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Microbiology > Bacteria- Oral Bacteria A > Flashcards

Bacteria- Oral Bacteria A Flashcards

1
Q

how many species are present in the oral cavity

A

more than 700

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2
Q

what are the sampling methods of oral bacteria

A

-collect saliva
- tongue blade
- scrape from tooth surface
- wick fluid from deep pockets (endodontic paper)

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3
Q

what do molecular techniques in identifying oral bacteria often target

A

16S rRNA genes

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4
Q

what is the gold standard in identifying oral bacteria

A

16S rRNA gene sequencing

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5
Q

describe DNA identification using PCR

A

-species specific primers
- 16S rRNA gene sequence

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6
Q

describe DNA hybridization assays

A

whole genome, species specific probes
- species specific 16S probes
- DNA microarrays

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7
Q

what can 16S sequence analysis do

A

identify new species in a sample

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8
Q

what are the types of direct observation of bacteria by microscopy

A
  • gram staining
  • species specific staining
  • fluorescent antibody labeling
  • fluorescence in situ hybridization (FISH)
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9
Q

describe dental plaque

A

-biofilm on tooth surface
- one of the highest concentrations of bacteria in the body
- colonizing bacteria interact with acquired pellicle

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10
Q

describe the process of formation of dental plaque

A
  • 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
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11
Q

what makes up the dental biofilm composition

A
  • molecules in saliva
  • material shed from bacterial cell surfaces
    -polymers from GCF
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12
Q

what are the common streptococcus species that initially colonize the oral cavity

A
  • strep gordonii
  • strep oralis
  • strep mitis
  • strep sanguis
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13
Q

what do adhesins on bacterial surface bind to

A

receptors in the pellicle

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14
Q

what are pellicle receptors

A

polymers from saliva and bacteria

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15
Q

adhesion is usually ______

A

irreversible

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16
Q

what are the adhesins on streptococcus and what do they bind

A

-Antigen I/II
- bind human salivary glycoproteins, other bacteria and calcium

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17
Q

what is occuring during sebseuqent attachment of these species and other bacterial species by coaggregation and what are the species

A
  • 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
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18
Q

what bacteria start to multiply in the developing biofilm

A

-streptococcus mutans
- streptococcus sobrinus

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19
Q

what do streptococci produce in glucan production

A

glucosyltranferases

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20
Q

what are glucans

A

branched chain polysaccharides

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21
Q

what are the glucans produced in glucan production

A
  • alpha 1->6 linkage
  • alpha 1->3 linkage
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22
Q

what binds to glucans

A

bacteria

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23
Q

what are the obligate anaerobes that colonize when oxygen levels drop

A
  • prevotella melaninogenicus
  • prevotella oralis
  • veillonella spp
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24
Q

where do the obligate anaerobes colonize in the oral cavity when oxygen levels drop

A
  • between teeth and dental gingival crevice
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25
Q

how do bacteria detach and colonize new sites

A

bacteria will shed or degrade their adhesins

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26
Q

what are the altered properties of bacteria in a biofilm

A
  • up regulation of genes for extracellular polysaccharide synthesis
  • increased resistance to antimicrobial agents
  • metabolic interaction between closely spaced bacteria
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27
Q

describe the ways bacteria acquire increased resistance to antimicrobial agents

A
  • 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
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28
Q

what are the types of metabolic interactions between closely spaced bacteria and describe each

A

-synergistic: degradation of complex nutrients
- antagonistic- bacteriocins

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29
Q

what is the composition of dental plaque in fissures

A

-sparse flora and mainly gram positives
-streptococci predominate

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30
Q

what is the composition of dental plaque in gingival crevice

A
  • greater numbers of bacteria and more diverse
  • includes many gram negative and anaerobic species
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31
Q

what is the composition of approximal plaque

A
  • bacteria composition is in betweeh above 2
  • complex composition but more than 50% are streptococci and actinomyces
32
Q

what is the main nutrient source in fissures

A

saliva

33
Q

what is the main nutrient source in gingival crevice

A
  • crevicular fluid
34
Q

what is the difference of redox potential in gingival crevice vs fissures

A

lower in gingival crevice

35
Q

plaque eventually reaches a ________

A

microbial homeostasis

36
Q

how does breakdown of homeostasis alter bacterial composition

A

-reduction in saliva flow
- increased consumption of sucrose

37
Q

what can result in breakdown of homeostasis

A

caries

38
Q

what is the main bacteria involved in caries development

A

mutans streptococci

39
Q

what acids are produced from fermentation in biofilm

A

-lactic acid mostly
- also acetic acid and formic acid

40
Q

how does acid demineralize teeth

A

-solubilizes calcium and phosphate
- get reprecipitation when pH increases

41
Q

what is the brief mechanism of caries formation

A
  • 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
42
Q

gingival recession occurs with _____

A

age

43
Q

what percentage of individuals over 60 have root caries

A

60%

44
Q

what are the likely pathogens of root caries

A

MS and lactobacilli
- actinomyces viscosus and actinomyces naeslundii

45
Q

what are the pathogenic properties of cariogenic abcteria

A

-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

46
Q

what is group translocation

A

molecule transported into the cell while being chemically altered

47
Q

what extracellular and intracellular polysaccharides are produced

A

-glucans and fructans
- intracellular storage- allows acid production even when sucrose is not available

48
Q

how are bacteria able to maintain sugar metabolism under extreme conditions

A
  • 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
49
Q

what microbes tolerate acidic conditions

A

MS and lactobacilli

50
Q

what is a notable property of noncariogenic bacteria

A

alkali production

51
Q

what are the major substrates for alkali production and what do they generate

A

urea and arginine
- ammonia NH3

52
Q

what are peridontal diseases

A

inflammatory processes that occur in the tissues surrounding the teeth in response to bacterial accumulations on the teeth

53
Q

what is the results of periodontal diseases

A

progressive loss of collagen attachment of the tooth to the alveolar bone, loss of supporting alveolar bone, and tooth loss

54
Q

what is the measurement of a periodontal pocket and how much bacteria is in it

A
  • 4-12 mm in depth
  • 10^7 - 10^ 9 bacteria
55
Q

what is gingivitis

A

gingival inflammation without bone loss about teeth
- no pockets deeper than 3 mm

56
Q

what percentage of adults have gingivitis around 3 or 4 teeth

A

50%

57
Q

what percentage of adults have periodontitits

A

30%

58
Q

what is the non specific plaque hypothesis

A

disease is due to the host response to non specific growth of bacteria on tooth surfaces - inflammatory disease

59
Q

what is the specific plaque hypothesis

A

disease is due to a limited number of species which produce biologically active molecules that are proinflammatory or antigenic - infection

60
Q

describe the non specific plaque hypothesis

A
  • 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
61
Q

describe the specific plaque hypothesis

A
  • localized juvenile periodontitis
  • acute necrotizing ulcerative gingivitis
62
Q

what is the prevalnce of localized juvenile periodontitis and what microbe causes it and how is it treated

A
  • 1-5 out of 100 teenagers
  • aggregatibacter actinomycetemcomitans
  • produces LT that inhibits neutrophils
  • treated with tetracycline
63
Q

when was acute necrotizing ulcerative gingivitis common, what is the microbe that causes it, and whats the treatment

A
  • trench mouth of world war 1
  • spirochetes and fusobacterium nucleatum
  • antibiotic mouth rinses with oxidizing agents or metronidazole
64
Q

what are the microbes involved with specific plaque hypothesis

A
  • porphyromonas gingivalis
  • tannerella forsythia
  • treponema detnicola
65
Q

fimbriae allows adhesion to:

A

-saliva coated hydroxyapatite
- human oral epithelial cells

66
Q

what are the virulence factors for porphyromonas gingivalis

A
  • fimbriae
  • hemagglutinins
  • capsule prevents phagocytosis
  • 3 major proteolytic activites: trysin like, collagenolytic, and glycylprolyl peptidase
67
Q

what is the best example of a keystone pathogen

A

porphyromonas gingivalis

68
Q

what are the virulence factors for aggregatibacter actinomycetemcomitans

A

-leukotoxin
- invasins
- bacteriocin

69
Q

what do invasins do

A

aids in bacteria penetrating eukaryotic cells

70
Q

what does bacteriocin do

A

inhibition of growth or killing of other bacterial species, streptococcus sanguis and actinomyces viscous

71
Q

what is aggregatibacter actinomycetemcomitans immunoinhibitory virulence associated characteristic and what does it do

A
  • 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
72
Q

what are the fusobacterium nucleatum virulence factors

A
  • hemolysin
  • leukocidin
  • capsule
  • superoxide dismutase
73
Q

what are the virulence factors for prevotella intermedia

A
  • the brown or black pigment
  • collagenase, hyaluronidase and protease
  • hemolysin
74
Q

what does the brown or black pigment in prevotella intermedia do

A

defensive barrier to protect bacteria from toxic effects of oxygen

75
Q

what does hemolysin do

A

favors the acqusition of iron

Microbiology (39 decks)

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