Infectious diarrhoea Flashcards
What is the objective definition of gastro-enteritis?
Three or more loose stools/day
Accompanying features
What are the obvious features of dysentery?
Large bowl inflammation
Bloody stools
What are examples of the epidemiology of gastro-enteritis?
Contamination of foodstuffs - chicken and campylobacter
Poor storage of produce - bacterial proliferation at room temperature
Travel-related infections
Person-to-person spread - norovirus
What is the commonest cause of gastro-enteritis?
Viruses
What is the commonest bacterial pathogen causing gastro-enteritis?
Campylobacter
What is the pathogen which causes the most hospital admissions per year?
Salmonella
Which type of food is linked to the most cases of food poisoning per year?
Poultry meat
In order, what are the most common pathogen isolates in Scotland?
Campylobacter
Salmonella
E.coli O157
What are the best defences against enteric infections?
Hygiene
Stomach acidity
Normal gut flora
Immunity
Why are you at more risk of gastro-enteritis if on antacids?
Lose protection of the acidity of the stomach
Why might you get diarrhoea if you are on antibiotics for C.diff?
Taking antibiotics can kill “good” bacteria, allowing C. difficile to multiply and release toxins that damage the cells lining the intestinal wall, causing diarrhoea, abdominal pain, and fever as well as other symptoms
Which group of patients are particularly susceptible to salmonella infections?
Immunosuppressed e.g. HIV
What are the different categories of clinical features of diarrhoeal illness?
Non-inflammatory
Inflammatory
Mixed picture
What is an example of a non-inflammatory/secretory diarrhoeal illness?
Cholera
What is the character of a non-inflammatory/secretory diarrhoeal illness?
Lots of watery diarrhoea
Little abdo pain
What is an example of an inflammatory diarrhoeal illness?
Shigella dysentery
What is the character of an inflammatory diarrhoeal illness?
Inflammatory toxin damage and mucosal destruction
Pain and fever
More systemic upset
Tender abdomen
What is the mechanism of diarrhoea in cholera (non-inflammatory)?
Bacterial toxins activate adenyl cyclase and cAMP is made
Increased cAMP levels result in loss of Cl from cells along with Na and K
Osmotic effects leads to massive loss of water from the gut
What is the treatment for non-inflammatory and inflammatory diarrhoeal illness?
Oral rehydration therapy
What factors should be considered when assessing a patient with diarrhoeal illness?
Symptoms and duration - >2wks unlikely infective gastro-enteritis
Risk of food poisoning
Assess hydration - postural BP, skin turgor, pulse
Features of inflammation - fever, raised WCC
Postural drop is defined as a reduction in systolic BP by how much?
20mmHg
What are the clinical signs in a paediatric patient with diarrhoeal illness?
Sunken eyes and cheeks Decreased skin turgor Sunken fontanelles Few or no tears Dry tongue or month Sunken abdomen
In which subtype of diarrhoea can fluid and electrolyte losses be particularly severe?
Secretory/non-inflammatory diarrhoea
How much fluid can be lost /day in a patient with secretory diarrhoea?
1-7L
How can a patient with diarrhoeal illness have hypokalaemia?
Due to K loss in stool
What investigations can you do for a patient with diarrhoeal illness?
Stool culture +/- molecular of Ag testing
Blood culture
Renal function
Blood count: neutrophilia, haemolysis (E.coli O157)
Abdominal XR/CT if abdomen distended/tender
What might a stool antigen test look for?
H.pylori infection
What are some differential diagnoses for diarrhoeal illness?
IBD (blood in stool)
Spurious diarrhoea
Carcinoma
Sepsis outside the gut
What is spurious diarrhoea?
Chronic constipation causes the bowel to be blocked by hard-packed faeces, some liquid manages to pass = spurious diarrhoea
Common in elderly
What are the signs that diarrhoea and fever are being caused by sepsis outside the gut?
Lack of abdomen pain/tenderness (goes against gastroenteritis)
No blood/mucus in stools (goes against IBD)
What is the common treatment of gastro-enteritis?
Oral rehydration with salt/sugar solution
IV saline
How long can campylobacter gastroenteritis be incubated?
Up to 7 days
After how many weeks would the stools be negative for campylobacter infection?
Within 6 weeks
What is the commonest bacterial cause of gastroenteritis?
Campylobacter infection
What are differential diagnoses for abdominal pain caused by gastroenteritis?
Appendicitis
Perforation
What post-infectious complications can occur as a result of campylobacter gastroenteritis?
Guillain-Barre syndrome
Reactive arthritis
How long does it take to complete all tests for bacterial cultures to find pathogens responsible for diarrhoeal illnesses?
3 days
What types of detection are used to find bacterial pathogens?
Molecular detection
Antigen detection
What are the two species of campylobacter which cause the most infections?
C.jejuni
C.coli
What is the commonest cause of bacterial food poisoning in the UK?
Campylobacter
What may contain campylobacter which may cause infection?
Chicken, contaminated milk, puppies
What pathogen type of gastroenteritis is more likely to hospitalise a patient?
Salmonella gastroenteritis
When is the symptom onset usually for salmonella gastroenteritis?
<48 hrs after exposure
How long do diarrhoeal symptoms usually last for salmonella gastroenteritis?
<10 days
What percentage of salmonella gastroenteritis have positive blood cultures?
<5%
What may prolonged carriage of positive blood cultures in stools be associated with?
Gallstones
What is a common complication of salmonella gastroenteritis?
Post-infectious irritable bowel
How is the character of IBD differentiated from the character of salmonella gastroenteritis?
IBD: few loose sttols in morning, better rest of day
SGE: up during night and all day
What are the two species of salmonella in the genus?
S.enterica
S.bongori
What are the commonest salmonella isolates in the UK?
S.enteritidis
S.typhimurium
How does E.coli infection spread?
Contaminated meat
Person-to-person
How is E.coli O157 typically characterised?
Frequent bloody stools
What toxin does E.coli O157 produce?
Shiga toxin
How does the toxin spread?
E.coli O157 stays in gut, toxin gets into the blood
What syndrome can the shiga toxin cause?
Hemolytic-uraemic (HUS) syndrome
What does hemolytic-uraemic (HUS) syndrome cause?
Haemolytic anaemia
Renal failure
Thrombocytopenia
What is the treatment for hemolytic-uraemic (HUS) syndrome?
Mainly supportive
Dialysis
No antibiotics
Plasmapharesis/IVIG
What are the symptoms of hemolytic-uraemic (HUS) syndrome?
Abdominal pain Bloody diarrhoea Fever Seizures Lethargy
How does Shiga toxin cause HUS?
Shiga toxin can enter your bloodstream and cause damage to your blood vessels
What are other bacteria which can cause diarrhoeal illness?
Shigella
E.coli - other forms
What are the 4 species of Shigella?
S.sonnei
S.flexneri
S.boydii
S.dysenteriae
What are other bacterias that cause food poisoning outbreaks?
Staph aureus Bacillus cereus (re-fried rice) Clostridium perfringens (undercooked meat left out)
When are antibiotics indicated for patients with gastroenteritis?
Immunocompromised
Severe sepsis or invasive infection
Chronic illness (malignancy)
With what history should you suspect a patient has C.diff diarrhoea?
History of previous antibiotic treatment
What are the treatments for C.diff diarrhoea?
Metronidazole Oral vancomycin Fidaxomicin Stool transplants Surgery
Why is oral vancomycin usually ineffective and why is it effective in C.diff diarrhoea?
Oral vancomycin usually ineffective as doesn’t pass through semi-permeable membranes
In C.diff diarrhoeal illness oral vancomycin is good as it stays in the gut
What 4 C’s (anitbiotics) should be avoided to avoid C.diff infection?
Cephalosporins
Co-amoxiclav
Clindamycin
Ciprofloxacin
How can C.diff infections be prevented?
Avoid 4C’s
Reduction in broad spectrum antibiotic prescribing
Antimicrobial management team (AMT) and local antibiotic policy
Isolate symptomatic patients
Hand hygiene
Cleaning environment
How are C.diff infections managed?
Stop precipitating antibiotic
Treatment algorithm - oral metronidazole
Oral vancomycin if 2+ severity markers
How are parasitic infections usually diagnosed?
Microscopy
How should a stool request be sent for a suspected parasitic infection?
Parasites, cysts and ova
P,C&O
What parasite causes giariasis?
Giardia duodenalis
What are the symptoms of a giardia duodenalis infection/giardiasis?
Diarrhoea
Gas
Malabsorption
Failure to thrive
How is giardia duodenalis transmitted?
Direct contact with cattle/dogs/cats/other people
Food/water contaminated with faeces
How is giardia duodenalis detected?
Cysts seen on stool microscopy
String test
Trophozoites seen on duodenal biopsy
How is giardiasis treated?
Metronidazole
What are the symptoms of a Cryptosporidium parvum infection?
Diarrhoea
Nausea and vomiting
Abdominal pain
How is Cryptosporidium parvum carried?
> 150 species of animals
How is Cryptosporidium parvum infection spread?
Infected animals/faeces
Contaminated water/food
How is Cryptosporidium parvum diagnosed?
Oocysts seen on microscopy
What does Entamoeba histolytica cause?
Amoebic dysentery
Invasive extraintestinal amoebiasis
Usually no bowel symptoms
How is an Entamoaeba histolytica infection diagnosed?
Microscopy: trophozoites or cysts
Antibody detection in serum
How is an Entamoaeba histolytica infection treated?
Metronidazole
Luminal agent to clear colonisation
What is a long term complication of Entamoaeba histolytica infection?
Amoebic liver abscesses
What are viral diarrhoea causes?
Rotavirus
Norovirus
Adenovirus
What is the diagnostic test for rotavirus?
Antigen detection in stool
What age are patients who usually get rotavirus?
<5yrs
When do babies get the rotavirus vaccine?
2 doses:
8 weeks
12 weeks
What virus is a common cause outbreaks?
Norovirus
Where are norovirus outbreaks most likely to occur?
Hospitals
Community: schools, care homes
Cruise ships
How is norovirus diagnosed?
PCR
