the IMPEDE Model
no RX - dysbiosis and tissue damage can be exacerbated
