Infectious Diarrhoea Flashcards by Peter Savage

How is Gastro-enteritis defined?

3+ loose stools/day

Accompanying features

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How is Dysentery defined?

Large bowel inflammation

Bloody stools

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How is gastro-enteritis spread?

Contaminated foodstuffs
Poor food storage
Travel-related infections
Person-person spread

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What gastro-enteritis bacteria is associated with contaminated foodstuffs?

Campylobacter

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Which foodstuff is most commonly associated with food poisoning?

Poultry

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What are the defences against enteric infections?

Hygiene
Stomach acidity
Normal gut flora
Immunity

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What are the clinical features of diarrhoeal illness?

Inflammatory/non-inflammatory

Mixed

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What are the clinical features of non-inflammatory diarrhoeal illness?

Secretory Toxin-mediated
Frequent watery stooles with little abdo pain
Rehydration mainstay of therapy

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What toxins are involved in non-inflammatory diarrhoeal illness?

Cholera - ↑cAMP and C1 secretion

Enterotoxigenic E. coli

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What is the mechanism of diarrhoea in cholera?

↑cAMP = loss of Cl, Na and K

Osmotic effect leads to massive water loss

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What are the clinical features of inflammatory diarrhoeal illness?

Pain and fever - inflammatroy toxin damage and mucosal destruction
Bacterial infection/amoebic dysentery
Antimicrobials may be appropriate
Rehydration often sufficient

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What must be assessed in a patient with gastroenteritis?

Symptoms and duration
Risk of food poisoning (Diet, contact, travel)
Assess hydration
Assess for inflammation (SIRS)

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How is hydration assessed?

Postural BP
Skin turgor
Pulse
Dry mouth
Sunken eyes/cheeks/fontanelle
Few/no tears

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How severe can fluid loss be in gastroenteritis?

1-7L/day
80-100mmol Na+
Hyponatremia
Hypokalemia

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How should a gastroenteritis patient be investigated?

Stool culture
Blood culture
Renal function
Blood count - neutrophilia, haemolysis
Abdominal X-ray/CT

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Haemolysis and gastroenteritis is associated with what?

E. coli O157

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What is the DDx of gastroenteritis?

Inflammatory Bowel disease
Spurious/Overflow diarrhoea
Carcinoma
Sepsis

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Diarrhoea and fever due to sepsis would likely present how?

Lack of abdominal pain/tenderness

No blood/mucus in stool

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How is gastroenteritis diagnosed?

Rehydration therapy - salt/sugar

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What post-infection sequelae are associated with Campylobacter gastroenteritis?

Guillain-Barre

Reactive arthritis

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Why is dietery history unreliable in Campylobacter gastroenteritis?

Up to 7 days incubation

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What tests can be used in stool testing?

Molecular detection

Antigen detection

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What species are most common in Campylobacter gastroenteritis?

C. jejuni (90%)

C. coli (9%(

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What is the most common source of Campylobacter gastroenteritis?

Chicken
Contaminated milk
Puppies

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How does Salmonella gastroenteritis present?

Symptoms <48hrs Diarrhoea <10 days <5% +ve blood cultures Positive stools up to 20 weeks

Prolonged Salmonella carriage is associated with what?

Gallstones

What post-infection sequelae is associated with Salmonella gastroenteritis?

Post-infectious irritable bowel

What species are most commonly responsible for Salmonella gastroenteritis?

S. enterica | S. bongori

What tests are used for culturing salmonella?

Lactose non-fermenters Antigen tests Biochemical tests

What are the most common salmonella isolates in the UK?

Salmonella enteritidis | Salmonella typhimurium

Salmonella typhi and paratyphi are responsible for what?

``` Enteric fever (not gastro-enteritis) (Typhoid, Paratyphoid) ```

What is E. coli O157 associated with?

Infection from contaminated meat or other people

How does E. coli O157 present?

Illness with frequent bloody stools | Haemolytic-uraemic syndrome (HUS)

What is the mechanism for E. coli O157 gastroenteritis?

Shiga toxin enters the blood, bacteria stays in gut

Shiga toxin is produced by what pathogens?

E. coli O157 | Shigella

How does Haemolytic-uraemic syndrome (HUS) present?

``` Renal failure Haemolytic anaemia Thrombocytopenia Bloody diarrhoea Seizures Abdominal pain ```

How is Haemolytic-uraemic syndrome (HUS) treated?

Supportive - antibiotics not indicated Dialysis IVIG/Plasmapharesis

Haemolytic-uraemic syndrome (HUS) is caused by what?

E. coli Shiga toxin

What is the mechanism of Haemolytic-uraemic syndrome (HUS)?

Shiga toxin stimulates platelet activation, leading to microangiopathy

Shigella is associated with what?

Gastroenteritis

Which Shigella species are associated with Gastroenteritis?

S. sonnei - nursery outbreaks S. flexneri S. boydii S. dysenteriae

What are the less common cause of food poisoning outbreaks? What are their sources?

``` Staph aureus (toxin) Bacillus cereus (refried rice) Clostridium perfringens (undercooked meat) ```

When are antibiotics indicated in gastroenteritis?

Immunocompromised Severe sepsis/invasion Chronic illness

How does C. diff diarrhoea present?

Previous history of antibiotics | Mild diarrhoea to severe colitis

What antibiotics are associated with C. diff?

``` "4 C's" Clindamycin Cephalosporins Co-amoxiclav Ciprofloxacin ```

What is the mechanism for C. diff diarrhoea?

Enterotoxin (A) | Cytotoxin (B)

How is C. diff infection treated?

``` Stop precipitating antibitics Metronidazole oral vancomycin (if >2 severity markers) Fidaxomicin Stool transplants Surgery ```

How is C. diff infection prevented?

``` Avoid prescribing broad-spec antibiotics Avoid 4Cs Antimicrobial management team policy Hygiene Patient isolation ```

How are parasites diagnosed?

Microscopy: | Stool sample with "parasites, cysts and ova"

What parasites are associated with gastroenteritis?

Protozoa | Helminths

What protozoans are associated with gastroenteritis in the UK?

Giardia duodenalis (/lamblia)

Giardia duodenalis gastroenteritis presents how?

Diarrhoea Gas Malabsorption Failure to thrive

How is Giardia duodenalis gastroenteritis diagnosed?

Cysts on stool microscopy Duodenal biopsy String test

How is Giardia duodenalis gastroenteritis treated?

Metronidazole

How is Giardia duodenalis gastroenteritis transmitted?

Direct contact with animals/people | Contaminated food/water

How is cryptosporidium parvum gastroenteritis diagnosed?

Oocysts on microscopy

Which UK protozoans are associated with gastroenteritis?

Cryptosporidium parvum Giardia duodenalis Entamoeba histolytica - imported

How does cryptosporidium parvum gastroenteritis present?

Diarrhoea N+V Abdo pain

How is cryptosporidium parvum gastroenteritis transmitted?

Animals | Contaminated water/food (9 cysts needed for infection)

How is cryptosporidium parvum gastroenteritis treated?

None usually required

How does Entamoeba histolytica infection present?

Amoebic dysentery Invasive extraintestinal amoebiasis much later Liver abscess No bowel symptoms

How is Entamoeba histolytica infection diagnosed?

Antibody detection | Stool microscopy "hot stool"

How is Entamoeba histolytica infection treated?

Metronidazole | Luminal agent

Which viruses are commonly associated with diarrhoea?

Rotavirus Norovirus Adenovirus

How does Rotavirus present?

Children <5 Winter Antigen in stool

How does Norovirus present?

Vomiting and diarrhoea Winter Hospitals Community centres

How is Norovirus diagnosed?

PCR

How is Norovirus managed?

Ward closure | Strict infection controls