Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Block 15 > Microbiology Of The Gut > Flashcards

Microbiology Of The Gut Flashcards

1
Q

What are the mechanisms/categories of GI infection (3)?

A

Non inflammatory
Invasive/inflammatory
Penetrating

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Give an example of a virus that uses the GI tract for entry point but with no/little GI symptoms?

A

Polio virus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the mechanism of non-inflammatory GI infections?

A

Enterotoxins (may be pre-formed in food that’s ingested), mucosal adherence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the location of non-inflammatory GI infections

A

Proximal small bowel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Give examples of non-inflammatory GI infections?

A

Vibro cholerae - Cholera disease produced by cholera toxin
Bacillus cereus - emetic toxin causes vomiting, heat stable, associated with rice, long-acting toxin also produced which causes nausea and diarrhoea
Enterotoxigenic E.coli- toxin produced is similar to cholera toxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the mechanism of inflammatory GI infections?

A

Invasion of mucosa production of cytotoxinsq

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the location of inflammatory GI infections?

A

Colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Give examples of inflammatory GI infections

A

Shigella sp. - produces shigella toxin (most potent toxin known), invades GI epithelium and spreads laterally along epithelial layer (local invasion of tissue)
Salmonella sp. - invades local epithelial GI cells, which causes nausea, vomiting and diarrhoea
Campylobacter jejuni - can mimic acute appendicitis, inflammatory adenitis and can be mistaken for Crohn’s disease
Enterohaemorrhagic/Enteroinvasive E.coli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the mechanism of penetrating GI infections

A

Induced phagocytosis, invades cells of the immune system and disseminate beyond the gut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the location of GI infections?

A

Distal small colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Give examples of penetrating GI infections

A

Salmonella typhi - symptoms start 6- 30days post contact, slow onset of high grade fever, generalised weakness, cramps, disseminates into bone marrow and tissue macrophages
Yersinia enterocolitica - gastroenteritis, but can invade immune system as well
Listeria monocytogenes - disease of extremes of age (very young, old, immunocompromised), invades cells of immune system, gastroenteritis, can cause meningitis if spreads

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the sensory host defences against GI infections?

A

Smell taste

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the behavioural host defences against GI infections?

A

Pooing in the toilet, away from food - sewer system keeps sewage separate from drinking water
Washing hands after going to toilet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the physiological host defences against GI infection?

A

Gastric pH - 1.5-3.5pH, achieved mostly by HCl
Bile salts and acids - in proximal small bowel, attacks bugs which get through
gastric acid
Peristalsis - maintains movement to prevent time for microorganisms to settle on
epithelium and start an infectious process
Mucus - gut epithelia produces mucus which is a physical barrier and is full of
antimicrobials (e.g. lysozyme) - mucus can also be upregulated by signalling molecules if there is an infection to create more of a barrier to prevent more tissue damage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the immune system defences against GI infection?

A

Humoral (antibody-mediated) immunity with secretory IgA - binds to bacteria in gut
preventing them from accessing the epithelial cells (immune exclusion)
Cell-mediated immunity - involves patrolling macrophages and cell signalling
processes
GALT (gut associated lymphoid tissue) - acts as a focus for lymphocytes and
immune cells, aiding in recruitment if there is infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the normal gut flora of the GI tract defences against GI infection?

A

Colonization resistance - occupies space, produces antibiotic-like substances (bacteriocins), end products of metabolism may be toxic
Stimulate local immune system

17
Q

What is the function of microbiome?

A

Synergistic
Synthetic – forms folate, biotin, vitamin K, vitamin B
Promotes release of nutrients from foods – Fe2+, Ca2+, amino acids
Removes toxins from the breakdown of metabolism – alkaloyds, hydrogen,
heterocyclic amines from cooking
Out competes pathogens – colonisation resistance, prevents pathogen
establishment
Releases energy from carbohydrates by breaking them into sugarsk

18
Q

What infection can GI regional flora cause if it gets into the rest of the body

A

Peritonitis

Urinary tract infections

19
Q

What is the appendix?
What surround the appendix?
What are the benefits of having an appendix?

A

Vestigial remnant, but new research shows the appendix
The appendix is surrounded by lots of lymphoid tissue MALT (mucosal associated lymphoid tissue) which aids immune response to gut infection
The appendix stores a copy of your gut flora, so following an infection (e.g. cholera, C. difficile) where the diarrhoea flushes out the majority of your gut flora, the store can repopulate the gut with the healthy gut flora
Hence, patients who lack an appendix are much more prone to recurrences of C. difficile infection because it takes much longer for them to repopulate their gut flora

20
Q

What are the symptoms of bacteria overgrowth

A 
Diarrhoea
Bloating
Abdominal pain
Flatulence
Steatorrhoea – fatty stools o Weight loss
21
Q

What diseases can occur due to bacterial overgrowth?

A 
Fe deficiency – microcytic anaemia
B12/folate deficiency – macrocytic anaemia
Ca2+ deficiency – tetany
Vitamin A deficiency – visual acuity
Selenium – dermatitis
Protein – weight loss, cachexia
Fats – haemorrhagic stroke
22
Q

How is a diagnosis of bacterial overgrowth occur?

A

Hydrogen breath test

Increase in total flora (1010 organisms/ml diagnostic)

23
Q

What is the treatment of bacterial overgrowth?

A

Treat underlying condition – e.g. due to PPIs, needs to be reduced
Rifaximin

24
Q

What is bacterial overgrowth syndrome?

A 
Malabsorption (Steatorrhea, Diarrhoea)
Deficiency of fat-soluble vitamins
Macrocytic anaemia
Diagnosis
o >105 bacteria/ml in a proximal small bowel aspirate
o 14C-D-xylose breath test • Management
o Correct underlying condition
o Nutritional supplements
o Suppressive antimicrobial therapy
25
Q

What are gut flora associated diseases?

A

Autism – C. botiae
Asthma/atopy - decreased bifidobacteria, increased clostridia
Obesity – decreased bacteroides, increased actinobacteria

26
Q

Do antibiotics help with gastroenteritis?

A

Rarely help, hence rarely prescribed
Make E. coli O157 worse
Cause diarrhoea

27
Q

Is gastroenteritis contagious, what is the implication?

Where does it come from?

A

Yes-needs barrier nursing

Travel, occupation, pets

28
Q

What are post infection syndromes?

A

diarrhoea changes gut flora, which may cause GI upset, diarrhoea and ongoing symptoms for a significant amount of time afterwards

29
Q

What is c. Diff infection?

A

Overgrowth or colonisation
Inflammatory gastroenteritis
Gr+ and forms spores – enable to survive well outside host
Mild diarrhoea to perforation and toxic megacolon (result of huge amounts of inflammation
produces as an immune response against the toxin), malnutrition
Diarrhoea, fever, not bloody, vomiting

30
Q

What are the main antibiotic causes of C.diff?

A

Clindamycin
Cephalosporins
Ciprofloxacin (and other fluoroquinolones)
Co-amoxiclav

31
Q

Who does C.diff usually affect?

A

Elderly/infirm paints (hospitals/nursing homes)

32
Q

What is the pathogenesis of C.diff?

A

Imbalance of regional flora caused by antibiotics
Acquisition of C. difficile
Increase in number of C. difficile in patients already colonised o Production of mucosa-damaging toxins (A and B)

33
Q

How is a diagnosis of C.diff made?

A

Toxin detection

Stool culture doesn’t establish the diagnosis as asymptomatic carriage in the elderly is common

34
Q

What is the management of C.diff?

A

Stop inciting antibiotics (if possible
Isolate patient - prevents environment becoming contaminated with C. difficile
spores and other patients becoming affected
Specific anti-C. difficile antimicrobials
• Oral metronidazole - 1st choice, anaerobic activity
• Oral vancomycin
• Oral fidaxomicin
• For 10-14days

35
Q

What are some other measures that can be taken to treat C.diff?

A

Probiotics (e.g. Saccharomyces cerevisiae) – used to try and repopulate healthy gut
flora
Faecal flora transplant – as a last resort to restore healthy gut flora, requires donor to
donate some faeces which is then tested to ensure correct microbiome is introduced

36
Q

What are prebiotics?
What is the prebiotic index and its purpose?
What do prebiotics promote?

A

chemicals that alter the structure of the microbiome by promoting growth of specific types of bacteria
Based on Mannan
PI (prebiotic index) = (Bif/Total) – (Bac/Total) + (Lac/Total) – (Clos/Total)
PI allows you to calculate the effectiveness of a specific chemical on the altering of
the gut flora
You want to promote bifidobacteria and lactobacilli, you want to supress
bacteroides and clostridium

37
Q

What are probiotics?

A

live cultures of organisms to repopulate gut flora after infection
Prevention of infections
• Direct effects on invading pathogens
• Indirect by stimulating immune function – e.g. sIgA production
Treatment of established infection
Use in conditions with a non-infective aetiology – e.g. chronic inflammatory bowel disease

Block 15 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions