Infectious Diarrhoea Flashcards
How is Gastro-enteritis defined?
3+ loose stools/day
Accompanying features
How is Dysentery defined?
Large bowel inflammation
Bloody stools
How is gastro-enteritis spread?
Contaminated foodstuffs
Poor food storage
Travel-related infections
Person-person spread
What gastro-enteritis bacteria is associated with contaminated foodstuffs?
Campylobacter
Which foodstuff is most commonly associated with food poisoning?
Poultry
What are the defences against enteric infections?
Hygiene
Stomach acidity
Normal gut flora
Immunity
What are the clinical features of diarrhoeal illness?
Inflammatory/non-inflammatory
Mixed
What are the clinical features of non-inflammatory diarrhoeal illness?
- Secretory Toxin-mediated
- Frequent watery stooles with little abdo pain
- Rehydration mainstay of therapy
What toxins are involved in non-inflammatory diarrhoeal illness?
Cholera - ↑cAMP and C1 secretion
Enterotoxigenic E. coli
What is the mechanism of diarrhoea in cholera?
↑cAMP = loss of Cl, Na and K
Osmotic effect leads to massive water loss
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
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)
How is hydration assessed?
Postural BP Skin turgor Pulse Dry mouth Sunken eyes/cheeks/fontanelle Few/no tears
How severe can fluid loss be in gastroenteritis?
1-7L/day
80-100mmol Na+
Hyponatremia
Hypokalemia
How should a gastroenteritis patient be investigated?
Stool culture Blood culture Renal function Blood count - neutrophilia, haemolysis Abdominal X-ray/CT
Haemolysis and gastroenteritis is associated with what?
E. coli O157
What is the DDx of gastroenteritis?
Inflammatory Bowel disease
Spurious/Overflow diarrhoea
Carcinoma
Sepsis
Diarrhoea and fever due to sepsis would likely present how?
Lack of abdominal pain/tenderness
No blood/mucus in stool
How is gastroenteritis diagnosed?
Rehydration therapy - salt/sugar
What post-infection sequelae are associated with Campylobacter gastroenteritis?
Guillain-Barre
Reactive arthritis
Why is dietery history unreliable in Campylobacter gastroenteritis?
Up to 7 days incubation
What tests can be used in stool testing?
Molecular detection
Antigen detection
What species are most common in Campylobacter gastroenteritis?
C. jejuni (90%)
C. coli (9%(
What is the most common source of Campylobacter gastroenteritis?
Chicken
Contaminated milk
Puppies
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