Infectious Diarrhoea Flashcards
What is dysentery?
Large bowel inflammation, bloody stools
Causes of gastro-enteritis
Contamination of foodstuffs (intensively farmed chicken and campylobacter)
Poor storage of produce (Bacterial proliferation at room temperature)
Travel-related infections (salmonella)
Person-to-person spread (norovirus)
What is the most common bacterial pathogen in GI infection?
Campylobacter
Which pathogen causes most hospital admissions?
Salmonella
Defences against enteric infections
Hygiene
Stomach acidity (antacids and infection)
Normal gut flora (C. difficile diarrhoea)
Immunity (HIV + salmonella)
What are the types of clinical features of diarrhoeal illness?
Non-inflammatory/secretory (cholera)
Inflammatory (shigella dysentery)
Mixed picture (C. diff)
Non-inflammatory diarrhoeal illness
Secretory toxin-mediated
Frequent watery stools with little abdo pain
Rehydration mainstay of therapy
Mechanism of diarrhoea in cholera
Increased cAMP results in loss of Cl from cells along with Na and K
Osmotic effect leads to massive loss of water from the gut
Inflammatory diarrhoeal illness
PAIN AND FEVER
Inflammatory toxin damage and mucosal destruction
Bacterial infection/amoebic dysentery
Antimicrobials may be appropriate but rehydration alone is often sufficient
Fluid and electrolyte losses in secretory diarrhoea
Hyponatraemia due to Sodium loss with fluid replacement by hypotonic solutions
Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)
Infectious diarrhoea differential diagnosis
IBD
Spurious diarrhoea (secondary to constipation)
Carcinoma
Treatment of infectious diarrhoea
Oral rehydration with salt/sugar solution
IV saline
Campylobacter gastroenteritis post-infective sequelae
Guillain-Barre syndrome
Reactive arthritis
Routine bacterial culture
Difficult to find pathogen in the midst of complex normal flora
Selective and enrichment methods of culture necessary - variety of media and incubation conditions
Takes 3 days to complete all tests
Which two species of campylobacter are responsible for most infections?
C. jejuni
C. coli
What is prolonged carriage of salmonella associated with?
Gallstones
How long after exposure to salmonella is symptom onset?
Usually <48hrs
How long does diarrhoea last with salmonella gastroenteritis?
Usually <10 days
What are the two species in the salmonella genus?
S. enterica
S. bongori
How is E. coli illness typically characterised?
Frequent bloody stools
What toxin is produced by E. coli?
Shiga toxin (also produced by shigella spp)
Pathophysiology of E. coli infection
E. coli stays in the gut but the toxin travels to the blood which can cause haemolytic-uraemic syndrome (HUS)
How is HUS characterised
Haemolytic anaemia
Renal failure
Thrombocytopenia
Treatment of HUS
Supportive
Antibiotics NOT indicated
When are antibiotics appropriate in gastroenteritis?
Immunocompromised
Severe sepsis or invasive infection
Chronic illness e.g. malignancy
(Not indicated for healthy patient with non-invasive infection)
Treatment of C. diff
Metronidazole
Oral vancomycin
Fidaxomicin (new and expensive)
Stool transplants
Surgery may be required
Presentation of C. diff infection
From mild diarrhoea to severe colitis
What are the 4 C antibiotics that result in CDI?
Cephalosporins
Co-amoxiclav
Clindamycin
Ciprofloxacin
UK protozoa
Giardia duodenalis
Cryptosporidium parvum
Entamoeba histolytica
Long term complication of amoeba
Amoebic liver abscess
WHat are the signs that diarrhoea is caused by sepsis outside of the gut?
Lack of abdo pain/tenderness goes against gastroenteritis
No blood/mucus in stools
Which bacterial gastroenteritis presents most quickly?
Salmonella - <48 hrs after exposure
Campylobacter - up to 7 days
