9.2 GI Infections

Question 1

4 benefits of the microbiome

Answer 1

1. Harmful bacteria cant colonise/compete for nutrients
2. Oroduces antimicrobials
3. Develops newborn immune system
4. Make vit K (byproduct kf bacteria metabolism)

Question 2

Which short chain fatty acids do bacteria in colon make, and whats their functions?

Answer 2

Butyrate- energy for colonocytes, regulates gut environment
Acetate- cholesterol metabolism
Propionate- regulates satiety

Question 3

Consequences of poor gut microbiota

Answer 3

Obesity
IBD
Poor chemotherapy response
Poor insulin response
(Less diversity)

Question 4

Which factors of lifestyle can negatively impact microbiota diversity?

Answer 4

-sweeteners
-gluten free diet if not coeliac
-ppi’s
-antibiotics in meat

Question 5

Faecal microbiota transplant
-what is it
-helps to treat?

Answer 5

Healthy faeces given to unwell person, replaces imbalanced bacteria

-c diff
-IBD
-crihns

Question 6

Where is the faeces from in Faecal microbiota transplant?

Answer 6

10-25 year old, no ABx or laxatives or diet pills, no GI disease, screened for HIV etc
1 hour

Question 7

Length of salmonella infection

Answer 7

2-3 days

Question 8

Describe the pathogenesis of salmonella

Answer 8

-enter enterocytes via endocytosis
-go to submucosa, taken up by macrophages
-carries to RES
-multiply intracellularly
-cause lymphoid hyperplasia
-reenter bowel via liver and gallbladder

Question 9

Is campylobacter microaerophilic?

Answer 9

Yes

Question 10

Incubation of campylobacter

Answer 10

1-7 days

Question 11

Type of diarrhoea in campylobacter

Answer 11

Profuse (due to cytotoxin), can be bloody

Question 12

Whos commonly affected by shigella?

Answer 12

Children under 5

Question 13

Why is shigella diarrhoea so bloody?

Answer 13

Kills colonocytes and forms abscesses in mucosa

Also mucus in diarrhoea

Question 14

Resolution of shigella

Answer 14

A week

Question 15

Pathogenesis of ET E coli

Answer 15

-adheres to enterocytes, makes enterotoxins
-hypersecretion of chloride ions from enterocytes
-water cleaves to lumen as Na+ also in lumen

Question 16

Commonest cause of travellers diarrhoea

Answer 16

ET E coli

Question 17

Which gram negative bacteria cause bloody diarrhoea?

Answer 17

Shigella
Campylobacter

Question 18

Which gram negative bacteria cause watery diarrhoea?

Answer 18

ET e coli
Slamonella

Question 19

Which gram negative bacteria can cause HUS?

Answer 19

Shigella
Campylobacter

Question 20

HUS

Answer 20

Anaemia
Thrombocytopenia
AKI

Question 21

What type of bacteria is c diff?

Answer 21

Gram positive, anaerobic, spore forming

Question 22

Main precipitating factor for c diff colonisation

Answer 22

Antibiotics

Question 23

C diff toxins and their actioms

Answer 23

A- enterotoxin that causes excess secretions and inflammation
B- cytotoxin kills meterocytes

Question 24

Symptoms of c diff infection

Answer 24

Asymptomatic
Varying diarrhoea severity
Abdo cramps

Question 25

Serious complications of c diff infection

Answer 25

Pseudomembranous colitis Toxic megacolon

Question 26

Whats Pseudomembranous colitis?

Answer 26

Complication of c diff, elecatedyellow plaques join to form a pseudomembrane

Question 27

C diff treatment

Answer 27

Remove offending antibiotic Fluid resus Metronidazole/vancomycin Probiotics (replace commensal bacteria)

Question 28

2 viral causes of gastroenteritis

Answer 28

Rotavirus Norovirus

Question 29

3 parasitic causes of gastroenteritis

Answer 29

Cryptosporidium Giardia Entamoeba

Question 30

Whos affected by rotavirus (also whos not?)

Answer 30

Under 5s Not adults as immunity lasts

Question 31

First symptom of rotavirus

Answer 31

Vomiting with fever

Question 32

Treatment of rotavirus

Answer 32

Manage dehydration

Question 33

Explain 3 mechanisms of rotavirsu causing diarrhoea

Answer 33

1. Increases chloride secretion -via cAMP so opens CFTR -Na+ follows and water by osmosis 2. SGLT1 disruption -redyced movementof Na+ and water, stay in lumen -hugher osmotic load exters osmotic presure -water moves by osmosis 3. Bursh border dysfunction -general malabsorption so increased osmotic pressure

Question 34

Where does norovirus infect?

Answer 34

Small intestibne, damages microvilli

Question 35

Why vomiting in norovirus?

Answer 35

Pressure of timach increases due to delayed gastric emptying, so vomiting releives the pressure

Question 36

Pathogenesis of cryptosporidium causing gastroenteritis

Answer 36

-ingestion of oocyst -resproduces inside epithelial cells of distal small intestine -excreted in faeces and cycle continues

Question 37

Type of diarrhoea in cryptosporidium

Answer 37

Watery, due to chlroide secretion and brush border affceted

Question 38

Incubation period for giardia

Answer 38

10 days

Question 39

Duration of abdo cramps in giardia

Answer 39

Up to 6 weeks

Question 40

Lifecycle of giardia

Answer 40

1 cyst ingested, stomach + oancreatic enxymes release parasite from cyst Damages proximal small intestine = diarrhoea 2. Parasite reformes cyst in colon Excreted and repeats cycle

Question 41

Treatment of giardia

Answer 41

ABx and fluid replacement

Question 42

Common deficiency after giardia

Answer 42

Lactase = kactose intolerance

Question 43

Symptoms of entamoeba

Answer 43

Asymptomatic 80% Diarrhoea, ,iver abscesses

Question 44

Highest prevalence of entamoeba

Answer 44

Developing countries

Question 45

Pathogenesis of entamoeba

Answer 45

-ingest cyst, excystaion in colon -trophozoites invade mucosa = bloody diarrhoea -can soread to lover and heart (abscesses) -pass out in faeces after cyst reforms

Question 46

Entamoeba treatment

Answer 46

Antiprotzoals/metronidazole Surgery if toxic megacolon

Question 47

Trophozoite

Answer 47

Activate dfeeding stage of entamoeba, not infective to others

Question 48

Whos given antibiotics cor travellers diarrhoea?

Answer 48

Immunocompromised

Question 49

Treatment of mild travellers diarrhoea

Answer 49

Hydration Antidarrhoeal agents

Question 50

Treatment of severe travellers diarrhoea (>6stools per day)

Answer 50

IV fluids ABx