Infectious Diarrhoea Flashcards
Definitions of diarrhoea, gastroenteritis, dysentery.
Diarrhoea - fluidity, frequency
Gastroenteritis - three or more loose stools a day
Dysentery - large bowel inflammation, bloody stools
Non-inflammatory/secretory diarrhoea
- secretory toxin-mediated
- cholera - increases cAMP levels and Cl secretion
- enterotoxigenic E. coli (travellers’ diarrhoea)
Presentation of non-inflammatory diarrhoea
Frequent watery stools with little abdominal pain
Treatment of non-inflammatory/secretory diarrhoea
Rehydration mainstay of therapy
Inflammatory diarrhoea
- inflammatory toxin damage and mucosal destruction
- bacterial infection / amoebic dysentery
Inflammatory diarrhoea presentation
Pain and fever
Treatment of inflammatory diarrhoea
Antimicrobials may be appropriate but rehydration alone is often sufficient
Assessing patient with diarrhoea
-Symptoms and their duration
–>2/52 unlikely to be infective gastro-enteritis
-Risk of food poisoning
-Dietary, contact, travel history
-Assess hydration
–postural BP, skin turgor, pulse
-Features of inflammation (SIRS)
-fever, raised WCCFluid and electrolyte losses
Can be severe with secretory diarrhoea
- 1-7 l fluid per day containing 80-100 mmol Na - Hyponatraemia due to sodium loss - Hypokalaemia due to K loss in stool
Investigations for patients with diarrhoea
- stool culture +/- molecular or Ag testing
- blood culture
- Renal function
- blood count - neutrophilia, haemolysis (E. Coli O157)
- abdominal X-Ray/CT if abdomen distended, tender
Differential diagnosis of diarrhoea
- Inflammatory bowel disease
- Spurious diarrhoea -secondary to constipation
- Carcinoma
- Sepsis outside the gut
Sepsis outside the gut presentation
-Diarrhoea and fever
–Lack of abdo pain/tenderness goes against gastroenteritis
–No blood/mucus in stools
Gastroenteritis treatment
- rehydration
- oral rehydration with salt/sugar solution
- IV saline
Campylobacter gastroenteritis
-Campylobacter is the most common food born pathogen
-Up to 7 days incubation so dietary history may be unreliable
-Stools negative within 6 weeks
-abdominal pain can be severe
-<1% invasive
–Post-infection sequelae
-Guillain-Barre syndrome, Reactive arthritis
Salmonella gastroenteritis
- symptom onset usually <48 hrs after exposure
- diarrhoea usually lasts <10 days
- post-infectious irritable bowel is common
- prolonged carriage may be associated with gallstones
Salmonella gastroenteritis investigation results
- <5% positive blood cultures
- 20% patients still have positive stools at 20/52
Commonest salmonella isolates in the UK
- Salmonella enteritidis
- Salmonella typhimurium
E. coli O157
- produces Shiga toxin
- stays in the gut but the toxin gets into the blood
- toxin can cause hemolytic-uraemic (HUS) syndrome
E. coli O157 presentation
frequent bloody stools
Hemolytic-uraemic syndrome (HUS)
HUS characterised by renal failure, haemolytic anaemia and thrombocytopenia
Hemolytic-uraemic syndrome (HUS) treatment
Treatment supportive – antibiotics NOT indicated
Indication for antibiotics in gastroenteritis
- immunocompromised
- severe sepsis or invasive infection
- chronic illness e.g. malignancy
Clostridiodes difficile diarrhoea
- Patient usually gives history of previous antibiotic treatment – the “4 C antibiotics”
- Severity ranges from mild diarrhoea to severe colitis
- C. Diff produces enterotoxin (A) and cytotoxin (B) (inflammatory)
Clostridiodes difficile diarrhoea treatment
- metronidazole
- oral vancomycin
- Fidaxomicin (new and expensive)
- stool transplants
- surgery may be required
Clostridiodes difficile infection prevention
- Reduction in broad spectrum antibiotics
- Avoid 4 Cs
- Isolate symptomatic patients
- Wash hands between patients (spores resist alcohol rubs)
- Cleaning environment
4 C’s
- cephalosporins
- co-amoxiclav
- clindamycin
- ciprofloxacin
Clostridiodes difficile infection management
- Stop precipitating antibiotic (if possible)
- Oral metronidazole if no severity markers
- Oral vancomycin if 2 or more severity markers
Cholera
-a secretory diarrhoeal disease caused by the gram negative bacterium Vibrio cholera
Cholera presentation
-patients present passing large quantities of rice water stools
Cholera diagnosis
- basic laboratory tests non-specific
- culture of the organism is specific
- rapid dipstick tests are available
Cholera treatment
- most patients will recover if the effects of the ensuing profound volume depletion are combated by oral and/or intravenous rehydration
- antibiotics shorten duration and severity of disease, but rising rates of bacterial resistance are becoming problematic
Shigella infection
- easily spread by faecal-oral contact or by contaminated water or food
- usually presents as mild self limiting diarrhoeal illness
- HUS and seizures may complicate
- different serotypes hamper development of a universal vaccine
Rotavirus
- most common viral enteropath
- faecal-oral transmission
- infects mature enterocytes of villous body and tip (not crypts) with cell death and lactose intolerance
Rotavirus diagnosis
-antigen detection in stool
Norovirus
- very infectious -18 virus particles
- ward closures common – staff and patients affected
- strict infection control measures needed
Norovirus diagnosis
-PCR
Norovirus environmental association
-Institutional care, hospitals and care homes
Intestinal parasites - Cryptosporidium parvum - Cryptosporidosis
- outbreaks associated with contaminated drinking water supplies, fresh produce, swimming pools, children’s day care facilities and petting farms
- disease is self limiting in immunocompetent patients
- patients who are severely immunocompromised may suffer chronic, severe and intractable illness
Cryptosporidiosis presentation
- watery diarrhoea
- abdominal cramps
- loss of appetite
- low grade fever
- nausea and vomiting
- > 7 days
Cryptosporidiosis diagnosis
-detection of oocytes, antigens, or DNA in stool samples
Giardia duodenalis transmission
- direct contact with cattle/cats/dogs/other people
- food/water contaminated with faeces
Giardiasis presentation
- diarrhoea
- abdominal bloating and discomfort
- malabsorption
- failure to thrive
Giardiasis diagnosis
-detection of cysts or trophozoites in stool sample
Giardia lambda is associated with:
-contaminated water supplies
Entamoeba histolytica (causes amoebiasis) presentation
- may mimic ulcerative colitis
- diarrhoea
- abdominal pain
- fever
Giardiasis treatment
- metronidazole
- tinidazole
Entamoeba histolytica (causes amoebiasis) diagnosis
- detection of a Entamoeba histolytica antigen or
- DNA in stool or antibodies against the parasite in serum (invasive disease)
Entamoeba histolytica (causes amoebiasis) complications
- spread from the intestine can cause liver abscess
- extension from liver abscess can lead to pleural and pericardial effusion
- rarely, brain abscesses may occur
Entamoeba histolytica (causes amoebiasis) treatment
- metronidazole (or tinidazole)
- luminal agent to clear colonisation (paromomycin)
Entamoeba histolytica is associated with:
-foreign travel and poor hygiene
Use of blood cultures in infectious diarrhoea
Rarely helpful, but should be done in all patients to exclude invasive Campylobacter / Salmonella spp.
Use of toxin testing in infectious diarrhoea
To confirm C. difficile infection
Use of stool cultures in infectious diarrhoea
-to isolate bacterial pathogens e.g. Campylobacter sp., Salmonella sp., Shigella, E.coli
Use of stool microscopy for infectious diarrhoea
- best for parasitic causes
- on stool culture requests, specify that you’re looking for ova, cysts and parasites, along with any relevant travel history
Use of viral PCR/antigen testing for infectious diarrhoea
- to confirm norovirus / rotavirus infection
