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ACVIM Specialty 2023 > GI: microbiome and enteral nutrition > Flashcards

GI: microbiome and enteral nutrition Flashcards

1
Q

Name 4 of the major bacteria phyla identified in the healthy gut of dogs and cats

A

Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, and Actinobacteria

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2
Q

One of the major metabolic functions of the GI microbiome is to ferment non-digestible dietary residues into volatile fatty acids. Name the short chain volatile fatty acids

A

Acetate, propionate, butyrate

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3
Q

What short chain fatty acid is the major energy source for colonocytes?

A

Butyrate

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4
Q

Name 3 vitamins synthesized by the microbiome

A

Biotin, folate, vitamin K

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5
Q

Name 3 minerals that the microbiome assists in the absorption of

A

Calcium, magnesium, iron

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6
Q

Name 2 ways that the microbiome contributes to host mucosal immunity

A

1) Colonization by bacteria after birth influences T cell repertoires and Th1/Th2 cytokine profiles
2) Form a biofilm to prevent pathogenic bacterial colonization - displacement, competition for nutrients, production of antimicrobial substances (lactic acid, bacteriocins)

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7
Q

Surface enterocytes sense danger signals within the intestinal lumen and respond by secreting what products?

A

Defensins, IgA, chemokines and cytokines

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8
Q

What are M cells?

A

Specialized epithelial cells that overlie lymphoid follicles. Sample luminal antigens and deliver them to DCs for antigen presentation

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9
Q

What are two pattern recognition receptor (PRR) systems used by the mucosal immune system to recognize pathogens? Where are they located?

A

Toll like receptors (TLRs) - transmembrane
Nucleotide-binding oligomerization domain (NOD1 and NOD2) - intracellular

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10
Q

Immune responses to commensal bacteria in IBD may be driven by what TLR/antigen?

A

Flagellin activating TLR5

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11
Q

Increased numbers of intestinal bacteria can cause malabsorption and diarrhea through what mechanisms?

A

1) Competition for nutrients - such as bacterial binding of cobalamin, which prevents absorption
2) Metabolism of nutrients into products that promote colonic secretion/diarrhea
3) Biochemical injury to the brush border, decreasing enzyme activity

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12
Q

Selective IgA deficiency leading to bacterial overgrowth occurs in what breed?

A

German Shepherds

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13
Q

What is the difference between microbiota and microbiome?

A

Microbiota = taxonomy (who is there)
Microbiome = the gene content and function (what are they doing)

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14
Q

Why is bacterial culture less useful for evaluating the microbiome?

A

Majority of bacteria (especially in the colon) are anaerobes; a reduction in beneficial bacteria is often more relevant than overgrowth of one species - difficult to identify on culture

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15
Q

What is DNA shotgun sequencing or metagenomics?

A

A technique that aims to sequence extracted DNA in a sample without prior PCR amplification on a high throughout sequencer - allows assessment of taxonomy and functional gene categories

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16
Q

What are 3 advantages of DNA shotgun sequencing over 16S RNA sequencing?

A
  • Better resolution at the bacterial species and strain level
  • Can identify archaea, fungi, and DNA viruses
  • Can provide more detailed info on virulence genes and antimicrobial resistance genes
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17
Q

What are disadvantages of DNA shotgun sequencing over 16S RNA sequencing?

A

High cost, advanced bioinformatics needed to assemble the data

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18
Q

What is the 16S rRNA gene?

A

Several bacteria variable gene regions that are flanked by conserved regions

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19
Q

What is 16S rRNA gene sequencing?

A

DNA is extracted from a sample, and bacterial universal primers are used to amplify the conserved regions consisting of the 16S gene. PCR amplicons are sequenced using a high throughput sequencer

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20
Q

What is alpha diversity?

A

The richness and diversity of a sample - how many taxa are in one sample

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21
Q

What is beta diversity?

A

How similar one sample is to another sample based on the taxa present

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22
Q

What are the advantages of 16S rRNA gene sequencing?

A
  • Useful to detect overall differences in microbiota composition between groups; cannot detect the exact bacterial species (semi-quantitative)
  • Relatively inexpensive
23
Q

What are the disadvantages of 16S rRNA gene sequencing?

A
  • Changes in taxonomic databases and bioinformatics pipelines over time make comparing results across studies difficult
  • Some taxa will differ significantly depending on the extraction/amplification technique used
  • Gives you relative abundance of bacteria (not exact quantities)
24
Q

What method does the dysbiosis index use?

A

Quantitative PCR for specific taxa that have been identified as clinically relevant based on prior sequencing studies

25
Q

What percent of dogs and cats with chronic enteropathies have decreased abundance of C. hirononis?

A

50-60% of dogs, 30% of cats

26
Q

In one study, cats with small cell intestinal lymphoma had increased numbers of what bacteria attached to the mucosa in the ileum and colon compared to cats with IBD?

A

Fusobacterium sp.

27
Q

What is metabolomics?

A

Analysis of microbial-derived metabolites (SCFA, fecal bile acids, etc)

28
Q

Tryptophan is converted by bacteria into indole metabolites. What are their function in the GI tract?

A

Indoles can be anti-inflammatory (decrease IL-8 expression), induce mucin gene expression, and strengthen tight junctions

29
Q

Fecal concentrations of what short chain fatty acids were lower in dogs with chronic enteropathy than healthy controls?

A

Acetate and propionate

30
Q

What does richness refer to?

A

The overall number of unique operational taxonomic units (proxy for species) in a sample

31
Q

What does diversity refer to?

A

A measure of the variability of the microbiome, considering both the richness (number of unique species) and relative abundance of those species

32
Q

Puppies up to 5 to 6 weeks of age had what changes in their microbiome compared to older dogs?

A

Increased dysbiosis index, increased C. difficile, decreased C. hiranonis and secondary bile acids

33
Q

Administration of metronidazole for 14 days caused what changes to the microbiome in dogs? How long did it take for those changes to reverse?

A

Decreased richness, decreased Fusobacterium, increased dysbiosis index, increased fecal lactate and decreased secondary bile acids. Took 4 weeks to recover

34
Q

In a study of dogs with steroid responsive CE, how much lower were secondary fecal bile acids in affected dogs compared to control dogs? How did steroids affect it?

A

29% vs 88%; improved to 94% with steroid treatment

35
Q

In a study of dogs with steroid responsive CE, did the dogs’ dysbiosis index improve with steroid treatment?

A

No - remained increased despite clinical resolution of disease. C hiranonis did improve though

36
Q

In a study of 773 shelter dogs, administration of a synbiotic reduced the occurrence of diarrhea in the first 14 days by what percent?

A

From 27% in the control group to 18% in the synbiotic group

37
Q

In a study of 773 shelter dogs, administration of a synbiotic reduced the occurrence of >2 consecutive days of diarrhea by what percent?

A

8% in the control, 4.6% in the synbiotic group

38
Q

In healthy cats given clindamycin, concurrent administration of a synbiotic had what beneficial effects?

A

Administration of synbiotics decreased hyporexia and vomiting

39
Q

For puppies with Parvovirus, administration of an FMT improved what measures of disease?

A

Faster resolution of diarrhea, shorter hospitalization (3 days vs 6 days), decreased mortality (21% vs 36%)

40
Q

What effects did tylosin (administered for 7 days) have on the microbiome?

A

Decreased bacterial diversity (some resolved, some didn’t), increase in primary bile acids (lasted until day 63)

41
Q

What enzymatic process is required to convert primary to secondary bile acids?

A

7-alpha-dehydroxylation

42
Q

In healthy research dogs given enrofloxacin and metronidazole, what effect did giving a synbiotic have?

A

Reduced hyporexia, no difference in vomiting or diarrhea

43
Q

Based on multiple cross over studies, how long do the effects of synbiotics last?

A

At least 8-9 weeks (affected second study period too)

44
Q

Administration of Fortiflora to healthy dogs had what effect on cobalamin and folate?

A

Decrease in cobalamin with moderate hypocobalaminemia developing in 40%. No effect on folate

45
Q

When given to puppies for one year, Enterococcus faecium (Fortiflora), induced what changes?

A

Increased fecal and serum IgA levels, increased vaccine associated IgA and IgG levels

46
Q

Name the primary bile acids. What are they conjugated to?

A

Cholic acid, chenodeoxycholic acid - synthesized in the liver from cholesterol and conjugated to taurine or glycine

47
Q

Name the secondary bile acids

A

Deoxycholic acid, lithocholic acid

48
Q

What bacteria has been associated with AHDS?

A

Toxin-producing C. perfringens (potentially the netF toxin gene)

49
Q

Helicobacter species produce what enzyme that is used to buffer gastric acid?

A

Urease - converts urea to ammonia

50
Q

How does omeprazole administration change the gastric microbiota?

A

Decreases Helicobacter (from 98% of gastric bacteria to 92%), allowing for growth of Firmicutes/Fusobacteria. Increases total number of bacteria in the duodenum

51
Q

In patients with an esophagojejunal feeding tube placed fluoroscopically with wire guidance, post pyloric access was gained in what percent of cases? What was the mean duration of the procedure?

A

95%
63 minutes

52
Q

Dogs and cats receiving corticosteroids when a PEG tube is placed had what percent complication rate compared to controls?

A

43% vs 18% - included infection of the site, PEG tube dislodgment, and chewing of the tube around the stoma

53
Q

In a retrospective study evaluating E tube complications in 123 patients, what percent experienced a complication related to tube placement?

A

44% (same in dogs and cats)
- 14-17% infection at the E tube site (mostly Enterococcus and E coli)
- Regurgitation of food through the stoma noted in 7 dogs and 1 cat
- 10-13% required re-suturing due to loose sutures
- 5-6% dislodgment

54
Q

In a retrospective study evaluating E tube complications in 248 cats, what percent of cats had complications and what were they?

A

35.8% complication rate
- Tube dislodgment 14%
- Stoma site infections 12% - increased risk while on glucocorticoids or oncolytic agents

ACVIM Specialty 2023 (38 decks)

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