Bacteria- Oral Bacteria A Flashcards
how many species are present in the oral cavity
more than 700
what are the sampling methods of oral bacteria
-collect saliva
- tongue blade
- scrape from tooth surface
- wick fluid from deep pockets (endodontic paper)
what do molecular techniques in identifying oral bacteria often target
16S rRNA genes
what is the gold standard in identifying oral bacteria
16S rRNA gene sequencing
describe DNA identification using PCR
-species specific primers
- 16S rRNA gene sequence
describe DNA hybridization assays
whole genome, species specific probes
- species specific 16S probes
- DNA microarrays
what can 16S sequence analysis do
identify new species in a sample
what are the types of direct observation of bacteria by microscopy
- gram staining
- species specific staining
- fluorescent antibody labeling
- fluorescence in situ hybridization (FISH)
describe dental plaque
-biofilm on tooth surface
- one of the highest concentrations of bacteria in the body
- colonizing bacteria interact with acquired pellicle
describe the process of formation of dental plaque
- tooth surface is coated with an acquired pellicle
- passive transport of bacteria to pellicle surface
- subsequent attachment of these species and other bacterial species occurs by coaggregation
- microenvironment created that supports additional species
- glucan production
- oxygen levels drop
- get some detachment of bacteria and colonization of new sites
what makes up the dental biofilm composition
- molecules in saliva
- material shed from bacterial cell surfaces
-polymers from GCF
what are the common streptococcus species that initially colonize the oral cavity
- strep gordonii
- strep oralis
- strep mitis
- strep sanguis
what do adhesins on bacterial surface bind to
receptors in the pellicle
what are pellicle receptors
polymers from saliva and bacteria
adhesion is usually ______
irreversible
what are the adhesins on streptococcus and what do they bind
-Antigen I/II
- bind human salivary glycoproteins, other bacteria and calcium
what is occuring during sebseuqent attachment of these species and other bacterial species by coaggregation and what are the species
- bacteria binding to other bacteria
- additional bacteria bind to early binding bacteria and to each other
- multiple species coaggregate
- actinomyces naeslundii
- actinomyces viscous
- streptococcus gordonii
what bacteria start to multiply in the developing biofilm
-streptococcus mutans
- streptococcus sobrinus
what do streptococci produce in glucan production
glucosyltranferases
what are glucans
branched chain polysaccharides
what are the glucans produced in glucan production
- alpha 1->6 linkage
- alpha 1->3 linkage
what binds to glucans
bacteria
what are the obligate anaerobes that colonize when oxygen levels drop
- prevotella melaninogenicus
- prevotella oralis
- veillonella spp
where do the obligate anaerobes colonize in the oral cavity when oxygen levels drop
- between teeth and dental gingival crevice
how do bacteria detach and colonize new sites
bacteria will shed or degrade their adhesins
what are the altered properties of bacteria in a biofilm
- up regulation of genes for extracellular polysaccharide synthesis
- increased resistance to antimicrobial agents
- metabolic interaction between closely spaced bacteria
describe the ways bacteria acquire increased resistance to antimicrobial agents
- restricted penetration of agent into biofilm
- inactivation of agents by enzymes concentrated in biofilm
- slow growth rate of bacteria in biofilm
- expression of novel surface associated phenotypes
what are the types of metabolic interactions between closely spaced bacteria and describe each
-synergistic: degradation of complex nutrients
- antagonistic- bacteriocins
what is the composition of dental plaque in fissures
-sparse flora and mainly gram positives
-streptococci predominate
what is the composition of dental plaque in gingival crevice
- greater numbers of bacteria and more diverse
- includes many gram negative and anaerobic species
what is the composition of approximal plaque
- bacteria composition is in betweeh above 2
- complex composition but more than 50% are streptococci and actinomyces
what is the main nutrient source in fissures
saliva
what is the main nutrient source in gingival crevice
- crevicular fluid
what is the difference of redox potential in gingival crevice vs fissures
lower in gingival crevice
plaque eventually reaches a ________
microbial homeostasis
how does breakdown of homeostasis alter bacterial composition
-reduction in saliva flow
- increased consumption of sucrose
what can result in breakdown of homeostasis
caries
what is the main bacteria involved in caries development
mutans streptococci
what acids are produced from fermentation in biofilm
-lactic acid mostly
- also acetic acid and formic acid
how does acid demineralize teeth
-solubilizes calcium and phosphate
- get reprecipitation when pH increases
what is the brief mechanism of caries formation
- sucrose and glucosyltransferases (TGFs) are required for accumulation of mutans streptococci
- the mutans streptococcal adhesin (known as antigen I/II) interacts with galactosides
- glucan binding protein is also present
- metabolism of saccharides results in formation of lactic acid
gingival recession occurs with _____
age
what percentage of individuals over 60 have root caries
60%
what are the likely pathogens of root caries
MS and lactobacilli
- actinomyces viscosus and actinomyces naeslundii
what are the pathogenic properties of cariogenic abcteria
-rapidly transport fermentable sugars/convert to acid
- rapid compared to other plaque bacteria
-cariogenic bacteria have multiple sugar transporters including PEP-PTS systems
- group translocation
- production of extracellular and intracellular polysaccharides
- ability to maintain sugar metabolism under extreme conditions
what is group translocation
molecule transported into the cell while being chemically altered
what extracellular and intracellular polysaccharides are produced
-glucans and fructans
- intracellular storage- allows acid production even when sucrose is not available
how are bacteria able to maintain sugar metabolism under extreme conditions
- maintain a favorable intracellular environment by pumping out protons even into acidic surroundings
- bacterial enzymes have more acidic pH optima
- produce acid stress response proteins to protect cell contents
what microbes tolerate acidic conditions
MS and lactobacilli
what is a notable property of noncariogenic bacteria
alkali production
what are the major substrates for alkali production and what do they generate
urea and arginine
- ammonia NH3
what are peridontal diseases
inflammatory processes that occur in the tissues surrounding the teeth in response to bacterial accumulations on the teeth
what is the results of periodontal diseases
progressive loss of collagen attachment of the tooth to the alveolar bone, loss of supporting alveolar bone, and tooth loss
what is the measurement of a periodontal pocket and how much bacteria is in it
- 4-12 mm in depth
- 10^7 - 10^ 9 bacteria
what is gingivitis
gingival inflammation without bone loss about teeth
- no pockets deeper than 3 mm
what percentage of adults have gingivitis around 3 or 4 teeth
50%
what percentage of adults have periodontitits
30%
what is the non specific plaque hypothesis
disease is due to the host response to non specific growth of bacteria on tooth surfaces - inflammatory disease
what is the specific plaque hypothesis
disease is due to a limited number of species which produce biologically active molecules that are proinflammatory or antigenic - infection
describe the non specific plaque hypothesis
- traditional view
- bacterial complexity of dental plaque
- non specific mechanisms of generating inflammatory response- LPS, volatile fatty acids, sulfides
- treatment dictates that flora be suppressed
describe the specific plaque hypothesis
- localized juvenile periodontitis
- acute necrotizing ulcerative gingivitis
what is the prevalnce of localized juvenile periodontitis and what microbe causes it and how is it treated
- 1-5 out of 100 teenagers
- aggregatibacter actinomycetemcomitans
- produces LT that inhibits neutrophils
- treated with tetracycline
when was acute necrotizing ulcerative gingivitis common, what is the microbe that causes it, and whats the treatment
- trench mouth of world war 1
- spirochetes and fusobacterium nucleatum
- antibiotic mouth rinses with oxidizing agents or metronidazole
what are the microbes involved with specific plaque hypothesis
- porphyromonas gingivalis
- tannerella forsythia
- treponema detnicola
fimbriae allows adhesion to:
-saliva coated hydroxyapatite
- human oral epithelial cells
what are the virulence factors for porphyromonas gingivalis
- fimbriae
- hemagglutinins
- capsule prevents phagocytosis
- 3 major proteolytic activites: trysin like, collagenolytic, and glycylprolyl peptidase
what is the best example of a keystone pathogen
porphyromonas gingivalis
what are the virulence factors for aggregatibacter actinomycetemcomitans
-leukotoxin
- invasins
- bacteriocin
what do invasins do
aids in bacteria penetrating eukaryotic cells
what does bacteriocin do
inhibition of growth or killing of other bacterial species, streptococcus sanguis and actinomyces viscous
what is aggregatibacter actinomycetemcomitans immunoinhibitory virulence associated characteristic and what does it do
- capsular polysaccharide- resistance to phagocytosis by PMNs, reduction in complement dependent response by PMNs increase in bone resorption
- phospholipase C- hydrolyzation of host cell membrane
what are the fusobacterium nucleatum virulence factors
- hemolysin
- leukocidin
- capsule
- superoxide dismutase
what are the virulence factors for prevotella intermedia
- the brown or black pigment
- collagenase, hyaluronidase and protease
- hemolysin
what does the brown or black pigment in prevotella intermedia do
defensive barrier to protect bacteria from toxic effects of oxygen
what does hemolysin do
favors the acqusition of iron
