Gastroenteritis

• Most common cause of significant adult gastroenteritis world-wide is bacterial infection.

Organisms to be discussed:• Salmonella• Campylobacter jejuni• Shigella• EHEC• Vibrio• Yersinia• Staph aureus• Bacillus cereus• Clostridium.

Mechanisms

Salmonella

• S. enteritidis and S. typhimurium.

• Commensals in poultry and chicken.

• Transmitted via contaminated foodstuffs and water.

• Affects large and small bowel.

• Typical symptoms starts between 12–48 hours after infection.

• Spontaneous resolution usually occurs in 3–6 days.

• Young children and elderly at risk of significant dehydration.

• Treat with ciprofloxacin 500mg po bd reduced duration and severity of symptoms.

Enteric Fever

• Occur world-wide mainly in India and Africa.

• Typhoid by Salmonella typhi.

• Parathyphoid by S. paratyphi A, B or C.

• Incubation period is 10–14 days.

Clinical features

• Invades small bowel (peyer’s patches) to regional LN to blood.

• In early stages include:

1. Abdominal tenderness

2. Hepatosplenomegaly

3. Lymphadenopathy

4. Scanty maculopapular rash (‘rose spots’).

Complications

• (Usually in 3rd week of illness)• meningitis• lobar pneumonia• osteomyelitis• intestinal perforation• intestinal haemorrhage

• After clinical recovery they become convalescent carriers.

• Usual site of carriage is the gall bladder

Diagnosis

• Culture of S. typhi or S. paratyphi from the patient.

• Blood culture is positive in most cases in the first 2 weeks.

• Bone marrow culture is more sensitive than blood culture, but is rarely required.

Management

• Ciprofloxacin 500 mg twice daily) are now the treatment of choice.

• Azithromycin if resistant.

Campylobacter jejuni

• A common cause of childhood gastroenteritis in developing countries.

• Affects small and large bowel.

• Incubation period 2-4 days.

• Self limiting in 3-5 days.

• If severe treat with azithromycin 500mg po od.

Shigella

• Causes classical bacillary dysentery.• S. dysenteriae, S. flexneri and S. sonnei.• Only small numbers needed to be ingested to

cause illness (<200).• Symptoms start 24–48 hours after ingestion • Frequent small-volume stools containing blood

and mucus.• Self-limiting in 7–10 days.• Resistance to antibiotics is widespread.

Enterohaemorrhagic Escherichiacoli (EHEC)

• Also known as VTEC.• Secretes a toxin (Shiga-like toxin 1)

which affects vascular endothelial cells in the gut and in the kidney.

• Incubation period of 12–48 hours.• Patient may develop TTP or HUS.• Treatment Is supportive.• Avoid antibiotics as may precipitate

HUS.

Vibrio

• Vibrio cholera-next slide.

• Vibrio parahaemolyticus causes acute watery diarrhoea after eating raw fish or shellfish that has been kept for several hours without refrigeration.

• Self limiting up to 10 days.

Cholera• Pure enterotoxigenic diarrhoea.

• Gram-negative bacillus, Vibrio cholerae.

• Common in Bangladesh, India and South East Asia.

• Transmission is by the faeco-oral route

• Proliferates in the small intestine.

• Releases exotoxin which produces massive secretion of isotonic fluid into the intestinal lumen.

• Releases serotonin (5-HT) from enterochromaffin cells in the gut, which activates a neural secretory reflex in the enteric nervous system.

• Incubation period few hours to 6 days.• Majority have mild illness.

• In severe cases: 1. profuse painless diarrhoea 2. ‘rice water’ stool.3. vomiting4. hypovolemic shock.

• Children may present with convulsions owing to hypoglycaemia.

• Diagnosis is largely clinical.

• Demonstration of organism in stool not diagnostic.

• Stool and rectal swabs should be taken for culture to confirm the diagnosis.

Treatment

• Mainstay of treatment is rehydration.

• Tetracycline or erythromycin x 3/7.

• Help to eradicate infection, decrease stool output, and shorten the duration of the illness.

• However, a single dose of ciprofloxacin or azithromycin (each 1 g) is a better choice.

• Prevention by good hygiene and improved sanitation.

Yersinia

• Yersinia enterocolitica.

• Human disease arise either via contaminated food products,ie: pork, or direct animal contact.

• Watery diarrhoea, dysentery and mesenteric adenitis.

• Self-limiting but ciprofloxacin may shorten the duration.

• Y. pseudotuberculosis causes mesenteric adenitis and terminal ileitis.

Staphylococcus aureus

• Produce a heat-stable toxin (enterotoxin B) which causes massive secretion of fluid into the intestinal lumen.

• Onset of symptoms is rapid, often within 2–4 hours of consumption.

• Causes violent vomiting, followed within hours by profuse watery diarrhoea.

• Symptoms have usually subsided within 24 hours.

Bacillus cereus

• Produces two toxins.

• One causes diarrhea the other causes severe vomiting.

• ‘fried rice poisoning’

Clostridial infections

• Clostridium difficile causes antibiotic-associated diarrhoea, colitis and pseudomembranous colitis.

• Gram-positive,anaerobic, spore-forming bacillus.• Normal flora in 3-5% general population.• Up to 20% in hospitalized patients.

• Produces 2 toxins:Toxin A (enterotoxin)Toxin B (cytotoxic)

• Almost all antibiotics have been implicated but the present increase has been attributed to the overuse of quinolones (e.g. ciprofloxacin).

Clinical features

• Diarrhoea can begin anything from 2 days to a month after taking antibiotics.

• The colonic mucosa is inflamed and ulcerated and can be covered by an adherent membrane-like material (pseudomembranous colitis).

Diagnosis

• Detecting A or B toxins in the stools by ELISA techniques.

Treatment

• Discontinue causative antibiotic.

• Treat with metronidazole 400 mg po tds or

• Oral vancomycin 125 mg po QID.

• Isolation of patients with C. difficile.

• Clostridium perfringens infection is due to inadequately cooked food.

• Releases enterotoxin causing watery diarrhoea with severe abdominal pain, usually without vomiting.

Travellers Diarrhea

Possible questions

• By which mechanism does vibrio cholera cause gastroenteritis?

• Name 3 organisms causing watery diarrhea and profuse vomiting.

• Clinical features of thyphoid fever.

• In thyphoid, when does complications develop?

• Common site for carriage of s.thyphi?

• What is the most common cause of childhood gastroenteritis in developing countries.

• A person had only eaten very small amount of food at a stall, becomes unwell with diarrhea. Passing frequent small-volume stools containing blood and mucus. Most likely organism?

• Consequence of infection from EHEC?

• Which toxin does EHEC secrete?

• A person becomes very unwell with profuse painless diarrhoea, ‘rice water’ stool, vomiting and ended up in ICU with hypovolemic shock. Most likely organism?

• Which organism has the potential to cause mesenteric adenitis?

• A person becomes unwell with vomiting and diarrhea only after several hours of eating dinner. Most likely organism?

• A person eats fried rice takeaway and becomes sick afterwards. Most likely organism?

• A person took ciprofloxacin a month ago and now develops diarrhea. Most likely organism? Treatment choice?

• What is the most common organism in Traveller’s diarrhea?