Infectious diarrhoea

Question 1

How is diarrhoea defined?

Answer 1

Increased frequency and fluidity as defined by the patient - subjective

Question 2

How is gastro-enteritis defonined?

Answer 2

Objectively defined as 3 or more loose stools per day with accompanying features

Question 3

What accompanying features come with gastro-enteritis?

Answer 3

Abdominal pain

Blood in stool

Question 4

What is dysentry?

Answer 4

Large bowel inflammation with blood stools

Question 5

What are the 7 stages on the bristol stool chart?

Answer 5

1. Seperate hard lumps
2. Sausage shaped but lumpy
3. Sausage shaped with cracks on the surface
4. Like a sausage, smooth and soft
5. Soft blobs with clear cut edges
6. Fluffy pieces with ragged edges - mushy
7. Entirely liquid

Question 6

What is the epidemiology of gastro-enteritis?

Answer 6

Contamination of food stuffs
Poor storage of produce
Travel related infections
Person to person spread

Question 7

What is the most common bacterial organism to cause gastroenteritis?

Answer 7

Campylobacter

Question 8

What food is the most common cause of food poisoning?

Answer 8

Undercooked chicken

Question 9

What is the most common cause of GI infection?

Answer 9

Viruses

Question 10

What pathogen causes the most food poisoning hospital admissions each year?

Answer 10

Salmonella

Question 11

What defences do we have against enteric infections?

Answer 11

Hygiene
Stomach acidity
Normal gut flora
Immunity

Question 12

What can have adverse effects on stomach acidity’s effect on defence against enteric infections?

Answer 12

Antacids and infections - raise pH

Question 13

What are the 2 main types of diarrhoeal illness?

Answer 13

Secretory/non inflammatory - cholera

Inflammatory - Shigella dysentry

Question 14

What is the difference between secretory and inflammatory diarrhoea at presentation?

Answer 14

Secretory is enormous volumes of watery stool with generally no other systemic upset, inflammatory may have other symptoms such as blood in the stool

Question 15

What is the mechanism for secretory diarrhoea?

Answer 15

Secretory toxin-mediated - Increased cAMP levels and chloride secretion

Question 16

How is non inflammatory diarrhoeal illness treated?

Answer 16

Rehydration - little role for antimicrobials

Question 17

How does inflammatory diarrhoea typically present?

Answer 17

Diarrhoea with abdominal pain and fever

Question 18

How is inflammatory diarrhoea treated?

Answer 18

Rehydration alone is often sufficient but antimicrobials may also be appropriate

Question 19

How long does a gastroenteric infection typically last?

Answer 19

Less than 2 weeks

Question 20

What drop in postural blood pressure would you indicate dehydration?

Answer 20

20mmHg from lying to standing

Question 21

What should you assess patients for when they present?

Answer 21

Symptoms and their duration
Risk of food poisoning
Hydration
Features of inflammation

Question 22

What factors could put a patient at risk of food poisoning?

Answer 22

Diet
Contact
Travel history

Question 23

How is hydration of patients assessed?

Answer 23

Check postural change in BP
Skin turgor
Pulse - check for tachycardia

Question 24

What features of inflammation would you look for in a patient?

Answer 24

Fever

Raised WCC

Question 25

What features would a dehydrated infant show?

Answer 25

``` Sunken eyes and cheeks Sunken fontanelle Few/no tears Decreased skin turgor Dry mouth or tongue ```

Question 26

Why is it important to make sure fluid given to patients with secretory diarrhoea has plenty of electrolytes?

Answer 26

They lose a lot of electrolytes as a result of cAMP activating so these must be replaced to avoid hyponatraemia

Question 27

What assessments can be done on the patient?

Answer 27

``` Stool culture Blood culture Renal function Blood count Abdominal X-Ray/CT if distended or tender abdomen ```

Question 28

What blood counts should be done?

Answer 28

Neutrophilia Haemolysis Electrolytes

Question 29

How many stool samples is typically recommended for culture?

Answer 29

3

Question 30

Why should imaging be done on a patient with distension/tenderness?

Answer 30

They may be at risk of perforation

Question 31

What are differential diagnoses for infectious diarrhoea?

Answer 31

IBD Spurious diarrhoea - secondary to constipation Carcinoma Diarrhoea can occur with sepsis outside the gut

Question 32

What would differentiate diarrhoea caused by sepsis?

Answer 32

Lack of abdominal pain/tenderness | No blood/mucous in stool

Question 33

What is oral rehydration therapy?

Answer 33

Drinking water with salts to restore both fluid and electrolyte balance

Question 34

Why does oral rehydration have glucose in it?

Answer 34

Not all salt would be absorbed, but the gut has a sodium glucose cotransporter, which allows more sodium to be absorbed with glucose

Question 35

What are characteristics of campylobacter gastroenteritis?

Answer 35

7 days incubation, dietary history may be unreliable Stools negative within 6 weeks Can have severe abdominal pain Almost never invasive into blood

Question 36

What condition can happen post infection of campylobacter?

Answer 36

Guillan Barre syndrome

Question 37

How is culture done to determine if an infectious organism is present?

Answer 37

Growing culture in a variety of media and incubation conditions and takes 3 days to complete all tests

Question 38

What are characteristics of salmonella gastroenteritis?

Answer 38

Symptom onset within 48 hours of exposure Diarrhoea lasts less than 10 days Around 5% of cases have positive blood cultures Many patients still have positive stools at 20 weeks

Question 39

What is associated with prolonged carriage of salmonella?

Answer 39

Gallstones

Question 40

What are the 2 main species in the salmonella genus?

Answer 40

S.enterica | S.bongori

Question 41

How is salmonella screened in the lab?

Answer 41

It is a lactose non-fermenter

Question 42

How is E.coli O157 spread?

Answer 42

Contaminated meat or person to person spread

Question 43

Why do blood cultures come up negative with E.coli O157 even with symptoms of sepsis?

Answer 43

The organism stays in the gut - its toxin gets into the blood

Question 44

What is a major complication of E.coli O157 toxin being in the blood?

Answer 44

It can lead to Haemolytic uraemic syndrome

Question 45

What is Haemolytic Uraemic Syndrome (HUS)?

Answer 45

Haemolytic anaemia and renal failure

Question 46

Why are antibiotics contraindicated with E.coli O157?

Answer 46

Because they cause the organism to lysis and release greatly higher quantities of toxin

Question 47

What are common bacteria that cause infectious diarrhoea?

Answer 47

Campylobacter Salmonella E.coli O157 Shigella

Question 48

What patients with infectious diarrhoea should receive antibiotics?

Answer 48

Immunocompromised Severe sepsis Patients with chronic illness

Question 49

How do C.difficile diarrhoea cases typically present?

Answer 49

History of previous antibiotic treatment | Severity ranges from mild to severe

Question 50

How is C.difficile treated?

Answer 50

Metronidazole Oral vancomycin Fidaxomicin Stool transplant

Question 51

Why is vancomycin taken orally for C.difficile but IV for almost everything else?

Answer 51

It is very poorly absorbed, meaning it stays in the gut and has little systemic effect but a great effect on the C.difficle

Question 52

How can C.difficile infection be prevented?

Answer 52

Reduce broad spectrum antibiotic prescribing Isolate symptomatic patients Wash hands with soap between patients Cleaning environment

Question 53

What are the 4Cs of antibiotics that increase C.difficile risk?

Answer 53

Cephalosporins Co-amoxiclav Clindamycin Ciprofloxacin

Question 54

How are protozoa infections diagnosed?

Answer 54

Microscopy - Parasites, cysts, and ova

Question 55

What are symptoms of giardia duodenalis infection?

Answer 55

Diarrhoea Gas Malabsorption Failure to thrive

Question 56

How is Giardia duodenalis infection treated?

Answer 56

Metronidazole

Question 57

What are symptoms of cryptosporidium parvum?

Answer 57

Diarrhoea Nausea and vomiting Abdo pain

Question 58

How is viral diarrhoea diagnosed?

Answer 58

Antigen detection in stool

Question 59

Where is norovirus commonly picked up?

Answer 59

Hospitals Schools Care homes Cruise ships

Question 60

How is norovirus diagnosed?

Answer 60

PCR