Microbiology for Dentists Theme 2 Flashcards
What is the autochthonous microbiotia ?
microorgansims characteristically found at a particular site
What is the allochthonous microbiotia ?
microorganims transiently present at a site
they dont thrive at the site but may colonise transiently if the site becomes compromised.
Where are archaea detected at increased levels ?
periodontal disease
What are the most common type of virus found in the mouth ?
bacteriophages
What is the most common viral pathogen in the mouth ?
HSV-1
Which viruses are asymptomatic in the mouth so care is needed for cross infection ?
hepatitis B and HIV
What is the most common fungus in the mouth ?
candida
What are the most abundant bacteria in the mouth ?
oral streptococci
What are the characteristics of oral streptococci ?
gram positive
alpha haemolytic
Which diseases are bacteria responsible for ?
caries
periodontitis
abcesses
What happens with oral streptococci and kiss plates ?
oral streptococci are alpha haemolytic - brownish colour change
What is alpha haemolysis ?
produces hydrogen peroxide which bleaches haemoglobin - Fe changes transition states from Fe3+ to Fe2+
How many species of bacteria naturally colonise the mouth ?
700 species- 13 phyla
How many of the species in the mouth can be cultured ?
50%
How long does it take to form mature dental plaque ?
1-4 minutes
Where do bacteria live in the mouth ?
tongue
cheek
palate
teeth
What are the lips, cheeks and palate like as a microbial habitat ?
have epithelial cells that are shed continually which get rid of bacteria
What is the tongue like as a microbial habitat ?
highly papillated which creates an anaeorbic environment
tongue is reservoir for obligate anaerobes
What are the teeth like as a microbial habitat ?
no shedding as no epithelial cell
prone to colonisation by bacteria
What is the enamel pellicle ?
a protein film between enamel and bacteria that supports and inhibits bacterial adhesion. Prevents enamel dissolution
Why do we culture microflora ?
understand physiology and biochemistry
link organism to disease
identify pathogenesis mechanisms
test antibiotics
How can it be hard to culture certain microflora ?
some bacteria are dormant - not easily reactivated
some species are fastidious
What are the culture independent methods of microbial analysis ?
PCR
Hybridisation
NGS- Metagenomics/targeted
What are holobionts ?
we are superorganisms of our on cells and microbiotia - act as one biological unit
Which streptococci are enriched in dental plaque compared to soft tissues ?
gordonii and sanguinis
Is saliva sterile ?
it is only sterile when secreted but accumulates with bacterial cells
Are there more bacteria attached to epithelial cells than there are free in saliva ?
more attached to epithelial cells
How are bacteria removed from oral surfaces ?
sloughing epithelial cell
mechanical debridement
active release
What is the problem with sampling saliva to look at the oral microbiome ?
there are different amounts of bacteria in the plaque compared to the soft tissue
What is the core microbiome ?
13 phyla present in almost everyone
What is the peripheral microbiome ?
species present in some and not others
Why do some microbiomes form clusters in different individuals ?
differences in the metabolome
this could be correlated with disease susceptibility
What does the acquired enamel pellicle do ?
it protects enamel
protects against the dissolution of enamel by keeping calcium and phosphate together
How does saliva help control plaque accumulation ?
aggregating bacteria which are then swallowed
having antimicrobial effects
Which salivary proteins bind to bacteria ?
MG2
Gp340
PRPs
Statherin
What are the roles of the salivary proteins ?
agglutinate
aggregate
inhibit
promote/inhibit microbial colonisation
What is aggregation/agglutination ?
occurs in the fluid phase
results in large clumps
large clumps removed in swallowing
What is adhesion ?
proteins in the saliva pellicle interact with bacteria resulting in the adhesion of bacteria to teeth
What is unique about salivary proteins ?
exhibit different bacteria binding proteins when in solution than on the surface
What are immunoglobulins present in saliva as ?
secretory IgA
What is the resting flow rate of IgA ?
33 mg/100 mL
What is the stimulated flow rate of IgA ?
6 mg/100 mL
What is the purpose of antibodies ?
to agglutinate bacteria - removed by swallowing
Which immunoglobulins are present in the GCF and what is their purpose ?
IgG and IgM
activate complement and opsinisation
What are examples of host receptors that bind bacteria ?
PRPs
Stahtherin
What are Proline rich proteins (PRPs) ?
they act in calcium phosphate stabilisation
found in high concentrations in parotid and submandibular saliva
Why are PRPs cyptitopes ?
they change conformation and reveal binding sites that bacteria want to bind to
What are the fucntional domains of PRPs and what do they do ?
N term- binds to Hydroxyapatite
C term binds to Actinomyces, Strep mutans and Sanguinis
What is statherin ?
main funcntion is calcium phosphate stabilisation
binds to hydroxyapatite and bacteria like actinomyces
secreted by parotid and submandibular glands
What does lysozyme do ?
cleaves bacterial cell walls
causes no enzymatic cell degradation
Where can you find lysozyme ?
tears
saliva
sweat
What is the downside of lysozyme ?
not equally effective against all bacteria
oral bacteria are more tolerant of it
What does lactoperoxidase do ?
catalyses the production of hypothiocynate from hydrogen peroxide ( by product of bacterial metabolism) and thiocyanate (in saliva)
What does hypothiocyanate do ?
uncharged so penetrates bacterial cell membranes
inhibits bacterial glycolysis
What does lactoferrin do ?
binds iron and makes it unavailable
What is the acquired enamel pellicle ?
protein film that forms on the surface of enamel
contains salivary glycoproteins and bacterial products
eg. PRPs which allow bacterial adhesion
Which tooth surfaces are available for colonisation ?
fissures
smooth surfaces
approximal
gingival crevice
Is supragingival plaque aerobic or anaerobic ?
aerobix
Where is supragingival plaque present ?
in health on the teeth
in cracks and fissures it can leads to caries
What is the nutrient source of supragingival plaque ?
saliva
Is subginigival plaque aerobic or anaerobic ?
anaerobic
What are significant amounts of subgingival plaque associated with ?
periodontitis
ginigivitis
What is the nutrient source of subgingival plaque ?
gingival crevicular fluid
When does plaque accumulate faster ?
day
Where do pioneer colonisers attach to ?
salivary pellicle
What are environmental factors affecting plaque formation ?
diet
smoking
What are bacterial factors affecting plaque formation ?
co aggregation
bacterial adhesins that recognise the pellicle
What is the cyclic nature of plaque build up ?
initial colonisation- Streptococcus, Actinomyces, Veillonella
Microflora alteration phase- Fusobacterium and Prevotella
Lack of cleaning leads to dental caries and periodontitis
What is the role of the acquired enamel pellicle ?
primary colonising bacteria in plaque attach to it
What are the characteristics of the acquired enamel pellicle ?
1-3 micrometres thick can permeate the outer layer of enamel not easily removed present on most enamel surfaces a deposit of saliva proteins
How is the enamel pellicle formed ?
by the preceipitation of denatured saliva proteins
it is selective- proteins with a high binding affinity bind to the tooth surface
As well as saliva proteins what else does the pellicle contain ?
components of the GCF
oral mucosa and microbial cells
What are the functions of the enamel pellicle ?
lubricant
reduces mobility of calcium and phosphate ions - this stops the dissolution of enamel - demineralisation
prevents inappropriate crystal growth- stops dental calculus
contains enzymes
What is within the pellicle which prevents inappropriate crystal growth ?
statherin and PRPs
Which active enzymes are within the pellicle ?
amylase lysozyme peroxidase carbonic anhydrase glucosyltransferase
What does the pellicle do with bacteria ?
can inhibit and be a substrate for bacterial adhesion
What is within the pellicle that allows bacteria to adherer ?
the salivary proteins have receptors for bacteria
Name some salivary proteins in the pellicle ?
MGI Amylase PRPs Statherin Gp340
Which bacteria are present in initial plaque ?
50% of bacteria in initial plaque are streptococci
What are the human oral streptococci groups ?
mitis
anginosis
salivarius
mutans
What is the mitis streptococcus group ?
the most numerous in the mouth
What is the anginosis streptococcus group ?
commensal but found at abcesses
What is the salivarius streptococcus group ?
generally commensal but also used as probiotics
also found elevated in dental caries
What is the mutans streptococcus group ?
associated with dental caries
found in mature plaque and is not an early coloniser
What is the most abundant bacterium in initial plaque ?
Streptococcus Oralis
What are streptococcal adhesins ?
they are proteins on the surface of oral streptococci that can adhere to receptors on salivary proteins in the pellicle
What is an example of a streptococcal adhesin ?
antigen I/II
What is antigen I/II ?
a large multi domain protein on the surface of oral streptococci
mediates adhesion to the gp340 salivary agglutinin protein in the pellicle
What are the other functions of antigen I/II ?
can bind to to other bacteria like actinomyces
What structural properties allow antigen I/II to bind to other bacteria ?
it has a C-motif that covalently binds to peptidoglycan
What are the pioneer coloniser species ?
actinomyces
veillonella
What are actinomyces ?
gram positive pleimorphic rods
facultative anerobes
harmless but can cause disease
What are veilonella ?
gram negative cocci
strict anaerobes
feed on lactate produced by other oral bacteria
Does veilonella cause disease ?
not associated with disease but elevated in caries
found in supraginigival plaque although its aerobic
How does veilonella survive in supragingival plaque if its anaerobic ?
the surrounding aerobic bacteria use the oxygen so that the environment becomes anaerobic
What is the process of dental plaque formation ?
adhesion to the surface coaggregation coadhesion mature biofilm with matrix dispersal
What is the appearance of mature supragingival plaque ?
stratified
gram positive cocci and short rods a tooth surface with filament towards the outer layers
What does supragingival mature plaque cause ?
causes a shift towards acidogenic/aciduric bacteria
Does the amount of plaque correlate with dental caries ?
no evidence to support correlation
What does accumulation of plaque at the gum line cause ?
irritates tissues and can lead to calculus formation
this leads to gingivitis (reversible)
can progress to periodontitis (irreversible)
accompanied with a change in oral microbiotia
What is present in the subgingival crevice in the mouth ?
few bacteria
anaerobic bacteria- not found elsewhere
asacchrolytic, proteolytic bacteria found here
What do early colonisers support the attachment of ?
bridging organsims
What are bridging organisms ?
they stick to perio pathogens and trigger inflammation of the gingiva
What is an example of a bridging organism ?
fusobacterium nucleatum
What is fusobacterium nucleatum ?
gram negative
proteolytic
anaerobic
long rods
What does fusobacterium nucleatum do ?
forms co aggregates with early coloniseres and later colonisers
invades host epithelial cells
present in high numbers in subgingival plaque
What is supragingival calculus a deposit of ?
saliva
What is subgingival calculus a deposit of ?
serum
What does the rough surface of calculus do ?
trigger inflammation
leading to gingivitis and periodontitis
Where does calculus form ?
near salivary duct opening
What is calculus ?
mineralised plaque
What are sialoliths ?
form in salivary ducts
they are supersaturated Calcium phosphate
What are the mechanisms of enamel loss ?
fracture
caries
erosion
abrasion
What is caries ?
loss of enamel due to bacterial acid production
What is erosion ?
loss of enamel due to dietary acids
What is abrasion ?
loss of enamel due to mechanical wear
What is the main component of enamel ?
biological appatite
What is biological appatite made from ?
Ca
Phosphate
hydroxyl ions
Is biological appatite soluble ?
sparingly soluble
increased solubility at low pH
What happens to pH after a sugar rinse according to stephans curve ?
there is a drop in pH
What happens after the drop in pH ?
after the decrease in pH the pH tries to return to normal
this is the time in which the enamel dissolved as it is exposed to a low pH
What is the critical pH ?
roughly 5.5
this is the pH which under the enamel dissolves quicker
What happens if you rip water on enamel ?
enamel will eventually dissolve
an equilibrium isnt reached as water is always being replaced
fresh water doesnt have any calcium in it - calcium always leaving the tooth
Why doesnt saliva dissolve enamel ?
supersaturated calcium phosphate doesnt come into contact with the enamel as the statherin and PRPs bind to the ions maintaining the enamel
How do you calculate the solubility product ?
the ion concentrations multiplied
the ion concentrations must be multiplied by their respective power
What is the ionic product ?
the same as the solubility product but in solution
If IP>SP ?
solution is supersaturated
unless the ions are stabilised in some way like by stahterin etc
What if SP >IP ?
solution is unsaturated and you get dissolution
What are the 2 ways that calcium hydroxyapatite can dissolve ?
loss of hydroxide ions
loss of phosphate ions
What happens with the loss of hydroxide ions ?
adding acid means hydroxyapatite dissolves phosphate and hydroxyl ions
increasing acid means hydroxyl ions must decrease - pulling out hydroxyl ions to maintain equilibrium
What happens with the loss of phosphate ions ?
hydrogen ions bind to phosphate ions - pulling out phosphate ions
IP drops and SP is higher - dissolution
What is the effect on the critical pH if someone has lower calcium and phosphate concentrations ?
leads to a higher critical pH of about 6.5- this means there is a greater range of pH over which dissolution can occur
The KSP of a sparingly soluble halids is 4x10^8 moles
How many moles of each element will dissolve in a litre of water ?
square root
solubility product is the product of the ion concentrations.
2x10^4
in the global burden of diseases which is the most 2nd prevalent disease ?
Latent tuberculosis
What is the name for the total genetic information in a complex population ?
metagenome
Which of the following species is most strongly acidogenic ?
lactobacillus fermentum
The concept that the total amount of plaque is responsible for dental caries is ?
specific plaque hypothesis
Which of the following species belongs to the mutans group streptococci ?
Streptococcus Sobrinus
At the crtical pH of enamel what is the relationship of the KP to IP ?
KP=IP
In acidic conditions hydroxyapatite dissolves because ions are removed from solution. Which ions are likely to be removed ?
Hydroxide
phosphate
What are the different types of caries ?
primary secondary residual active v inactive early childhood caries
What is early childhood caries ?
presence of one or more decayed missing or filled tooth surfaces in any primary tooth between birth and 71 months
Which type of caries are becoming prominent ?
occlusal, interproximal and EDJ caries ever since the late 19th century
Why is caries set to increase in global prevalence ?
greater longevity and population growth
Which bacteria are commonly acossiated with caries ?
mutans streptococci
lactobacillus
actinomyces
bifidobacterium - scardovia wigiassae
How are the streptococci broken up ?
broken into groups with each group containing differnt species
What bacteria does the mutans group contain ?
strep mutans
strep sobrinus
What are the features of the mutans streptococci ?
gram positive
catalase negative
sacchrolytic
facultative anaerobes
What are the caries associated with streptococci ?
S mutans
S sobrinus
non mutans acossaited low pH streptococci
What are the characteristics of S mutans ?
acidogenic
aciduric
produces glucans from sucrose
What is different about S.Sobrinus comapred to S.mutans ?
more acidogenic
more adherent
Why does Kochs postulates not match up with Strep mutans ?
organism must be present in all cases of disease and not in healthy individuals- this cannot be the case because strep mutans is in 96% of the population and the level rather than the presence is important
Which bacteria are acossiated with early childhood caries ?
bifidobacterium
scardovia wiggisae
they have been isolated on acid agar
What are the characteristics of Scardovia Wiggisiae ?
anaerobic
pleomorphic
gram positive bacilli
sacchrolytic - produces acetic and lactic acid
What is the problem with S mutans ?
it has a low predictive value- there are other species like Prevotella that have a higher predictive value
What are germfree animals ?
no microorganism present in them
used to investigate microbial aetiology
What are examples of virulence factors ?
adhesins
acid production
aciduricity
What are examples of adhesins ?
antigen I/II
glucosyltransferases
aciduricity
How do bacteria remain aciduric ?
DNA repair proteins
protective membrane proteins
How are carbohydrates utilised by bacteria ?
glucose and sucrose make acid and intracellular storage polymers
sucrose also makes exopolysaccharides
How do bacteria uptake sugar ?
polysaccharides are digested
monosaccharides and disaccharides are imported
What is xylitol ?
a sugar substitute
imported, metabolised and knocked out - futile cycle
How is glucose uptake described ?
constitutive
What happens in high sugar conditions ?
lactate is the major product
homolactic fermentation
intracellular polysaccharides are made
What happens in low sugar conditions ?
mixed acid fermentation - heterofermentation
lactate dehydrogenase is inhivited
Intracellular polysacchrides are digested
Why is oxygen important in fermentation ?
it is an important regulator
What are intracellular polysaccharides ?
produced via glucose 1 phosphate when carbohydrates are in excess
make a glycogen type glucan
they are broken down and used for glycolysis in starvation
How do you get greater acid tolerance ?
pre acidification results in greater acid tolerance
What are mechanisms of acid adaptation ?
reduced permeability of cell membrane to protons
induction of proton translocating ATPase
induction of alkali production systems
induction of stress proteins
What are the purpose of stress proteins ?
protect enzymes and nucleic acids from denaturation
What alkali systems are higher in caries free subjects ?
salivary arginine deaminase
urease
What do strep gordonii and strep sanguinis do with urease ?
arginine breaks down to urea by arginase
urea broken down to carbon dioxide and ammonia bu urease
What do strep salivarius and actinomyces do with arginine deaminase ?
arginine broken down citrulline releasing ammonia
citrulline enters the carbomoyl phosphate cycle releeasing ammonia
What are the macromolecules that form the basic structure of the matrix ?
polysaccharides
proteins
nucleic acids
What do the macromolecules do ?
form a scaffolding
What are the small molecules that are trapped in the matrix ?
nutrients
signalling molecules
trace metals
What are exopolysaccharides ?
polymers made of sugar residues that are secreted by a microorganism into the environement
What are the 2 types of exopolysaccharides ?
glucans and fructans
What are glucans made by ?
glucosyltransferase
What are fructans made by ?
fructosyltransferases
What are glucans ?
polymer of glucose formed outside the cell using sucrose as the substrate
Why is sucrose the substrate for glucan synthesis ?
contains a high energy glycosidic bond
What are 2 examples of fructan polymers ?
inulins and levans
What are inulins ?
insoluble
contain beta 2,1 bonds
can be cross linked with beta 2,6 bonds
identical to a fructose polymer in vegetables- used as a long term carbohydrate storage rather than starch
Who synthesises inulins ?
streptococcus mutans
steptoccus salivarius
What are levans ?
contain beta 2,6 bonds
water soluble
rotate polarised light to the left
Who makes levans ?
strep sanguinis
strep salivarius
strep sobrinus
What are the 2 examples of glucan polymers ?
mutans and dextrans
What is mutan ?
water insoluble
core is alpha 1-3 linked
70% of plaque exopolysaccharide is mutan
some can be mostly alpha 1-3 linked but with some alpah 1-6 links
What is dextran ?
soluble almost all alpha 1-6 bonds rotates polarised light to the right synthesised by strep salivarius many variations with alpha 1-3 linked glucose side chains
How do enzymes form glucans and fructans ?
enzymes make alpha 1,3 and alpha 1.6 links
What is special about enzymes that make glucans and fructans ?
they dont need a primer
can add to preexisting glucan which induces a conformational change
How are GTFs made and secreted ?
they are secreted into plaque and are extracellular
different bacteria secrete different enzymes
What do glucans act as ?
receptros for unrelated GTFs
What are the other enzymes present in the matrix ?
proteases
dextrinases
What are some examples of GTFs ?
glucansucrase
dextransucrase
mutansucrase
What are some examples of FTFs?
fructansucrase
inuslosucrase
levansucrase
What does GTF-S cleave ?
water soluble dextran like glucans with an alpha 1-6 backbone
What does GTF-I cleave ?
insoluble glucans with alpha 1-3 backbone
What does GTF-SI cleave ?
partially soluble alpha 1-3 polymer
Which gene codes for GTF-I ?
gtfB
Which gene codes for GTF-SI ?
gtfC
Which gene codes for GTF-S ?
gtfD
How many types of FTFs are there ?
2- one synthesis an inulin like polymer and the other a levan
Which bacteria make fructans ?
strep mutans
strep salivarius
What is mutan essential for ?
strep mutans biofilms
Which sugar produces a thicker biofilm matrix ?
bacteria grown in glucose produce a thicker matrix and bacteria grown in sucrose thicker matrix
What can mutanase potentially do ?
treatment with mutanase can potentially reduce biofilm formation
What will knocking out genes like gtfB do ?
reduce biofilm formation - thin biofilms
What do biofilms do with microcolonies ?
biofilms form mutan rich colonies- clusters of polysaccharides that have a low pH - acid is localised to certain areas- enamel degradation
What happens if you add sucrose to a culture of bacterial cells ?
the bacterial cells will clump as they will use sucrose to make glucans
bacteria have glucan binding proteins on the surface
aggregate
How are FTFs related to caries aetiology ?
FTFs are very active in plaque
however the amount of fructan in plaque is low
suggests that fructan is turned over rapidly and then used quickly as a short term energy store
How are FTFs thought to contribute to caries ?
they extend the fermentation time on plaque bacteria
What do glucans do with mutans streptococci ?
they help them to stick
What do soluble dextrans mediate ?
cell aggregation
What do insoluble glucans contribute to ?
cell adherence
How do other bacteria adhere to strep mutans ?
via glucan ridges
Which interactions do glucan bridges lead to ?
metabolite cycling
signalling
competition
What are amyloids ?
proteins that form robust fibrils that are hard to degrade
they run perpendicular to the length of the fibril
What are fucntional amyloids ?
have a function in biofilm stabiliisation
melanin formation
innate antiviral immune response
Which bacteria produce large amiunts of the extracellualr DNA ?
p.Aureginosa
What does treatment with DNase lead to ?
disrupts biofilms temporarily
can reduce periodontal pathogen colonisation
What re the functions of extracellular DNA ?
gene transfer chelates metal ions biofilm formation antimicrobial protection nutrient uptake biofilm stability
What is plaque fluid ?
the fluid which fills spaces between bacteria in dental plaque
How much is the plaque fluid ?
30% of total plaque volume
What is the composition of plaque fluid ?
modified saliva
bacterial metabolites
gingival fluid
What is the function of the plaque fluid ?
acts as a buffer between saliva and tooth
maintains calcium, phosphate ans fluoride concentrations
can retain antimicrobials in tooth wash
What is periodontitis ?
spectrum of diseases
affects tooth supporting structures
What happens to the junctional epithelium in periodontitis ?
junctional epithelium at base of gingival crevice migrates down root of tooth to form periodontal pocket
Migration of the junctional epithelium is a result of ?
direct microbial action but also a result of exaggerated host immune response
Changes in the microbiotia lead to ?
changes in the environmental conditions
What is the size of deep pockets ?
5mm +
What can recession be to the extent of ?
apical third of the tooth
What are some manifestations of periodontitis ?
loss of periodontal bone support
mobility
tooth loss
triangular shaped boe defects- intrabony periodontal pocket
What are some factors influencing periodontal disease ?
tobacco oral hygeine medication type 2 diabetes stress systemic
What is the development of periodontal disease ?
initial microbial homeostasis
change in environment leads to altered microbial population
exaggerated inflammatory response
damage to periodontium
What is the cementum colonised by ?
gram positive species like actinomyces and streps- early colonisers
bridging organisms- fusobactrium nucleatum allow microbial organisms to attach
environmental change can lead to co-aggregation and co-adhesion
What is microbial dysbiosis ?
conditions changing mean shift in bacteria becoming pathogenic - disease promoting microbiotia
Besides microbial dysbiosis what is also important in periodontits ?
hyper inflammatory host response
individual patient
What type of microbiotia promotes periodontitis ?
synergistic
dysbiotic
shape the disease provoking microbiotia
Describe the microbial changes in periodontal disease ?
disordered collection aggregation interspecies interactions structured heterogenic communties keystone pathogens dysbiosis expression of virulence factors
How can we determine the subgingival microbiota ?
direct sampling from perio pockets
cultivation of samples
molecular techniques
What is the problem with trying to determine the species in subgingival plaque ?
most perio pathogens are anaerobic- when exposed to air cant culture
What is checkerboard hybridisation ?
DNA probes made for existing bacterial sequences
DNA taken from host and purified
probes used to identify which species are present
What does the intensity of the signal correlate with ?
the amount of organism
semi quantatative
What is the red complex ?
frequently associated with severe periodontal disease
What are the 3 organisms of the red complex ?
Porphyromonas.gingivalis
Tannerela.forsytha
Trepnoma.denticola
Which organisms are the initial colonisers in periodontal disease ?
Streptococcus- commensal
Which organisms are bridging organisms ?
fusobacterium nucleatum
What are the characteristics of F. Nucleatum ?
gram negative
proteolytic
anaerobic
long rod shaped
What does F . nucleatum do ?
forms co-aggregates
with early colonisers- strep
late colonisers- T. denticola
inavdes host epithelial cells
What are the characteristics of red complex bacteria ?
gram negative
proteolytic - destroy proteins in GCF
fastidious anaerobe
What is Porphyromonas gingivalis ?
short rods produces black/brown pigments using iron highly proteolytic adheres to oral streptococci keystone
What are keystone pathogens ?
disproprotionately important role in causing disease
What is tannerella forsytha ?
short rods tapered
difficult to grow in monoculture
possess a glycosylated S layer- hide from immune system
Why doesnt Kochs postulates apply to periodontitis ?
not culturable
not present in all cases of disease
more than 1 species involved
level rather than presence more important
What is the TM7 phlyum ?
frequently detected in subgingival dental plaque
elevated in mild perio
can grow when co-cultured- actinomyces odontlyctus
small genome- reflects dependence on others for growth
What are the adhesins of P.gingivalis ?
major fimbriae- adhesion and invasion
minor fimriae- coaggregation
What does the P.gingivalis capsule do ?
allows them to evade host immunity - phagocytosis and complement activation
What does the LPS of P.gingivalis do ?
it is potently inflammatory
What do P.gingivalis proteases do ?
extracellualr cysteine proteases-
cleave host proteins and collagens
major antigen in infection
What are the functions of Extracellular cysteine proteases ?
nutrition
processing
haemogluttinin
adhesion
What is AA ?
exception to the ecological plaque hypothesis
aggressive forms of periodontitis
facultative anaerobe
What is the function of AA ?
adhesion
impairment of host defence
tissue invasion
bone resorption
What is the function of AA adhesins ?
tight adherence by fimbriae and locii
bind to epithelial cells and enhance receptor medaited endocytosis
What are leukotoxins ?
pore forming toxin
targets immune cells expressing B2-integrin
What other AA toxins are there ?
cytolethal distending toxin
What is AA JP2 ?
clone associated with aggressive forms of periodontitis
storng leuukotixin activity
W.african adolescents
Are fungi eukaryotic or rokaryotic ?
eukaryotic
What are ascomycota ?
they can form ascospores
candida doesnt even though it is part of the ascomycota
What are basidiomycota ?
can cause disease - cryptococcus
What is the morphology of fungi ?
they grow as branched tubes called hyphae
What is the relative size of fungi ?
they are smaller than human cells but bigger than bacteria
What is the structure of the fungi cell wall ?
thick rigid cell wall
made of ergesterol rather than cholesterol
divided into 2 layers
What is the outer layer of the fungi cell wall like ?
amorphous
glycoproteins
carbohydrates
mannans
What is the inner layer of the fungi cell wall like ?
glucans and chitin
Why is the fungi cell wall important ?
for adherence and antigenicity
What is the carriage rate of candida ?
35-55%
What is the most common fungi species in the mouth ?
fungi
What are some members of the genus candida ?
candida albicans candida glaborata candida kruvei candida tropicalis candida dublineisis
Is the genus candida pathogenic ?
most non pathogenic
What does it mean if candida are dimorphic ?
they can transition between yeast and hyphal form
What is the significance of hyphae ?
they can be disease causing and invade epithelium
What does it mean if candida is opportunsitic ?
change in the environment
change in the gene expression and expression of virulence factors
What is the process of candida becoming pathogenic ?
normal commensals
change in environemntal conditions
candida proliferation
pathogenic and disease
What are the different morphologies of candida ?
hyphae
budding yeast
pseudohyphae and chlamydosphore
What is morphotype switching ?
swich between yeast and hyphal form
What is morphotype switching controlled by ?
osmotic shock temperature fluctuations pH nutrients oral bacteria salivary factors- statherin
Where can you find candida ?
in mixed species biofilms
amongst cocci and roda
How can bacteria influence candida ?
presence of bacteria can influence how they switch from hyphae to yeast
serum triggeres hyphae profuction
peptidoglycan can trigger hyphal formarion
How can Strep Gordonii influence hyphae ?
strep gordonii antigen I/II mediate binding to C.Albicans hyphae
How does Strep mutans influence hyphae ?
produces competence stimulating peptide which inhibits C.Albicans hyhae formation
What is competence stimulating peptide ?
allow transformation and DNA transfer
What type of relationships do oral bacteria have with C.Albicans ?
synergistic or competitive
Overall do Oral streptococci benefit or inhibit C.Albicans ?
benefit
Does lactobacillus inhibit or benefit oral bacteria ?
inhibit
What type of agar is Candida grown on ?
Sobarand dextrose agar
selects agaisnt bacteria due to low pH
Which candida species have true hyphae ?
albicans
dublineisis
Which differential agar is candida grown on ?
CHROMagar
different species have different morphologies
How else can we identify Candida species ?
using different carbohydrates
diff species have diff nutritional requirements
What are the virulence factors of candida ?
adherence morphology phenotype switching hydrolytic enzymes candidalysin
How does adherence work as a candida virulence factor ?
candida can adhere to epithelium or prostheses and resist saliva flow
produce adhesins
Which adhesins do candida produce ?
mannoproteins
fibrils
agglutinin like sequence proteins
hyphal wall protein
How does morphology act as a candida virulence factor ?
polymorphic/dimorphic
hyphae formation allows
oral epithelium invasion
evade pahgocytosis
Which factors are hyphae produced in response to ?
temperature
carbon dioxide
alkaline pH
How does phenotypic switching act as a candida virulence factor ?
change morphology in response to environmental stimuli
influence antigenicity, adhesion and drug susceptibility
Which hydrolytic enzymes do Candida produce ?
Aspartyl proteinases
phospholipases
What do aspartyl proteinases do ?
nutrtion cell morphology siwtching remove tissue barriers cleave immune proteins facilitate adherence
What do phsopholipases do ?
hydrolyse phospholipids leading to host cell membrnae damage
cell lysis
receptor exposure
What is candidalysin >
a lytic peptide that punches holes in epithelial cell
allows penetration of host tissue
What are some manifestations of candidasis ?
denture stomatitis
biofilm formation on surface of dentures
damage arises due to hyphal formation
neutrophil damage
What are some local factors that can make patients predisposed to candidasis ?
dentures
inhaled corticosteroid inhalers
reduced salivary formation
rich carb diet
What are some systemic factors that can make patients predisposed to candidasis ?
medication diabetes nutritional deficiency salivary gland hypofunction HIV age extermities
How can we diagnose oral candidosis ?
appearance- erethrema, white patches
lab tests- blood tests, oral swab, biopsy and histology
What are the primary forms of oral candidosis ?
acute pseudomembreanous candidosis
acute erythemous candidosis
chronic erythemous candidosis
chronic hyperplastic candidosis
What is acute pseudmembranous candidosis ?
red mucosa
plaques can be scraped off hard palate and tongue
inhaler use
What is acute eryhtemous candidosis >
painful red patches cracking of dorsum loss of filiform papillae due to antiobiotic sore mouth antibiotic use removes bacteria but leads to candida overgrowth
What is chronic erythemous candidosis ?
denture stomatitis
poorly fitting denture
no hyphae invasion
lack of OH
What are the treatment methods for denture stomatitis ?
wash dentures in chlorhexidine/sodium hypochlorite
leave dentures out as much as possible
What is chronic hyperplastic candidosis ?
candidal leukoplakia on sides of mouth heavy smokers can progress to malignancy cant be scraped off candidal hyphae invade epithelial layer
What are parasites ?
eukaryotic pathogens
Which parasites are part of the excavata group ?
leismania
trichomonas tenax
Which parasites are part of the amoebozoa ?
entamoeba gingivalis
What is symbiosis ?
association between organisms from different species
What is mutualism ?
both partners benefit from interaction and are co-dependent for thriving
What is commensalism ?
one partner benefits whereas the other is neither harmed nor receives benefit
What is parasitism ?
one partner relies on the host for nutrients and shelter at cost to the host and leads to host damage
What are obligate symbionts ?
can only live together in symbiosis
highly adapted to body sites in one host
most parasitic protozoa are obligate symbionts and require a host to complete their life cycle
What are facultative pathogens ?
they dont cause disease all the time
What are opportunstic pathogens ?
cause pathologies when the host is compromised
In which situations can the host be compromised ?
AIDS
immunodeficinecy
malnutrition
chemotherapy
Which are the best adapted parasites ?
the ones that are least pathogenic and dont harm their host
Which 2 functions must the mucosa mediate ?
protect the individual from insults- microbial, chemical and physical
facilitate exchange
Which interactions are required for healthy mucosa ?
microbes interact with epithelial cells and with immune cells
What are supraorganisms ?
interactions between human and microbial cells
What is a eubiotic microbiotia ?
promotes health
What is a dysbiotic microbotia ?
promotes diseases
abnormal, micorbial and taxonomic structures lead to pathologies
even in the absence of pathogens
What are pathobionts ?
members of the microbiotia that have the potential to cause damage
What does monexenous mean ?
parasite requires a single host for life cycle completion
T.tenax
E.gingivalis
What does heteroxenous mean ?
two or more hosts required for completion
1 host is intermediate for development other is definite for sexual development
Leishmania
What does promiscuous mean ?
infect broad range of hosts
T.tenax
What are zoonoses ?
human disease caused by animal parasites
animals are reservoirs for human pathogens
Which archaea are in the oral cavity ?
methanobrevibacter
Which microbial eukaryotes are present in the oral cavity ?
fungi
microbial parasites- T.tenx/E.gingivalis
What are autochtnous microbiotia >
characteristically found at a particular site
adapted to grow in the cavity
T.tenax and E.gingivalis
What are allocthnous micrbiota ?
transiently present due to host compromise
What is the route of transmission of Leishmania ?
sand flies
What are the 3 main pathobiologies of Leishmania ?
cutaneous leishmania- most common. skin lesions etc
visceral leishmania- fever, weight loss, spleen and liver
mucocutaeneous leishmania- destruction of mucous membranes- requires nose, mouth entry
What are 2 common microbial eukaroyotes assocaited with periodontitis ?
T.tenax
E.gingivalis
What are the types of Trichmonas ?
Trichomonas vaginalis
trichomonas gallinae
trichomonas tenax
Which eukaroyte is found in the periodontal pcoket ?
t.tenax
How is E.gingivalis transmitted ?
foecal oral route
What is the relationship between E.gingivalis and periodontits ?
could target homeostatic bacteria
direct contributor to inflammation
What are the 4 types of anti fungal drugs ?
polyenes
azoles
5-flucoytosine
echinocadnins
What are polyenes ?
nystain
disrupt fungal cell membranes by interacting eith ergesterol and making the membrane leaky
topical
What are azoles ?
miconazole
inhibit ergesterol biosynthesis
topical and systematic
What is 5-flucocytosine ?
inhibt DNA and protein synthesis
systematic
What are echinocardins ?
inhibt Beta 1-3 D-glucan aynthesis
intravenous
microfungin
What must be considered with anti-fungal medication ?
fungi are slow growing- long course of treatment
consider other drugs being given
What are dental abscesses ?
collection of pus which is walled off by a barrier of inflmmatory reaction
How can abscesses develop ?
confined space that bacteria can gain entry to and multiply
What is a dentoalveolar abscess ?
pulp death due to bacterial invasion as a result of dental caries
What are the routes of infection for a dentoalveolar absecess ?
exposed dentine tubules pulp exposure bacteremia root fracture endodontic infection
What is an endodontic infection ?
infected pulp
What does root canal treatment do ?
clean out the canals and seal them to prevent bacterail access
Which chemicals are used to clean out root canals ?
sodium hypochlorite
chlorhexdine
calcium hydroxide
iodine
Which species are resistant to root canal treatment ?
enterococcus faecialis
result in flare ups
What is a periodontal abscess ?
differentiated from dentoalveoalr due to a vital pulp
How does periodontal abscess develop ?
foreign material in an estabished periodontal pocket
leads to swelling, eryhtrema and pus at gingival margin
Species associated with periodontal abscesses ?
porphyromonas
fusobacterium
actinomyces
haemolytic strep
How can we treat a dentoalveoalr abscess ?
local measures- RSI and scaling
irrigation of root canal
antispetics - chlorhexidine mouthwash
extraction
Which bacteria are present in dental abscesses ?
usually anaerobes- facultative and strict
Which facultative anaerobes can you find in dental abscesses ?
viridans strep
saphy
strep anginosus
Which obligate anaerobes can be found in dental abscesses ?
fusobacterium
preveotella
T. denticola
What are factors that can affect bacterial populations in abscesses ?
oxygen tension
availability of nutriets like proteins
bacterial interactions
Why might you find bacterial popualtions with 3/4 species ?
multiple infection but only certain species survive
one species infects and paves the way for others
What does coaggregation lead to ?
coinvasion of epithelial cells or dentine tubules
What is an example of coinvasion into epithelial cells ?
Fusobacterium nucleatum aggreagates with S.cristatus into cells
What is an example of coinvasion into dentine tubules ?
P.gingivalis and S.gordonii
What are localsied spreads of infection ?
soft tissue abscesses
cellulities- inflammation spreads through connetive tissue
What are extreme spreads of infection >
sinuses
osteomyelitis
adjacent fascial layers
maxillary sinus
What is osteomyelitis ?
inflammation of the medullary bone - maxill and mandible
posterior extension to the cortical bone and the periosteum
What are typical isolates found in osteomyelitis ?
obligate anaeroboes
actinomyces
What are treatment optiond for osteomyelitis ?
local debridement
topical antispetic
antibiotics
Give some examples of tissue sapces ?
pterygomandibualr space
lateral pharyngeal space
sublingual, submandibular, submental
Where can infection from 1-6 go ?
sublingual space
Where can infection from 1-3 go ?
submental space
Where can infection from 6-8 go ?
buccal space
Where can infection from an 8 go ?
submasseteric space pterygomandibular space lateral pharyngeal space retropharyngeal space mediastinum
How can we treat dental abscesses ?
local measures drain pus tooth extraction drain root canals devride infected periodontal pocket irrigate operculum
When do you prescribe antibiotics ?
evidence of spreading infection
systemic involvement
When is there evidence of spreading infection ?
lymph node involvement
swelling
lockjaw
When is there evidence of systemic involvement ?
fever
dysphagia
malaise
temp over 38
What are warning signs ?
raising of tongue elevated floor of mouth neck swelling fever voice hoarosness breathing difficulty
Which antibiotics can be presribed for infections ?
metronidazole
amoxicillin
What is ludwigs angina ?
progression of dentoalveolar infection to tissue spaces
neck swelling
difficulty breathing
to mediastinum
Which bacteria are involved in Ludwigs angina ?
prevotella
porporymonas
fusobacterium
anaerobic strep
What is pericoronitis ?
superficial infection of operculum
usually lower 8s
local sprea of infection
infection in space between tooth and overlying tissue
Which anaerobic bacteria are involved in pericoronitis ?
p.intermdium
anaerboc streptococci
fusobacterium
A.actinomycecomitans
How can we manage pericoronitis ?
locla measures
irrigation
extraction
metronidazole if systemic
What is cerviofacial actinmycosis ?
opportunsitic infectin caused by Actinomyces- A.isrealii
submandibular swelling/ angle of mandible swelling
thick yellow pus granules - sulphur granules
What are the visible granules in C.actinomycosis ?
calcified aggregates of actinomyces filaments
What is ANUG ?
poor OH, stress, immunocompromised, smokers
grey pseudomembrane - superficial infection of gingival margin
treponema and prevotella
How can we treat ANUG ?>
OHi improvement
remove supra/subgingival plaque dpeosits
scaling
ultrasonic debridment
What are seocndary forms of oral candidosis ?
angualr cheilitis
median rhomboid glossitis
chronic mucocutaenous candidosis
What causes angualr cheilitis ?
candida
staph
strep
What is angualr cheilitis ?
lesions that affect the angles of the mouth
bilatera
soreness
eryhthema
What causes denture related angualr cheilitis ?
candida from mouth
Where do staphylocci originate in angualr cheilitis ?
anterior part of nose
If angualr cheilitis is fungal how do we treat ?
miconazole cream
If angualr cheilitis is bacterial how do we treat ?
sodium fusidate
What is median rhomboid glossitis ?
shape on dorsum of tongue
atrophy of filiform papillae
smoking and inhaled steroids are cause
What is chronic mucocutanous candidosis ?
imapired cellular immunity agaisnt candida
assocaited with rare congenital disorders
What is the relationship between diabetes mellitus and periodontal disease ?
increased periodontal disease with diabetes
periodontal inflammation may impact glycaemic control
What is the relationship between periodontal disease and adverse pregnancy reactions ?
periodontal disease linked with preterm babies
F.nucleatum and P.gingivalis found in preterm baby amniotic fluid
What is the association between cardiovascualr disease and Periodontitis ?
periodontal disease leads to increased inflammation
atheroscleorsis - P. gingivalis and F.nucleatum maintain inflmmation sites like plaque
What does inflammatory periodontal disease lead to ?
cytokine production
LPS exposure
What are the sources of Hallitosis ?
85-90% oral
5-10% nose
3% tonsils
1% other
What are oral causes of halitosis ?
poor OH gingivitis and periodontal disease oral infections unclean dentures xerostomia smoking dental abscesses
What are the causes of xerostomia ?
mouth breathing fasting prolonged talking stress salivary gland hypofucntion
What are some bacterial niches where halitosis can originate ?
posterior dorsum of the tongue
gingival sulcus
pockets
interdental spaces
Where else can halitosis originates ?
oral candidosis and oral tumours
Why is the tongue a bacterial niche ?
tongue coating has deep fissures
bacteria can adhere and avoid saliva flushing
create anaerobic environment
What type of bacteria are prominent with hallitosis ?
gram negative anaerobes
What are the most active bacteria in hallitosis ?
P.gingivalis
T.denticola
Tannerella Forsythia
What is hallitosis primarily caused by ?
degradation of sulfur containing amino acids derived from proteins from exofoliated epithelial cells, plaque or blood.
What are some VSCs ?
hydrogen sulphide
dmethylsulphide
What are some non sulfur compounds that dont cause hallitosis ?
skatole
cadaramine
How can we assess halitosis ?
assess smell of breath, floss and tongue scrapes
use gas chromatography- sensitive to hydrogen sulphide
use BANA - detect periodontal pathogens
What arguments are for an association between peridontal disease and halitosis ?
gram negative microorganisms that cause hallitosis are associated with periodontal disease
Halitosis found in those with periodontitis
elevated VSCs in pockets 4mm+
What are the arguents against relationship between periodontitis and halltosis ?
periodontally healthy patients have hallitosis
tongue dorsum is main cause
periodontally pockets are partially sealed which prevent gas transfer
tongue cleaning reduces VSCs
How can we treat hallitosis ?
mask the malodour
reduced the bacteria mechanically and nutrients
chemical reduction of microbe load- mouthwashes
oxidising agents like chlorine dioxide which degrade VSCs and make them non volatile
What is FAA agar ?
cultivation of fastiduous anaerobic microorganism
selective if you add antiobiotics vancomycin and neomycin
Why is there a low level of glucose in FAA agar ?
prevents alcohol and acid production
also essential growth factor for anaerobes
What does reduced transport fluid do ?
provides anaerobic conditions acting as a reducing agent
Is FAA selective or indicative ?
indicative
selective if you add antibiotics
What is MSB ?
with tellurite omitted it is selective for S.Mutans and sobrinus
indicative as well
What is TYCS ?
tryptone
yeast
cysteine
sucrose
What does TYCS do ?
used to differentiate strep mutans from sanguis
uses high sucrose content to promote glucan formation by S Mutans which will form distinctive colonies
Is TYCS selective or indicative ?
both
seletive for mutans but indicative of mutans and salivarius
What is blood agar ?
nutrient rich non selective medium
Which bacteria are common around mouth and nose ?
staphylococci- non haemolytic
What is alpha haemolysis ?
green colour change as hydrogen peroxide vlrach the heaemoglobin in the blood agar
What is beta haemolysis ?
complete lysis of RBCs
light colour
What is gamma haemolysis ?
no haemolysis
What is chlorhexidine mouthwash used for ?
reduces potentially pathogenic flora to a minimum to allow re establishment of a healthy balance
used in periodontal patients and pre surgery
What does the snyder test detect ?
acidogenic and aciduric bacteria
potential indicative caries test
What does the snyder medium contain ?
2% glucose and bromescol green
Which bacteria are detected in the snyder test ?
lactobacilli - found in carious lesions as there is a low pH in carious lesions- selective
Which carbohydrate do bacteria ferment in the snyder test ?
glucose into lactic, acetic and formic acid
Why does P.gingivalis form dark colonies on blood agar ?
contains porphoryn pigments that contain haem
prevotella also does this
The antibiotics vancomycin and neomycin added to FAA are selective for which bacteria ?
fusobacterium
What is the selective agent in MSB agar ?
bacitracin- selective for S.mutans
How do you work out CFU/ml ?
number of colonies x dilution factor/ volume of culture plate
Why is CFU not the same as number of cells in a culture ?
CFU contains dead cells
multiple cells can make a CFU
What is staph agar ?
selects for staphylococci by having a high NaCl concentration
What is McConkey agar ?
selects for enterobacteria like e.coli
high concentration of bile salts
What is candida agar ?
low pH , chloramphericol
selects for canddia as they tolerate a low pH in the mouth and vagina
What is bacictracin ?
an antibiotic
s.sonrinus and mutans are resistant to it so they can be selected for using it
