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GI Week 1 > Microbiology of the Upper GI Tract > Flashcards

Microbiology of the Upper GI Tract Flashcards

1
Q

What are the general GI system defenses against infection?

A 
epithelium barrier
mucus barrier
peristalsis to clear things
saliva with lysozyme, IgA, etc
normal flora 
acidity
peyer's patches in intestine
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2
Q

True or false: normal flora begins to develop in our mouths during our first week of life?

A

false - babies have clean mouths until teeth erupt

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3
Q

True or false: the upper GI tract contains a huge amount of normal flora compared to elsewhere in the gut?

A

false - actually relatively few compared to the mouth and large intestine

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4
Q

What are the four phyla that can be found in the normal biota of the stomach

A

proteobacteria
firmicutes
actinobacteria
bacteroidetes

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5
Q

What are the general classes of bacteria seen in microbiome of the large intestine?

A

anaerobes
gram negative rods
enterococcus
spirochetes

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6
Q

What do we call an infectious disease that causes tooth decay?

A

a dental cary

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7
Q

What are the risk factors for dental caries?

A

high-sugar diet, poor oral hygriene, reduced amount of saliva, smoking, periodontal disease

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8
Q

What percentage of adults have had at least 1 tooth filled?

A

80%

highest incidence in AI/AN children

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9
Q

What’s the mechanism for how the bacteria cause tooth decay? It;s not that the bacteria are “eating” the teeth….

A

When you eat fermentable sugars, acid-producing bacteria use them for energy and release acid as a byproduct

this decreases the pH of the mouth and leads to demineralization of teeth

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10
Q

What’s the treatment for dental caries and why do we take this so seriously?

A

you drill out the decayed area and put in a filling. We do this because if you don’t, the enamel can completely wear away and then you give the bacterial access to the blood supply underneath

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11
Q

What is periodontal disease?

A

an infectious disease destroying the supporting structures of the teeth.

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12
Q

What’s the mild form of periodontal disease?

A

gingivitis - only affects the gums with irritation, redness and swelling

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13
Q

What’s the more severe form of periodontal disease?

A

periodontitis, which is infection of underlying tissues and bones

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14
Q

What are some conditions that periodontitis may be associated with?

A 
heart attack
stroke
lung disease
premature birth
DIABETES
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15
Q

How is the damage in peridontal disease mostly mediated?

A

via the host immune response to the infection

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16
Q

While gingivitis is just swelling and redness of the gums, what will you see grossly in periodontitis?

A

the gums recede and you have localized loss of attachment of the teeth to the gums

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17
Q

What virulence factor is essential for virtually all dental infectious diseases?

A

biofilm prroduction

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18
Q

What are biofilms composed of?

A

two or more bacterial microcolonies that are enclosed in glycocalyx (composed of polysaccharides)

also some proteins and DNA

note - there can be hundreds of species in a biofilm

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19
Q

Describe the process for formaiton of a biofilm.

A
  1. bacterial weakly adhere to the surface cells
  2. stronger adhereance over time - likely co-adhesion mediated
  3. multiplation of bacteria
  4. bacterial make polysaccharide
  5. polysaccharide builds up and the microbial composition changes over time as it makes it mroe suitable for organisms that otherwise wouldn’t survive
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20
Q

What are some of the reasons why bacteria would want to live in a biofilm?

A 
easier to adhere
protects them from the immun system
protects them from ABx
allows for symbiotic relationships
local conditions of pH are more hospitable than the actual environment
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21
Q

Is plaque always bad? It’s basically a biofilm….

A

Plaque can be stable with no infectious microorgnisms, but it’s easy for perturbations to change the microbial balance toward more virulent orgnaisms

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22
Q

What general type of organisms predominate in the oral cavity (we each cary about 100-200!)

A

anerobic organisms predominate

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23
Q

What are some species of streptococci that play important roles in protecting against dental caries and periodontiis? How?

A

the “mitis” group = S sanguinis, S oralis, S gordonii and S. mitis

they produce hydrogen peroxide which inhibits the growth of other oral bacteria

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24
Q

Where are the microbes that cause caries usually located?

A

plaques on tooth surfaces especially in crevices and between teeth

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25
Are the species that cause caries usually gram negative or positive?
gram positive
26
Microbes that cause periodontal disease are located where?
below the gumline int he subgingival space
27
Are microbes that cause periodontal disease usually gram negative or positive?
gram negative
28
Why is it hard to identify specifically which "bad" oral microorgnisms are th ekey players in someone's disease?
because they're almost all streptococci and will look the same on growth and 16s rRNA analysis also all strep viridans
29
What group is particularly associated with tooth decay?
mutans group - | strep mutans and strep sobrinus
30
What virulence factor for the mutans group make it likely to cause caries?
adhesin-like surface-associated proteins like the AgI and AgII family that are capable of binding to receptors in the pellicle also extracellular glucosyltransferases Gtfs that are capable of synthesizing glucans - a type of polysaccharide from istu to make more S mutans binding sites
31
What is a keystone pathogen?
It's an organism that can be present without causing disease until it reaches a certain ratio, after which is can orchestrate destructive inflammation and remodling of the normally symbiotic microbiota into a dysbiotic state mess with complement basically
32
What are three examples of keystone pathogens involved in dental caries?
treponema denticola tannerella forsythia porphyromonas gingivalis (most studied bc it can be cultured)
33
what orgnaism is particularly related to the SEVERITY of periodontal disease?
aggregatibacter actinomycetemcomitans
34
What are some ways to prevent dental caries and periodontal disease?
less sugar in diet brush and floss regularly fluoride increase saliva flow
35
How does fluoride work?
it promotes remineralizaiton to counterract the effects of demineralization under low pH conditions Inhibits bacterial glycolysis and pH maintenance enzymes
36
Which level of periodontal disease is reversible?
gingivitis is generally reversible with good oral care
37
What are some of the treatment options for mild cases of periodonititis?
scaling to remove tartar and bacteria root planing to discourage further growth antibiotics - topiccal is typical but use oral if persistent
38
What antibiotics are usually used for periodontitis?
amoxicillin and metronidazole
39
What are some treatments for severe cases of periodontitis?
surgical treatments to fix permanent damage: flap surgery, soft tissue grafts, bone grafts
40
Oral thrush is most common in what groups?
babies elderly immunocompromised
41
What people get hairy leukoplaki?
HIV positive individuals with EBV infection
42
What serious skin infection can occur from untreated dental infections spreading into the nearby tissue?
Ludwig's angina
43
What are the symptoms of ludwig's angina?
``` breathing difficulty confusion or other mental changes fever neck pain neck welling erythema weakness, fatigue ```
44
Where can candidiasis occur?
usually on the tongue or inner cheeks sometimes spreads to roof of mouth, bums, tonsils or pharynx can reach esophagus, which is dangerous
45
You can diagnose thrush entirely on signs and symptom, but scrapings would show what?
hyphae with spores at the edn
46
How do you treat thrush?
1. usually topical treament with clotrimazole or nystatin 2. unresponsive cases with systemic antifugal such as fluconazole 3. worse case scenario with IV amphotericin B
47
How is H pylori transmitted?
fecal oral transmission
48
How many adults are infected with H pylori?
50% in the US | virtually everyone in the third world
49
H pylor gram positive or negative?
gram negative
50
H pylori morphology?
flagellated helix-shaped rod (spirilli)
51
H pylori relation to O2 use?
microaerophilic - can only survive in a little O2 makes it hard to culture
52
H pylor urease positive or negative
urease positive
53
What is the lifetime risk for ulcer disease in those with H pylor infections? Gastric cancer?
only 10-20% for peptic ulcer disease 1-2% for distal gastric cancer
54
Why is there is range in presentations?
there are lots of different strains that can be more or less virulent individual host responses differ gastric microbiome differs and plays a role
55
What are essentially the two non-cancer issues h pylori can cause?
symptoamtic gastritis | ulcers
56
what are the two general cancers H pylori an trigger?
carcinoma | lymphoma
57
What is gastritis?
inflammation fo the gastric mucosa - can be transient or chronic
58
What are the symptoms of gastritis?
gnawing or burning ache in upper abdomen (may be worse or better with eating nausea vomiting feeling of fullness in upper abdomen after eating
59
What are the symptoms of gastric ulcers?
burning abdominal pain almost anywhere, worse when stomach empty - flares at night - temporarily relieved by eating foods and can disappear and then return for a few days or weeks can also vomit blood, bloody stools, nausea, vomiting, weight loss, appetite changes
60
What are some of the ways that H pylori survives in the stomach?
inhibits phagocytosis inhibits the adaptive immune response evades killing by ROS and NO evades recognition by PAMPs Urease activity raises local pH so it doesn't have to live at pH 2 (since it can't)
61
How does urease increase local pH?
It breaks down urea into CO2 and ammonia, which is basic
62
Where in the stomach does the H pylori like to live and why?
along the epithelium because the pH is about 6 there, which is can withstand it just has to make it there through the more acidic lumen using the urease buffering
63
How does it manage to get thorugh the pH = 2 layer so quickly?
It has an excellent flagella-based motility system
64
How does it know where to go?
It has a chemotaxis system based on pH gradient - helps them know which direction to go to get to the epithelium and pH of 6
65
What will the H pylori do once they reach the epithelium?
they adhere to the epithelium toa void mechanical clearance this promotes invasion and persistence the adhesins contribute to the inflammation
66
What are the two best characterized specific virulence factors of H pylori?
VacA and CagA
67
What is VacA?
It' a pore-forming cytotoxin that allows leakage of Ca+ from epithelial cells
68
What is CagA?
it travels through a type 4 secreiton system into the host cytosol and affects the proliferative activities, adhesion and cytoskeletal organization of epithelial cells whole system is highly proinflammatory
69
How does H pylori cause ulcers?
basically, we cause the ulcer 1. they attach to the epithelium and trigger inflammation 2. our inflammatory cells are indescriminant and kill our own epithelium, forming an ulcer
70
What are the 4 types of diagnostic tests for htis?
encoscopy with culture breath test stool test blood test
71
A week of "triple therapy" is currently used. What does this entail?
2 antiibotics (clarithromycin and amoxicillin) and a PPi to aid in the healing of the ulcer
72
What are the consideratios for endoscopy and culture for diagnosis?
it's a gold standard test because you can actually see the uclers, but it's hugely invasive and way expensive
73
What's a test we can do on culture after endoscopy to check for H pylori?
the rapid urease test, which detects the actual enzyme urease
74
How does the breath test work for H pylori?
it detects radioactive CO2 that's formed thorugh the urease reaction
75
Can the breath test diagnose? check for cure? What's the issue?
It's good for both diagnosis and confirming cure, but it require sa skilled technician - easy to screw up
76
What is being detected by the blood test for H pylori? What does this mean for utility?
it detects antibodies against H pylori | means it's useful for initial diagnosis only and can't confirm a cure
77
What's being detected by the stool test for H pylori? What does this mean for it's utility?
looks for H pylori antigen this means it's good for both diagnosis and confirming cure
78
If you had to pick wuich cancer to get from H pylori, which would you pick?
gastric MALT over carcinoma
79
Describe gastric MALT
it's mucosa-associated lymphoid tissue lymphoma in the stomach due to long term inflammation basically a tumor of B cells - get indigestion, heartburn and abdominal pain
80
H pylori is a risk factor in what percentage of gastric carcinoma?
65-80%

GI Week 1 (13 decks)

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