Lecture 6

Question 1

Gnotobiotic

Answer 1

Study of animals living in a micro biologically defined environment, either germ free or colonized with known bacteria

Question 2

Microbiota

Answer 2

The sum of all microorganisms (including bacteria,archaea, eukaryotes and viruses) that reside in and/or on a host or specified part of host

Ex: GI tract

Question 3

What microbiota is the densest and most diverse in the gut, and in whole human body?

Answer 3

Colonic microbiota

Question 4

The human body consist of?

Answer 4

Archaea, bacteria, virus, and eukaryotes.

Question 5

Differences in fecal microbial community diversity composition and function have also been correlated with?

Answer 5

Crohn’s disease 
Ulcerative colitis
Irritable bowel syndrome (IBS)
C. Difficile-associated disease
Acute diarrhea

Question 6

Describe clostridium difficile

Answer 6

Gram positive
Anaerobic
Rod-shaped
Motile bacterium

Question 7

C. Difficile spreads in what types of way and is notable for producing?

Answer 7

C. Difficile is a spore former

Notable for its ability to produce exotoxins

Question 8

CDIs cause what

Answer 8

C. difficile infection case a spectrum of disease which range from mild diarrhea to pseudomembranous colitis

Question 9

What type of pathogen is C. Difficile

Answer 9

An opportunistic pathogen

Question 10

Where can C. Difficile colonize

Answer 10

Large intestine of human, domestic, and wild animals

Question 11

What protects the large intestine from invasive pathogens and how does it do it?

Answer 11

It is protected by indigenous flora (fecal microbiome)

Microbes provide colonization resistance against pathogenic species through competition of nutrients and attachment sites of gut wall

Question 12

What provides a niche for colonization. By intestinal pathogens?

Answer 12

Antibiotics provide a niche for intestinal pathogens because it disrupts the barrier of micro flora and diminish colonization resistance.

Question 13

Reduction of these two phyla by antibiotics are important to the pathophysiology of C. Difficile

Answer 13

Bacteroides and Firmicutes

Question 14

C. Difficile was identified as what in patient stool? What was the name of the disorder? What was this disorder associated with?

Answer 14

It was identified as cytoxin. With patients that where identified with the disorder pseudomembranous colitis. Which is frequently associated with anti-microbial use.

Question 15

Clostridium difficile is acquired through?

Answer 15

The Ingestion of spores

Question 16

Once C.difficile is acquired where does it go?

Answer 16

Once acquired spores resist acidity of stomach and germinate into the vegetative form in small intestine

Question 17

Disruption of normal gut flora, typically by antimicrobial allows?

Answer 17

It allows C. Difficile to proliferate causing a broad spectrum of clinical manifestations.

Diarrhea, fulminant colitis, death

Question 18

What is used to subset the colonization of C. Difficile

Answer 18

Antibiotics

Question 19

People can be colonized with a non-toxigenic strain of C. Difficile. True or False?

Answer 19

True

There are non-toxigenic strains that do not produce toxins.

Question 20

Progression to symptomatic CDI is due to?

Answer 20

Not producing a sufficient antibody response

Question 21

For the toxin to remain asymptomatic what must the body do?

Answer 21

Mount a sufficient humoral response (produce antibodies)

Question 22

Pathogenicity is dependent on these two diarrhea producing toxins?

Answer 22

Toxin A (TcdA)
Toxin B (TcdB)

Question 23

All toxigenic strains contain?

Answer 23

Toxin B (TcdB)

Question 24

Several interventions targeting the intestinal microbiota have been used to maintain and improve host health. These include:

Answer 24

Probiotics
Prebiotics
Fecal transplant
Immune modulators 
Phage therapy
Antibiotics

Question 25

Probiotics

Answer 25

Live organisms that confer a health benefit to the host when administered in adequate amounts

Question 26

Prebiotics

Answer 26

Nondigestable food components that are selectively fermented by good gut microbial community

Question 27

Fecal transplantation

Answer 27

Fecal transplant from healthy donor can restore a dysbiotic community through the administration of complete, complex microbiota in the form of feces

Question 28

Phage therapy

Answer 28

A strategy to create a beneficial shift in microbiome is to develop specific bacteriophages to target particular microbes. Lyse susceptible bacterial cells

Question 29

Antibiotics

Answer 29

Even though antibiotics can disrupt the microbiota but specific antibiotics can also be used to target dysbiosi, resulting in a beneficial clinical outcome.

Question 30

Modification of the citric acid cycle for fermenting bacteria is called

Answer 30

Reductive (incomplete) cycle

Question 31

Fermenting bacteria are not carrying out aerobic respiration so it not best to create a lot of?

Answer 31

Produce NADH and FADH2

Question 32

What reaction products are necessary precursors for biosynthesis of amino acids?

Answer 32

Oxaloacetate
Succinyl-COA
Alpha-ketoglutarate

Question 33

What is the solution to reduce use of NADH, FADH2 & not using an oxidative pathway?

Answer 33

Convert to incomplete reductive cycle

Question 34

Fermenting bacteria have no activity for this enzyme?

Answer 34

Alpha- ketoglutarate dehydrogenase

Question 35

In the reductive cycle at what part of the pathway is blocked?

Answer 35

Pathway is blocked between alpha-ketogluterate to succinyl-COAdue do to the little use of alpha-ketoglutarate dehydrogenase

Question 36

How Succinyl-COA made?

Answer 36

By reversing the reaction between oxaloacetate to succinyl-COA

Question 37

What enzyme is used to get to succinate from fumerate?

At this step what also happens?

Answer 37

Fumerate reductase

Use of FADH2