Gastroenterology

Bowel Infections

Antibiotic associated diarrhoea

Introduction

  • Clostridium difficile is an anaerobic spore forming bacterium

Characteristics

  • Large gram positive anaerobic terminal spore forming rods
  • Irregular shaped colonies on blood agar
  • Found in the soil or in the bowel or in the environment as spores

Aetiology

  • Toxin A - an enterotoxin and cytotoxic acts on gut mucosa
  • Toxin B - a cytotoxin which cause the death of colonic luminal cells
  • Third substance that inhibits bowel motility
  • Together these cause ulceration and diarrhoea
  • The use of broad spectrum antibiotics is associated with PMC especially cephalosporin, clindamycin and ampicillin
  • Ribotype 027 is associated with a very virulent form of infection with higher toxin production and quinolone resistance

Clinical

  • Diarrhoea may begin within 4-10 days of antibiotic treatment but may be delayed up to 6 weeks
  • Asymptomatic to mild diarrhoea to pseudomembranous colitis
  • Copious liquid stool with Fever, malaise
  • Abdominal pain and distension and toxic megacolon, perforation and death

Investigations

  • FBC and WCC elevated CRP elevated
  • U&E may suggest dehydration
  • Sigmoidoscopy may show yellow adherent plaques
  • Anaerobic culture on cycloserine, cefoxitin and fructose (CCFA) media
  • Stools - presence of toxins A and B
  • Sensitivity - Metronidazole /Vancomycin

Management

  • Prevention : Transmission can be reduced by good hand washing using alcohol hand gels in most infections but not with Clostridium difficile spores. Soap and water is advised.
  • Treatment : Patients should be isolated at first suspicion and receive either oral metronidazole 400 mg tds or oral Vancomycin 125 mg qds until assays have proven or disproved diagnosis for up to 10 days
  • Loperamide and any drug which slows GI transit should be avoided.
  • The main worry is diarrhoea and exacerbation of co-existing diseases
  • Involve gastroenterologists and surgeons in management. May require acute surgical management especially with toxic megacolon or perforation.

Acute infectious diarrhoea

Introduction

  • Very common - the key is to maintain hydration
  • Admit and isolate the elderly and frail and those unable to manage oral intake

Bacterial organisms cause D&V

  • Bacillus cereus - fried rice and meats - onset less than 6 hours
  • Campylobacter jejuni - chicken, daily, contaminated water
  • Clostridium botulinum - home canned food
  • Clostridium perfringens
  • E Coli 0157:H7 : Beef, water, unpasteurised food, farm animals : Bloody diarrhoea. Develop haemolytic uraemic syndrome
  • Staphylococcus aureus - cream pastry, salds, chicken - onset less than 6 hours
  • Salmonella - chicken/eggs, milk, juice : Sickle cell anaemia can be severe
  • Shigella - any water/food
  • Vibrio cholera- seafood, water borne
  • Vibrio parahaemolyticus - raw shellfish
  • Yersinia - pork, milk

Viral organisms cause D&V

  • Rotavirus - kills 1,000,000 per year mostly children with severe diarrhoea. Seen in Hospitals and other institutions. Damages small intestine enterocytes.
  • Norovirus - (Norwalk like virus ssingle stranded RNA) collection of people together e.g. holiday group or hospital ward. Single stranded RNA. Nausea, vomiting, watery diarrhoea. Evidence of small intestinal mural inflammation.
  • Adenovirus - paediatric disease.
  • Hepatitis A

Other organisms cause D&V

  • Giardiasis
  • Entaemoeba histolytica
  • Cryptosporidiosis - AIDS

Clinical

  • Acute diarrhoea, vomiting, malaise
  • Usually more than one person
  • Abdominal tenderness

Differential

  • Appendicitis - atypical presentation with retrocaecal appendicitis can cause abdominal pain and some diarrhoea
  • Acute colitis - Ulcerative, Crohn's disease, Clostridium difficile
  • Systemic infection
  • Toxins often from fish e.g. Ciguatera and scombroid
    • Histamine release with rash, flushing, diarrhoea
    • Onset usually less than 1 hour

Management

  • Oral or IV Rehydration
  • Loperamide is used
  • Metronidazole for Giardia, trichenlla, amoebiasis
  • Avoid antibiotics for E Coli 0157:H7 as may increase HUS

Complications

  • Disseminated infection with Salmonella esp Sickle cell anaemia
  • Haemolytic uraemic syndrome with E coli 0157:H7
  • Guillain Barre syndrome with campylobacter

Giardiasis

Introduction

  • Infection with Giardia lamblia (intestinalis or duodenalis)
  • A flagellated protozoan in either cysts or trophozoite forms
  • Commoner but not isolated to only the tropics
  • Areas of poor sanitation and water control
  • Those with immunodeficiencies are more susceptible (IgA)

Aetiology

  • Trophozoites attach to small intestinal epithelium
  • Do not penetrate intestinal wall or cause necrosis
  • Cause subtotal villous atrophy of small intestine

Clinical

  • May be an acute to chronic diarrhoeal illness
  • Nausea, diarrhoea
  • Bloating, malabsorption
  • Weight loss, steatorrhoea

Investigations

  • Malabsorption - low folate, low albumin
  • Hypochromic microcytic anemia is seen with chronic infection
  • OGD and duodenal aspirates show trophozoites
  • Subtotal villous atrophy on biopsy
  • Stool microscopy shows cysts

Management

  • Metronidazole 2 g daily for 3 days

Vibrio cholera

Introduction

  • Notifiable Infection with gram negative bacillus Vibrio cholera
  • Epidemics once seen throughout Western world but now isolated to areas of overcrowding and poor sanitation
  • Pathogenicity due to release of cholera toxin

Characteristics

  • Comma shaped bacillus with a single polar flagellum
  • Found in saltwater. Facultative anaerobes
  • Oxidase positive (unlike enterobacteriaceae) and grows in alkaline conditions
  • Divided by their "O" types : O1 is the main cause of cholera
  • O139 strains of El Tor biotype cause cholera non 01 strains may occasionally cause a less severe diarrhoea
  • Over 150 serotypes based on O antigen

Source

  • Affects man only with no animal hosts
  • Spread by infected faeces entering the water source or direct Faeco oral spread

Virulence

  • Cholera toxin is composed of one A subunit and five B subunits
  • Toxin subunit B adheres to intestinal surface receptor GM1 ganglioside receptors
  • Toxin subunit A stimulates adenylate cyclase and increases cAMP causing increased chloride loss and reduced sodium uptake
  • There is torrential loss of isotonic fluid 'rice water' leads to profound dehydration

Pathogenicity

  • Sudden onset rice water stools with dehydration, hypovolaemia and shock
  • Vomiting and abdominal pain is mild
  • Death in up to 50% of untreated patients
  • non 01 strains may occasionally cause a less severe diarrhoea

Investigations

  • Gram stain of stools may show curved gram-negative rods
  • Alkaline broth used to grow organisms selectively from faeces
  • Stool cultures with pH > 8 with a elective media

Management

  • Support with oral rehydration therapy or Intravenous fluids
  • ORT - Mixture of water + salt + glucose
  • This exploits a separate Na/Glucose uptake mechanism
  • Tetracycline for 3 days
  • Ciprofloxacin may shorted illness
  • Identification of source and prevention

Amoebiasis

Introduction

  • Is due to the protozoan Entamoeba histolytica
  • Cyst stage - infective, a trophozoite stage which is causes invasive disease
  • Cysts are acquired from faecally contaminated water or uncooked food
  • Cysts release trophozoites in the small intestine
  • These pass to the colon to produce flask like Colonic ulcers
  • Trophozoites can pass via the portal vein ot the liver to form a liver abscess

Clinical

  • Lower GI bleeding can occur but perforation is rare
  • May cause constipation or mild intermittent diarrhoea
  • Toxic megacolon
  • Chronic infection with stricture
  • Inflammatory mass an Amoeboma around sigmoid or caecum can be mistaken for tumour
  • Amoebic liver abscess as organisms pass via portal vein to liver.
  • Patient is pyrexial , malaise, RUQ pain
  • Rare cause of brain abscess

Investigations

  • Diagnosis confirmed with amoebic fluorescent antibody test (FAT)
  • Microscopy of stool shows motile trophozoites containing red blood cells.
  • Liver abscess - raised ALP
  • USS or Abdominal CT to lok for abscess

Management

  • Metronidazole 800 mg po tds for 5 days for amoebic colitis
  • Metronidazole 400 mg tds for 10-14 days for liver abscess.
  • This is followed by Diloxanide for 10 days to clear the bowel of parasites.
  • Occasionally liver aspiration required produces anchovy paste, chocolate coloured fluid Prevention
  • Drink bottled water + good personal hygiene
  • There is no effective vaccine

Cryptosporidum

Introduction

  • Chronic diarrhoea in AIDS patients
  • Travellers diarrhoea

Aetiology

  • Water spread,resistant to chlorination
  • Ingested oocyte activated by gastric enzymes
  • Sodium loss, chloride release and increased leakiness of gap junctions cause diarrhoea

Clinical

  • Chronic Diarrhoea in AIDS
  • Acute diarrhoea in travellers or where there is contaminated water
  • Loss of appetite, nausea and abdominal pain and then foul watery diarrhoea

Investigations

  • Oocysts in stool
  • HIV test and CD4 count with chronic diarrhoea

Management

  • Prevent spread by good hand hygiene and boiling water
  • Supportive
  • Treat AIDS where relevant