Gut microflora & disease

Question 1

what diseases can be caused by a build up on dental plaque

Answer 1

Dental plaque inflammation leads to gingivitis and periodontal disease
Gingivitis - healthy gumline to inflammed, causing bleeding
Periodontitis - when gingivitis runs out of control, severe gum attack and erosion, causes teeth to fall out

Question 2

oral health is an equilibrium between ….

Answer 2

between endogenous bacteria and the oral defense system

Question 3

what oral bacteria are acquired in the hours after birth

Answer 3

Streptococcus spp. e.g. S. salivarius

Question 4

what does acquisition of oral flora depend on after birth

Answer 4

Acquisition of oral flora depends upon exposure at the time of birth, cesarean or vaginal. Shortly thereafter, breastfeeding and environmental factors.

Question 5

what oral flora are acquired in the first year of a babies life

Answer 5

streptococci, staphylococci, lactobacilli, Neisseria, Veillonella, Actinomyces, Fusobacterium spp.

Question 6

what bacteria colonise the teeth and gingiva when teeth appear in the first year

Answer 6

Streptocococcus mutans and Streptococcus sanguis

Question 7

what are the main stages/changes in oral flora in later life

Answer 7

• After tooth eruption: organisms favouring hard tissue e.g. Strep. sanguis and Strep. mutans, Actinomyces spp.
• Colonisation of crevicular tissues: anaerobic organisms e.g. Prevotella spp.
• Loss of teeth: “a 2nd childhood microflora” – alterations in flora
• Prosthetic appliance: e.g. dentures - similar to enamel plaque, may harbor large numbers of yeast

Question 8

how many species can be isolated from dental plaque

Answer 8

> 300

Question 9

how many bacteria are shed in saliva per day

Answer 9

10^8 bacteria/day

Question 10

what are two important dental diseases

Answer 10

• Caries: associated with high sugar diet and poor hygiene, Holes in teeth, malodour etc
• Periodontal diseases
1. non-destructive Gingivitis: poor hygiene, Inflamed, bleeding gums
2. destructive Periodontitis: usually as get older unless very poor dental hygiene, Gum and bone loss

Question 11

what are the virulence factors produced by streptococci in carious plaque

Answer 11

• Saccharolytic – metabolise sugars
• Glucosyltransferases – EPS glucan, mutan (insol) – plaque biofilm
• Fructosyltransferases – EPS fructan, inulin (insol) – plaque biofilm
• Acidogenic – fermentation sugars to acid (to lactic, acetic, formic acids - lower pH
• Aciduric – metabolise and grow at low pH
(low pH decalcifies hydroxyapatite enamel)

Question 12

what gram negative bacteria is thought to help slow development of dental caries

Answer 12

Veillonella - converts lactic acid of other species to less acidic products

Question 13

whta two bacteria are microbial indicators of a disease state when found in increased numbers in plaque

Answer 13

Lactobacillus and S. mutans

Question 14

what bacteria causes acute necrotising ulcerative gingivitis

Answer 14

anaerobic Prevotella intermedia, Fusobacterium, Treponema and Borrelia spp.

Question 15

what are the big 3 bacteria that cause periodontitis

Answer 15

Treponema denticola
Porphyromonas gingivalis
Aggregatibacter actinomycetemcomitans

Question 16

what two bacteria make up the corn cobs found in the famous photo of dental plaque

Answer 16

Bacterionema matruchotii and Streptococcus sanguis - Streptococci produce lactic acid and Bacterionema converts it to butyric acid as its food source (rudimentary food chain)

Question 17

what is the acquired pellicle

Answer 17

a protein film that forms by selective binding of glycoproteins from saliva that prevents continuous deposition of salivary calcium phosphate. It forms in seconds after a tooth is cleaned, or after chewing.

Question 18

what signalling molecules do gram +ve oral bacteria use for intraspecies communication

Answer 18

competence stimulating peptides, which help promote single-species biofilm formation. (quorum sensing)

Question 19

what cell-cell signalling molecule mediates interspecies quorum sensing to stimulate plaque formation

Answer 19

4, 5-dihydroxy-2, 3-pentanedione (DPD), also called Autoinducer-2 (Al-2)

Question 20

what are the pioneer species of plaque

Answer 20

streptococci

Question 21

if you cant prevent biofilm formation what antipathogen strategies can be used prevent periodontal pathogens joining the biofilm

Answer 21

attachment blockers and detachment signals

Question 22

what type of tehcnique was used in the human microbiome project and what did they test

Answer 22

• Use molecular metagenomic techniques

* Testing nasal, oral, skin, gastrointestinal and urogenital colonies

Question 23

what morphological characteristics does helicobacter pylori have

Answer 23

Spiral helical shape with lots of flagella on one end.

Question 24

what diseases does helicobacter pylori cause and how

Answer 24

penetrates mucin lining and produces urease to neutralise acid pH. Causes stomach ulcers and stomach cancer.

Question 25

how does helicobacter pylori surviv in the strongly acidic stomach and immune system

Answer 25

by excreting urease, neutralize the acidic environment by converting urea to basic ammonia and buffer bicarbonate
Invade protective inner lining of the stomach so can be protected from immune system

Question 26

how is H pylori able to sense acid pH

Answer 26

TlpA and TlpD are each independent acid sensors, swim away.

TlpD also mediates attraction to basic pH.

Question 27

give examples of waterborne GI pathogens

Answer 27

Salmonella typhi - Typhoid

Vibrio cholerae - Cholera

Question 28

give examples of foodborne GI pathogens and the foods they are found in

Answer 28

Campylobacter jejuni – chicken, salads
Salmonella enterica serovars, Typhimurium, Enteriditis – chicken, eggs
STEC e.g. E. coli O157 – beef, lamb, salads
Listeria monocytogenes – pate, fish
Yersinia enterocolitica - pork

Question 29

what are serovars/serotype

Answer 29

a distinct variation within a species of bacteria or virus or among immune cells of different individuals - share distinctive surface structures.

Question 30

what are feacal transplants and what are they largely used for

Answer 30

the transfer of stool from a healthy donor into the gastrointestinal tract for the purpose of treating recurrent C. difficile colitis.

Question 31

how do gut flora prevent dysbiosis

Answer 31

flora prevents harmful species colonizing through competitive exclusion, the “barrier effect”:
helpful gut flora species adhere to the mucosal lining of the intestine and block access for pathogens
produce bacteriocins

Question 32

what causes pseudomembranous colitis

Answer 32

the overgrowth of opportunistic Clostridium difficile

Question 33

what facultative bacterial species make up normal healthy microflora

Answer 33

streptococci, lactobacilli, staphylococci, corynebacterial

Question 34

what early microflora initially colonise the gut in large numbers

Answer 34

E. coli and streptococci.

Question 35

what bacteria dominate breast fed babies gut and why

Answer 35

by bifidobacteria, possibly presence of bifidobacterial growth factors in breast milk.

Question 36

what fungi are found in the mature gut microbiome

Answer 36

Candida, Saccharomyces, Aspergillus, Penicillium.

Question 37

what bacterial species are present in the mature gut microbiome

Answer 37

• Clostridium, Fusobacterium, Eubacterium, Ruminococcus, Peptococcus, Peptostreptococcus, and Bifidobacterium
• Escherichia and Lactobacillus present to a lesser extent

Question 38

what are the symbiotic benefits of gut microflora

Answer 38

• ferment unused energy substrates
• train the immune system
• prevent growth of harmful, pathogenic bacteria
• regulate the development of the gut
• produce vitamins for the host (e.g. biotin and vitamin K)
• produce hormones to direct the host to store fats.

Question 39

what species shift occurs at the weaning stage to determine lifelong gut microflora

Answer 39

shift at weaning from predominantly facultative anaerobic species, such as streptococci and E. coli, to mostly obligate anaerobic species

Question 40

how does the intestine discriminate between pathogenic and commensal bacteria

Answer 40

Pattern recognition receptors (tolerance to helpful species built up in infancy): they include TLRs and NOD/CARD

Question 41

what are Nucleotide-binding oligomerization domain/caspase recruitment domain isoforms (NOD/CARD

Answer 41

cytoplasmic proteins that recognize endogenous or microbial molecules or stress responses and forms oligomers that activate inflammatory caspases.

Question 42

what is NF-κB

Answer 42

NF-κB is a protein complex that controls transcription of DNA, cytokine production and cell survival (induces production of inflammatory molecules)

Question 43

what bacteria has PSA and what is unique about them

Answer 43

B. fragilis . • 2 of these 8 capsular polysaccharides have a unique zwitterionic structure (positive and negative charges on each repeating unit);

Question 44

what intrinsic feature of a healthy immune system is completely controlled by a single bacterial molecule

Answer 44

Purified Polysaccharide A was able to restore Th1/Th2 balance to the entire organism.
( PSA restored IFNγ levels to normal and reduced Th2 cytokines. )

Question 45

PSA stimulates ____ and suppresses ____.

Answer 45

stimulates IL-10 and suppresses IL-17

(IL-10 activates t regulatory cells and dampens inflammation by inhibiting the synthesis of pro-inflammatory cytokines)
(Th17 cells produce IL-17, potent inflammatory T-cell cytokine associated with every known autoimmune disease. )

Question 46

how deos PSA protect the intestines from immune attack

Answer 46

producing cytokine IL-10 to suppress the pro-inflammatory IL-17 and protect the intestines