Infectious Diarrhoea Flashcards
What is definition of gastro-enteritis?
3+ stools in 24 hrs PLUS one of fever, vomit, pain, blood/mucus stool
What is dysentery?
Large bowel inflammation + bloody stools
What are causative mechanisms of diarrhoea?
Toxins, invasion, others
What are defences against diarrhoea?
Age, hygiene, gastric acid, gut motility, gut immunity, normal flora
What are the 3 types of diarrhoea?
Non-inflammatory, Inflammatory, Mixed
What is non-inflammatory (secretory) diarrhoea? What is the treatment?
Toxin mediated
Watery stools, rapid dehydration
Tx = rehydration
What is inflammatory diarrhoea?
Treatment?
Bacterial infection
Inflammatory + toxin damage and mucosal destruction
Causes abdominal pain, fever, bloody stools, systemic upset
Tx = rehydration +/- antimicrobials
What is an example mixed diarrhoea?
C. difficile
What is the most common bacterial pathogen causing diarrhoea
Campylobacter
What pathogen causes the most hospital admissions due to diarrhoea?
Salmonella
Causes of infectious diarrhoea?
Contamination of foodstuffs e.g. chicken, poor food storage, travel related, person-to-person transmission
Patient assessment, what symptoms do you ask about?
Duration, frequency, consistency of diarrhoea
What risk factors are there for diarrhoea?
Food poisoning, occupation, travel, antimicrobials
What do you check on examination of a patient with diarrhoea?
Hydration status- BP, pulse, urine flow, skin turgor, muscle cramps
What are features of inflammation on a patient?
Fever, raised WCC
When is gastro-enteritis unlikely?
If diarrhoea present for over 2 weeks
What consequences are there due to fluid + electrolyte loss?
Severe dehydration (1-7 litres of fluid lost per day)
Hyponatraemia (sodium loss during fluid replacement with hypotonic solutions)
Hypokalaemia ( K+ loss in stool)
What investigations should be done?
Stool + blood culture, blood count (neutrophilia, haemolysis), renal function, sigmoidoscopy, abdo x-ray if distended, serology
Differential diagnosis?
Diarrhoea as a response to sepsis
IBD (duration > 2 weeks)
Spurious diarrhoea secondary to constipation
Carcinoma
Treatment for diarrhoea?
Oral rehydration - with salt / sugar IV saline Antimicrobials Fasting Treat complications
What are the features of campylobacter infection? (C. jejuni)
Incubation of up to 7 days, infection clears within 3 weeks (but can have positive stool test up to 6 weeks0
SEVERE abdo pain, +/- colitic picture
Rarely invasive
Post invective sequelae: Guillain barre syndorme, Reactive arthritis
What are the features of salmonella infection?
Symptom onset <48 h after exposure Diarrhoea lasts < 10 days <5% have positive blood culture 20% have positive stools at 20 weeks 27% experience IBS symptoms 6 months after
What are the features of E.Coli 0157?
Infection from e.g. contaminated meat/ Cattle reservoir
Frequent bloody stools
Produce a shiga-like toxin (SLT)
E. coli O157 stays in the gut but the toxin gets into the blood
Enterohaemorrhagic: haemorrhage within intestines
What toxin can cause HUS and what is HUS?
The shiga like toxin (SLT)
HUS = Haemolytic uremic syndrome
Causes haemolytic anaemia (caused by destruction of blood cells) + acute renal failure
What are the features of Shigella?
largely a childhood / travel disease
HUS and seizures can complicate it
Different serotypes set back development of a vaccine for Shigella
What other forms of E. Coli cause diarrhoea?
enteropathogenic
enterotoxic
enteroinvasive
What bacterial pathogens cause food poisoning?
Stap aureus
Bacillus cereus
Clostridium perfringens
What are the main pathogens of traveller’s diarrhoea?
Enterotoxigenic E. coli, campylobacter, shigella
How are parasites diagnosed?
By microscopy + PCO (parasites, cysts and ova tests)
Describe the features of rotavirus + its diagnosis?
Common in winter + children <5 years
Diagnosis by antigen detection
(note: Rotavirus vaccine used in developing world)
Describe the features of norovirus?
How is it diagnosed?
Faecal-oral transmission
winter vomiting disease
VERY infectious, common cause of outbreaks in hospitals + cruise ships
Diagnosis: PCR
Give two examples of intestinal parasites
Cryptosporidiosis
Giardia Lamblia
What are the features of cryptosporidiosis?
Caused by water-borne outbreaks (cattle = principal reservoir)
Cysts seems on microscopy
Self limiting, No Tx
What are the features of Giardia Lamblia?
present in contaminated water
causes diarrhoea, malabsorption, failure to thrive
Cysts seen on microscopy
Tx = metronidazole, tinidazole
Give an example of an imported parasite + describe its features
Entamoeba histolytica = Amoebic dysentery Cysts seen in asymptomatic patient Long term Cx= amoebic liver abscess Microscopy only 50% sensitive May mimic Ulcerative Colitis
What is the treatment for Amoebic dysentery?
10 days of metronidazole
What is an antibiotic associated diarrhoea?
Clostridium difficile infection
Describe the features of a Clostridium difficile infection (CDI)
Overgrowth of C. diff + production of toxins A (enterotoxin) and toxin B (cytotoxin)
What are the symptoms of a CDI?
Severity ranges from mild diarrhoea to severe colitis
What are the investigations for CDI?
Sigmoidoscopy, stool culture, toxin detection (33% false negative)
What is the treatment for CDI?
- Metronidazole
- Oral vancomycin (give if 2 or more severity markers)
- Fidaxomicin
How do you prevent CDI?
Reduction in broad spectrum antibiotics prescribing
Avoid the 4 C’s: Cephalosporins, co-amoxiclav, clindamycin, clarithromycin
Isolate symptomatic patients
Prevention with biotherapy
For what pathogens are routine bacterial cultures done?
Campylobacter + Salmonella
What indications are there for giving antibiotics?
Immunocompromised patients, severe sepsis, valvular heart disease, diabetes, chronic illness
