Unit 3 Case 2

Question 1

What is Unit 3 Case 2 about?

Answer 1

There are 2 patients, both suffering from gastrointestinal infections. The first, Lena, who has returned from travelling. The timeline of symptoms indicates the patient has contracted gastroenteritis, due to enterotoxigenic Escherichia coli. She is treated successfully with oral rehydration therapy. The second patient suffers from Crohn’s disease. The patient develops Clostridium difficile enterocolitis due to the long term antibiotics they have taken.

Question 2

What is dehydration and what are some effects of dehydration?

Answer 2

Dehydration is when your body does not have as much water as it needs.

• effects can be feeling dizzy or lightheaded, feeling tired, increased urea concentration in urine
• With more serious longer-term effects being the formation of kidney stones, and heart problems

Question 3

What are the properties of Escherichia coli (E.coli)?

Answer 3

E.coli is a rod-shaped, gram-negative bacteria that infects the gastrointestinal tract

Question 4

What is the physiology behind vomiting (emesis)?

Answer 4

Located near the medulla oblongata are the chemoreceptor trigger zone (CTZ) and the vomiting centre. Activation if the CTZ via chemicals such as dopamine 2 and serotonin receptors activates the vomiting centre. The vomiting centre produces the vomiting reflex, causing the lower oesophagal sphincter to relax and epiglottis to close, diaphragm and abdominal muscles contract to increase intraabdominal pressure and cause the vomit to move up and out.

Question 5

What are some common types of pathogenic E.coli?

Answer 5

Shiga toxin-producing E.coli (STEC)
Enterotoxigenic E.coli (ETEC)
Enteropathogenic E.coli (EPEC)
Enteroaggregative E.coli (EAEC)
Enteroinvasive E.coli (EIEC)

Question 6

What are the symptoms of gastroenteritis?

Answer 6

Elevated white blood cell count, elevated C-reactive protein (CRP), elevated serum urea, lack of urine, high heart rate, dizziness, dehydration

Question 7

What is gastroenteritis?

Answer 7

Gastroenteritis is inflammation of the gastrointestinal tract- the stomach and small intestines.

Question 8

Where are nutrients absorbed into the blood?

Answer 8

Virtually all nutrients from the diet are absorbed into the blood across the mucosa of the small intestine, alongside water and electrolytes.

Question 9

Describe the absorption of nutrients in the small intestine

Answer 9

• Sodium and glucose are co transported via facilitated diffusion into the cell through apical SGLT1 glucose/sodium transporter.
• Glucose passively moves into the basolateral side. Sodium is transported out of the cell to the basolateral side of the cell while potassium is transported in- this requires ATP
• Potassium passively moves back out of the cell and chloride ions follow the gradient between cells-paracellular

Question 10

Describe the secretion of nutrients in the small intestine?

Answer 10

• Chloride passes through into the cell and is actively transported out to the lumen. This requires cAMP
• Potassium and sodium follow this movement into the cell and are recycled back to the basolateral side via active transport
• Sodium moves between cells following the electrochemical gradient set by the chloride ion movement
• A small amount of water can then enter the lumen via osmosis

Question 11

What is the mechanism of action of Picolax?

Answer 11

Contains 2 laxatives; sodium picosulfate which is a stimulant laxative and magnesium citrate which is an osmotic laxative.

• Sodium picosulfate has no effect on the GI tract until it is metabolised by gut bacteria into its active compound, which stimulates increased peristalsis
• Magnesium citrate causes water to be drawn into the lumen which stimulates defecation

Question 12

What is Picolax used for?

Answer 12

Picolax is used to treat constipation or as in this case to prepare the large bowel before colonoscopy or surgery

Question 13

What is the mechanism of action of prednisolone?

Answer 13

• It is a glucocorticoid which is used to reduce inflammation. It passes across the cell membrane to bind to glucocorticoid receptors in the cytoplasm
• This then dimerises and moves to the nucleus where it binds to glucocorticoid response elements in the DNA, altering gene expression
• Reducing the production of pro-inflammatory cytokines and IL-2 and increasing levels of anti-inflammatory cytokines e.g IL-10

Question 14

What is the mechanism of action of adalimumab?

Answer 14

It is a fully human monoclonal antibody that specifically binds to tumour necrosis factor-alpha (TNF-a). The monoclonal antibodies are highly specific to their target and will bind to the cytokine preventing it from binding to its receptor and reducing the downstream inflammatory effects of the cytokine
-disrupts TNF signalling attempting to encourage resolution of the inflammation

Question 15

What is the mechanism of action of amoxicillin?

Answer 15

It is a broad-spectrum beta-lactam antibiotic. It inhibits bacterial cell wall synthesis through competitive inhibition of penicillin-binding proteins that cross-link peptidoglycan strands. Bacteria are unable to build the cell wall and therefore undergo cell lysis

Question 16

What is dysentery?

Answer 16

Dysentery is an intestinal inflammation, primarily in the colon.

Question 17

What is the infection pathogenesis of common bacteria such as C.difficile and E.coli in food poisoning?

Answer 17

Food poisoning- the ingestion of preformed toxins in prepared food, from organisms that have colonised the substance and produced toxins in situ

Question 18

What is the infection pathogenesis of common bacteria such as C.difficile and E.coli in gastroenteritis?

Answer 18

The colonisation of the small bowel with organisms requires pathogenicity factors to evade the immune system. Once established, the replication of these organisms and subsequent toxin production or immune action will lead to dysregulated water absorption.
-leads to watery-diarrhoea, nausea and vomiting, and dehydration

Question 19

What is the infection pathogenesis of common bacteria such as C.difficile and E.coli in dysentery?

Answer 19

Invasion of the gastric mucosa following colonisation is more of a serious problem for the body. Destruction of the enterocytes can lead to the spread of the pathogen or toxin into the system circulation. Characterised by bloody diarrhoea and a greater rise in temperature than gastroenteritis

Question 20

What is rehydration therapy?

Answer 20

Is the process of replacing water and electrolytes into the body which has been lost
-In oral rehydration therapy a mixture of sodium, glucose, potassium and citrate are mixed with clean water and is drunk

Question 21

What is a gram stain used for?

Answer 21

A gram stain is used to tell whether a bacterium is gram-positive or gram-negative

Question 22

How is a gram stain carried out?

Answer 22

A sample is taken from a site of suspected infection or from certain body fluids e.g wound sample, blood test, urine test, sputum test
The sample is then placed on a slide and treated with the gram stain

Question 23

The gram stain stays purple, what does this indicate?

Answer 23

Gram-positive bacteria

Question 24

The gram stain turns pink or red, what does this indicate?

Answer 24

Gram-negative bacteria

Question 25

The gram stain turns pink or red, what does this indicate?

Answer 25

Gram-negative bacteria

Question 26

What is an ileocolic resection?

Answer 26

This is an operation to remove the terminal ileum, the last part of the small intestine and the first part of the colon.
-The surgeon then makes an anastomosis between the small intestine and remaining part of the colon using sutures or staples to make this join.

Question 27

What is Crohn’s disease?

Answer 27

A type of inflammatory bowel disease
-cause is unknown
-A long term condition
Symptoms include diarrhoea, stomach aches and cramps, and blood in poo

Question 28

What are some possible coping mechanisms for patients with long term illnesses?

Answer 28

Support groups, individual counselling sessions, or family counselling sessions as a family can help the mental recovery of patients suffering from long term illness

Question 29

What are the factors affecting adherence to medical regimes?

Answer 29

Social factors- low levels of education, social support or zero-hour contracts
Psychological factors-high anxiety/ depression, non-acceptance of illness, perceived stigma of the condition, distrust in treatment
Treatment factors- misunderstanding about treatment, the complexity of regime, poor communication between doctor and patient.