Infectious Diarrhoea Flashcards
Define Diarrhoea
SUBJECTIVE
A condition in which faeces are discharged from the bowels frequently and in a liquid form.
Define Dysentry
OBVIOUS
Infection of the intestines resulting in severe diarrhoea (sometimes with the presence of blood and mucus in the faeces.)
Define Gastroenteritis
OBJECTIVE
3+ stools in 24 hours plus at least one of the following:
- Fever
- Vomiting
- Pain
- Blood / Mucus in Stools
What defense mechanisms do we have against dysentery and gastroenteritis?
- Age
- Hygiene
- Gastric Acid
- Gut Motility
- Normal Flora
- Gut Immunity
What are the two main mechanism of diarrhoea?
- Toxin
- Invasion
What are the types of diarrhoea?
Non-Inflammatory (cholera)
Inflammatory (shigella)
Mixed picture (C. difficile)
What is non-inflammatory diarrhoea?
- Toxin-Mediated
- Watery stools, rapid dehydration, relatively little abdominal pain.
- Rehydration therapy is main treatment
What is inflammatory diarrhoea?
- Bacterial Infection
- Bloody stools, systematic upset, abdominal pain.
- Rehydration is main treatment. Antimicrobials may be required.
What two organism contamination are often associated with intensely farmed livestock?
- Campylobacter
- Salmonella
What are the main factors which increase the prevalence of GI infections?
- Farming
- Storage
- Transport
- Poor Sterilisation
- Manual cross-infection
- Raw egg consumption
What is the incidence of Salmonella and Campylobacter in the UK?
100 / 100,000
What is a “novel” organism?
“Any living organism that possesses a novel combination of genetic material obtained through the use of modern biotechnology” - Basically GMO shit.
List two epidemics centred around novel organisms.
- Listeria Monocytogenes
- E. Coli O157
What would you look for in patient assessment?
Symptoms: Duration of diarrhoea. Frequency and “quality” of stool.
Risk Factors: food, occupation, travel, antimicrobials, contacts, institution.
Examination of hydration and SIRS: Pulse. Fever. Skin turgor. Urine flow. Patient appearance. Muscle cramps.
What’s SIRS?
Systemic inflammatory response syndrome (SIRS) is an inflammatory state affecting the whole body.
What investigations do you do for diarrhoea?
- Stool and Blood Culture
- Renal function
- Blood count (haemolysis)
- Sigmoidoscopy
- X Ray
- Serology
What are some differentials with a patient presenting with Diarrhoea?
- Diarrhoea as part of response to sepsis.
- Inflammatory bowel disease (If Duration > 2 Weeks)
What are treatment options for diarrhoea?
- Rehydration
- Fasting
- Antimicrobials
- Treatment of complications
What are the characteristics of Salmonella?
- Symptom onset usually less than 48h after exposure and diarrhoea.
- <5% of cases have positive blood cultures.
- Extraintestinal manifestations uncommon, but potentially fatal consensus view on antibiotic treatment.
- 20% have persistently positive stools at 20 / 52
- 27% have IBS symptoms at 6 months.
What are the characteristics of Campylobacter?
- Most common foodborne pathogen.
- Incubation up to 7 days.
- Infection clears within 3 weeks.
- Severe abdominal pain +/- colitic picture.
- Rarely invasive (immunocompromised) <1%.
- Post Infective sequelae
What are the characteristics of E.Coli O157:H7?
- Enterohaemmorhagic E.coli
- Excretion over three weeks after symptoms.
- Produces SLT (shiga-like toxins)
- HUS largely a complication in children and elderly.
- 5 to 9 days between onset of diarrhoea and HUS
What pathogen is a model for toxin-mediated diarrhoea?
Cholera
- Antimicrobial Resistance
- Vaccine
What are the characteristics of Shigella?
- Largely a disease of childhood / travel.
- HUS and seizures may complicate.
- Widespread quinolone use against shigellosis in developing world leading to resistance.
- Different serotypes hamper the development of a universal vaccine.
What is traveller’s diarrhoea?
- About 1/3 travellers develop a bout of diarrhoea.
- Usually lasts less than 1 week, but persistent diarrhoea in 1-3%
- Significant shortening by antibiotics.
- 80% of tourist infections are caused by E.Coli, Campylobacter and Shigella.
What is viral gastro-enteritis?
- Rotavirus is the most common viral enteropath
- More than 800,000 deaths in children under 5 years of age.
- Faecal Oral transmission
- Infects mature enterocytes of villous body and tip, with cell deaths and lactose intolerance.
What are the 3 main intestinal parasites do they want you to know?
- Cryptosporidiosis
- Giardia
- Entamoeba histolytica
Characteristics of cryptosporidiosis?
- Water-borne outbreaks.
- Cattle is the principal reservoir.
- Self-limiting (but often protracted illness in non-compromised patients).
Characteristics of Giardia?
- Present in surface water.
- Asymptomatic cyst carriers.
- Treatment: Metronidazole & Tinidazole.
Characteristics of Entamoeba histolytica?
- May mimic ulcerative collitis.
- Treat symptomatic disease with 10/7 metronidazole and furamide for cyst carriage.
Characteristics of antibiotic associated diarrhoea?
- Can range from mild diarrhoea to severe colitis.
- 5% to 10% of patients given antimicrobials develop diarrhoea.
- Usually the overgrowth of C.diff and production of toxins A and B (enterotoxin and cytotoxin)
What % of antibiotic associated diarrhoea is caused by Clostridium difficile?
10-15%
- 7% of patients carry c.diff on admittance, and 28% leave with it.
How do you test for c.diff infection?
- Sigmoidoscopy (underrated)
- Stool culture and toxin detection (33% false negative though).
- PMC can occur with negative toxin tests.
How do you treat c.diff?
- Metronidazole
- Vancomycin
- Teicoplanin
- Prevention with biotherapy.
What are the steps to haemolytic-uraemic syndrome?
Toxin binds to globotriaosylceramide
Platelet activation stimulated
Micro-angiopathy results
attachment to endothelial, glomerular tubule and mesangial cells.
What is Norovirus?
Commonest cause for viral diarrhoea.
How do you diagnose and deal with Norovirus?
Diagnosis via PCR
Very infectious
Ward closures common - Staff and other patients are affected/
Strict infection control measures are needed.
