Infectious diarrhoea part 1 (plus a bit of part 2 by accident)

Question 1

What symptoms are hallmark of diarrhoea?

Answer 1

Increased fluidity and frequency of stools

Question 2

Describe the bowel habit seen with gastroenteritis?

Answer 2

3 or more loose stools/day

Will have accompanying features/symptoms

Question 3

Describe the bowel habit seen with dysentery?

Answer 3

Quite obvious

Large bowel inflammation with bloody stools

Question 4

What causes infectious diarrhoea?

Answer 4

1) Contamination of foodstuffs
* Intensively farmed chicken and campylobacter
2) Poor storage of produce
* Ie storing food at room temperature causing bacterial proliferation
3) Travel-related infections e.g. Salmonella
4) Person-to-person spread e.g Norovirus

Question 5

Give an example of a cause of infectious diarrhoea that is spread through person to person contact

Answer 5

Norovirus

Question 6

What causes infectious diarrhoea, viruses or bacteria?

Answer 6

Viruses are commonest cause with campylobacter being the commonest bacterial pathogen

Question 7

What are the most common food-borne pathogens?

(ie the ones that cause food poisoning)

Answer 7

Campylobacter is the most common foodborne pathogen

Salmonella is the pathogen that causes the most hospital admissions

Question 8

What type of meat is most linked to food poisoning?

Answer 8

Poultry

(Chiquen and turkey)

Question 9

What age group is most at risk of getting/dying of infectious diarrhoea?

Where in the world is the mortality rate highest?

Answer 9

Children

death rate highest in certain parts of Africa

Question 10

What strain of E.coli is famously pathogenic?

Answer 10

E.coli O157

Question 11

What are the defences against enteric infections?

Answer 11

Hygiene

Stomach acidity

Normal gut flora

Immunity

Question 12

What are the types and features of non-inflammatory infectious diarrhoea?

Answer 12

Examples of non-inflammatory ID causing organisms:

1. Cholera - (Vibrio cholerae)
2. E.coli - (travellers diarrhoea)

Frequent, watery stools with little abdominal pain

Question 13

What is the general approach to treating non-inflammatory infectious diarrhoea?

Answer 13

Rehydration therapy

Question 14

Describe the mechanism of diarrhoea in cholera?

Answer 14

Cholera increases cAMP levels inside of epithelial cells

Increased cAMP results in loss of Cl^- from cells along with Na⁺ and K⁺

Osmotic effect leads to massive water loss into the lumen (ie diarrhoea)

Question 15

Describe the clinical features of diarrhoeal illness and what causes these features

Answer 15

Watery, frequent stools - for aforementioned reason

Inflammatory toxin damage and mucosal destruction causes PAIN and FEVER

Question 16

How do assess patients with infectious diarrhoea?

Answer 16

Symptoms and duration

Risk of food poisoning - travel, diet, contact

Assess hydration - postural BP, skin turgor, pulse

Features of inflammation (SIRS) - fever, raised WCC

Question 17

What features on examination of a neonate may indicate infectious diarrhoea?

Answer 17

Fever etc

Decreased skin turgor

Sunken eyes and cheeks

Sunken fontanelle

Dry mouth or tongue

Sunken abdomen

Question 18

What is the effect of diarrhoea on fluid and electrolyte balance?

Answer 18

Can cause severe loss of fluid and electrolytes

Which causes Hyponatraemia and Hypokalaemia

Question 19

How much fluid can patients lose with severe diarrhoea?

How much Sodium?

How much Potassium?

Answer 19

1 - 7 Litres of fluid containing 80 - 100 mmol Na+

Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)

Question 20

What investigations are done to assess patients with infectious diarrhoea?

Answer 20

• Stool culture +/- molecular or Ag testing
• Blood culture
• Renal function
• Blood count - neutrophilia, haemolysis (E. Coli O157)
• Abdominal X-Ray/CT if abdomen distended, tender

Question 21

What are the differential diagnoses for infectious diarrhoea and why?

Answer 21

Inflammatory bowel disease

Spurious (overflow) diarrhoea

Carcinoma

Diarrhoea and fever occurring secondary to sepsis outside of the gut

Question 22

What is spurious diarrhoea?

Answer 22

Diarrhoea secondary to constipation

Hx of alternating constipation & diarrhoea

Usually in elderly people

Question 23

If a patient presents with severe diarrhoea and fever - how would you differentiate between infectious diarrhoea or sepsis outside of the gut?

Answer 23

Lack of abdominal pain/tenderness

• this goes against Gastroenteritis

No blood/mucus in stool

• would show lack of inflammation etc of intestinal mucosa

Question 24

How is Gastroenteritis (infectious diarrhoea) treated?

Answer 24

Rehydration therapy:

• Oral rehydration solution - NaCl & glucose solution
• or IV Saline

Antibiotics sometimes needed for infectious gastroenteritis depending on the organism

Question 25

What features are indicative of campylobacter gastroenteritis?

Answer 25

All the normal symptoms + severe abdominal pain Incubation period of up to 7 days - so dietary history may be unreliable

Question 26

What other conditions can arise after campylobacter gastroenteritis?

Answer 26

Guillain-Barre syndrome Reactive arthritis

Question 27

What two species of Campylobacter cause the most cases of C. gastroenteritis in the UK?

Answer 27

C. jejuni (90%) C. coli (9%)

Question 28

How are campylobacteria transmitted/caught?

Answer 28

Chiquens Milk Puppies Commonest cause of bacterial food poisoning in the UK

Question 29

What characterises infection with E.coli O157?

Answer 29

Typical illness characterised by **frequent bloody stools**

Question 30

What is Shiga toxin?

Answer 30

It is the toxin produced by E.coli O157 and Shigella spp. E. coli O157 stays in the gut but Shiga toxin is what gets into the blood Shiga toxin can cause Haemolytic-uraemic syndrome (HUS)

Question 31

What is haemolytic-uraemic syndrome?

Answer 31

Syndrome caused by Shiga toxin - usually following E.coli diarrhoea Characterised by: - Renal failure - Haemolytic anaemia - Thrombocytopenia Most common cause of acute renal failure in children

Question 32

What other symptoms would be seen in Haemolytic uraemic syndrome?

Answer 32

The symptoms caused by the infection/Shiga toxin in the first place: * Bloody diarrhoea * Abdo pain * Fever * Seizures * Lethargy

Question 33

What is the treatment route for HUS?

Answer 33

_Mainly supportive:_ IV fluids blood transfusion dialysis if required Antibiotics not indicated

Question 34

What are the less common causes of food poisoning (and all this infectious diarrhoea stuff)

Answer 34

Staph aureus - (toxin) Bacillus cereus - (re-fried rice) Clostridium perfringens - (undercooked meat/cooked food left out - toxin accumulates in spore formation)

Question 35

When should antibiotics be prescribed for infective gastroenteritis?

Answer 35

Indicated in gastroenteritis if: * Immunocompromised * Severe sepsis or invasive infection * Chronic illness - ie malignancy *Not indicated for healthy person with non-invasive infection*

Question 36

Clostridium difficile infection is a rarer infection which is potentially serious What causes it? How severe can it be?

Answer 36

_C.diff diarrhoea_ Happens following broad spectrum antibiotic treatment (4 C's - incl clindamycin, cephalosporins) Ranges from mild diarrhoea to severe colitis - sometimes requiring surgery

Question 37

What toxins do C.diff produce?

Answer 37

enterotoxin (A) and cytotoxin (B) (inflammatory)

Question 38

How can Clostridium difficile infection treated?

Answer 38

Oral **Metronidazole** - first line Oral **Vancomycin** - if severe/not responding to Metronidazole Bezlotoxumab - alternative