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BDS3 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Before colonising the subgingival region, anaerobes might stay where in the oral cavity?

A

The tongue.

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2
Q

True or false: We still need to upkeep OH even if we don’t eat anything orally (e.g. tube fed)

A

True, the bacteria feed mainly on nutrients in our saliva (e.g. desquamated cells)

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3
Q

True or false: There is less diversity on the smooth surfaces of the teeth than there is on the tongue.

A

True, only bacteria that can adhere to the smooth surface are allowed to stay.

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4
Q

What is hemin?

A

Hemin is a breakdown molecule from haemoglobin, used as a protein nutrient (e.g. for P.Gingivalis)

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5
Q

What is the main difference in components for resting vs. stimulated saliva?

A

Bicarbonate content much higher in stimulated vs. non-stimulated.

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6
Q

What is the main difference in components between GCF and saliva?

A

GCF is much higher in proteins and IgA/G.

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7
Q

Bacteria die faster in hot or cold?

A

Hot

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8
Q

True or false: A facultative anaerobe can still survive in O2 but would much prefer no O2.

A

True

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9
Q

Why might a group of bacteria of differing species thrive better than a lone species of bacteria?

A

Different species can break different glycosidic bonds, so each are able to make CHOs more accessible to the others.

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10
Q

If you wanted to lower someone’s caries risk, what is the way you would change their carbohydrate intake?

A

Lower the frequency rather than the amount

although lowering amount would be nice too, but wont have as much impact on caries risk

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11
Q

What is considered to be the most cariogenic sugar?

What is it made up of?

A
  • Sucrose

- Made from glucose and fructose

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12
Q

What are FOUR things milk may do to protect teeth?

A
  • Buffering
  • Ca and PO4 for remin
  • Reduce adherence of S.mutans to pellicle
  • Reduce absorption of GTF to pellicle
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13
Q

What are the active ingredients in Colgate Total (12-hour)?

A
  • Triclosan (antibacterial)
  • Copolymer (aids in retention of triclosan)
  • NaF (fluoride source)
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14
Q

Name TWO main facultative anaerobe rods.

A
  • Actinomyces

- Lactobacillus

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15
Q

What are the TWO types of actinomyces?

Which is the most common?

A
  • A. Naeslundii (most common)

- A. Israelii

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16
Q

What are TWO features of A. naeslundii?

A
  • Produces extracellular polymer from sucrose

- Two types of fimbrae (co-aggregation and attachment)

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17
Q

What can A. Israelii cause?

A

Actinomycosis (lumpy jaw)

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18
Q

What is the difference between actinomyces and lactobacillus in terms of presence in plaque?

A
  • Actinomyces is commonly found in plaque (pioneer - first bacteria to attach to pellicle)
  • Lactobacillus is mainly found in cariogenic plaque
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19
Q

True or false: lactobacillus can use both homofermentation and heterofermentation.

A

True.

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20
Q

True or false: propionic bacteria is stronger than lactic acid

A

False.

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21
Q

True or false: Rothia Dentocariosa is a large contributor to caries.

A

False.

it may be implicated in infective endocarditis

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22
Q

Eubacterium is asaccharolytic and non-proteolytic, so it relies on other bacteria to breakdown proteins for it. What is ONE mechanism through which it can produce a more favourable environment for proteolytic bacteria?

A

It produces H2 which reacts with O2 to form H2O (reducing O2 in the environment). This will encourage growth of anaerobic proteolytic bacteria. (seen in advanced periodontal disease)

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23
Q

What is one of the most common bacteria found in subgingival plaque?

A

Eubacterium (up to 50%)

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24
Q

What is the most dominant bacteria in the mouth?

A

Streptococci (found on hard and soft tissues)

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25
Q

What are the THREE main groups of strep and their roles in oral pathology.

A
  • Strep mutans (caries)
  • Strep salivarius (soft tissues)
  • Strep mitis (pioneer colonisers)
26
Q

What are the TWO main species in the strep mutans group?

A
  • Strep mutans

- Strep sobrinus (previously categorised as S.mutans)

27
Q

What does it mean when a bacteria is capnophilic?

A

It can survive in the presence of high conc CO2.

28
Q

What are THREE metabolic features of s.mutans that make this acidogenic/aciduric bacteria cariogenic?

A
  • Produces soluble and insoluble extracellular polysaccharides from sucrose
  • Produces intracellular polysaccharides (for energy storage)
  • It can metabolise sorbitol (e.g. chewing gum) and mannitol
29
Q

What is the difference between s.mutans and lactobacillus in terms of where we would find them?

A
  • S.mutans in carious lesions throughout all stages

- Lactobacillus found in cavitated lesions

30
Q

What is the main difference between s.mutans and s.sobrinus?

A

S.sobrinus is sensitive to bacitracin antibiotic (used in selective agar medium)

31
Q

What are the THREE main types of strep from the Mitis-group?
What are their virulence factors?

A
  • S.sanguis (EPS, IgA protease)
  • S.gordonii (EPS, binds to amylase)
  • S.oralis (EPS, neuraminidase, IgA protease)
32
Q

What strep species has neuraminidase activity and what is its function?

A

S.oralis
- Neuraminidase cleaves off the sialic acid ‘cap’ on epithelial cells and salivary mucins to expose a more easily metabolised sugar molecule so that other bacteria can start to break the sugar down.
NOTE: A. naeslundii and F. nucleatum also produce neuraminidase

33
Q

What strep species binds to amylase and what is its function?

A

S.gordonii

- Binding to amylase shields it for protection and breaks down carbohydrates for nutrition.

34
Q

What is symbolic of porphyromonas on blood agar?

A 
Black pigmented (turns black on blood agar)
- is also asaccharolytic
35
Q

What are THREE similarities and ONE difference between porphyromonas and prevotella?

A

Similarities

  • Anaerobic
  • Gram -ve rods
  • Require hemin (both play a role in periodontitis)

Differences
- Prevotella can metabolise glucose, while porphyromonas is asaccharolytic.

36
Q

What is ONE example of a fusobacterium?
Where can it be found?
What is its most significant ability?

A
  • F. nucleatum
  • Plaque in health and disease
  • Able to co-aggregate with many other bacterial species (acts as attachment point)
37
Q

What is the shape, environment preference, metabolism and location of the Treponema species?
What are TWO examples of Treponema?

A
  • Spirochaete
  • Anaerobic
  • Both amino acids and carbohydrates
  • Found subgingivally
  • T. denticola (red complex), T. pallidum (syphillus)
38
Q

What THREE types of bacteria are found on the skin and therefore on the lips too?

A
  • Staphylococci
  • Corynbacterium
  • Propionibacterium
39
Q

Strep is the most dominant bacteria in the oral cavity. Which strep is most predominant?

A

S. mitis

40
Q

What bacteria is found commonly on the tongue? (answer is not simply anaerobic bacteria)

A

Stomatococcus mucilagenosus

41
Q

What are the FIVE locations of plaque on teeth? (and therefore five different types of plaque)

A
  • Smooth surface
  • Interproximal
  • Fissure
  • Supragingival
  • Subgingival
42
Q

What are black pigmented anaerobes usually associated with?

A

Periodontitis

43
Q

For Streptococcus Mutans, define the bacterial nomenclature.

A
  1. Streptococcus is the genera (type of bacterium)

2. Mutans is the individual species (of the genera)

44
Q

What TWO genera are most commonly found in plaque?

A

Streptococcus and Actinomyces (both gram +ve)

45
Q

What species of strep is most commonly found in fissure plaque?

A

S. mutans (not S. mitis, so S. mutans highly implicated in fissure caries)

46
Q

How does the plaque bacterial composition change from fissure plaque to interproximal plaque?
Which is more dominant: S. mutans or S. mitis?

A
  • More Actinomyces and obligate anaerobes

- S. mitis is more dominant

47
Q

Which area has the greatest bacterial diversity: fissure, interproximal or gingival sulcus?

A

Gingival sulcus

48
Q

What are FIVE ways that biofilm is protective for bacteria?

A
  • Protection from host defences
  • Protection from dessication
  • Protection from flowing system (rinsing action of saliva)
  • Protection against antimicrobials (one species can produce beta lactamase for the whole colony)
  • Novel gene expression and phenotype (in slow nutrient stream environment)
49
Q

What do touch sensors in bacterial cells do? Give TWO examples.

A

When attached to a surface, they trigger induction of specific genes.

  • Pseudomonas auruginosa (release EPS)
  • S. mutans (lactate production and increased growth rate)
50
Q

What are TWO mechanisms that trigger bacterial induction of specific genes?

A
  • Quorum sensing

- Touch sensors

51
Q

What is the doubling/growth rate of immature plaque vs. mature plaque?

A

<60mins (immature - few numbers, lots of nutrients)

13-15 hrs (mature)

52
Q

What is confluent growth? (bacteria)

A

Growth between individual colonies that is so close that they cannot be separated from one another.

53
Q

Describe the general bacterial composition of the THREE stages of maturing plaque?

A
  1. Early colonisers
    - Mainly cocci (S. oralis/sanguis/gordonii/mitis)
    - Some rods (A. naeslundii)
  2. Transition
    - F. nucleatum (has transitional metabolism)
  3. Late colonisers
    - Less cocci, more anaerobic rods and filaments (Red complex, Eubacterium spp.)

BONUS: Detachment stage (due to lack of nutrients in current environment)

54
Q

What specific mechanism do bacteria use to attach to biological surfaces?

A

Bacteria have specific adhesins that attach to specific receptors (e.g. antigen I/II [adhesin] attaches to salivary agglutinin [receptor])

55
Q

What are cryptitopes?

A

Hidden receptors on bacterial cells that only become active after certain conditions fulfilled.

  • Potentially explained as host promotion of binding specific microbes
    e. g. A. naeslundii only binds to surface bound proline rich proteins
56
Q

What is one special mechanism that P. gingivalis uses to aid its attachment?

A

P. gingivalis can bind to trypsin-treated epithelial cells, so it releases it’s own trypsin-like enzyme to prime the site for adhesion.

57
Q

What are the TWO types of EPS and what enzyme produces them?

What bacterial species increases this enzyme activity?

A
  • Water soluble (not stick, a1-6 linkage) and water insoluble (sticky, a1-3/4 linkage), both allow formation of water channels in plaque/biofilm
  • Glucosyltransferases (GTF) are still active outside the bacterial cell and polymerise sugars together to form EPS
  • S. mutans increases GTF activity 7-fold.
58
Q

What are THREE beneficial metabolic effects that bacteria can have for other bacteria in the biofilm?

A
  • Enzyme complementation
  • Food web (bacteria feed on waste products of others)
  • Co-aggregation
59
Q

What are THREE examples where bacterial metabolism work synergistically?

A
  • Neuraminidase (remove sialic acid cap)
  • Breakdown protein core (F. nucleatum)
  • Lactate consumption, byproduct of S. mutans = foodweb (Veillonella)
60
Q

What are the FIVE Koch’s postulates modified for plaque derived diseases?

A
  • Microbe should be present in sufficient numbers to cause disease
  • Microbe should produce increased levels of specific antibodies
  • Microbe should possess relevant virulence factors
  • Microbe should produce disease in an appropriate animal model
  • Removal of microbe should result in clinical improvement

BDS3 (22 decks)

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