Gastroenteritis Flashcards
What pathogens can cause gastroenteritis that I should know about?
Campylobacter Salmonella E coli 0157 C diff Listeria Shingella Norovirus Rotavirus
What are the general risk factors for GI infection?
Malnutrition (micro nutrient) deficiency Closed/semi closed communities (preschools, cruise ships) Exposure to contaminated food, water Winter congregating (more time spent indoors) Age <5 Not breastfed Older age Travel
If a patient is on acid supression, which organisms are more likely?
Yersinia H pylori (tolerant of acid) C diff Cholera Salmonella Campylobacter Listeria
What are the most common organisms in immunosuppressed patients?
Salmonella, campylobacter
Shingella
(all shed in faeces for longer)
Other uncommon organisms, MAK (micobacterium avian complex), CMV (cytomegalovirus))
Gut microbiome and genetics play a role in predisposing to infection. WHat are 2 genetic associations with GI infection?
IL8 promoter variants and severe C diff
O blood group and cholera
What does the pathogenic bacteria do to cause an infection?
Adherence/attachment to the mucosa
Cellular invasion
Production of exotoxins
Changes epithilial cell physiology
Loss of brush boarder, digestive enzymes and cell death
Increased intestinal motility, net fluid secretion, influx of inflammatory cells +/- intestinal haemorrhage
What is the inoculum size?
Median infecting dose required to cause disease in 50% of individuals
What does a low inoculum dose imply?
More infectious spread
What can affect the inoculum dose?
pH and gastric motility
What is diarrhoea?
> 3 unformed stools per day with no other cause (laxatives, excess stimulants (coffee))
Stool holds the shape of container
Departure from normal bowel habit
Which ‘types’ on the bristol stool chart are classified as diarrhoea?
types 5, 6, 7
What is dysentery?
Type of gastroenteritis.
Inflammation of the intestine, esp colon, causing diarrhoea associated with blood and mucus. Associated with fever, abdo pain, recal tenesmus
What is recal tenesmus?
Feeling of incomplete defication
Which type of gastroenteritis can mimic appendicitis and why?
Yersinia enterocolitica
It can invase mesenteric nodes
What organisms can cause dysentery?
Shingella and campylobacter
What does acute gastroenteritis imply?
Diarrhoea for less than 2 weeks
Problems in the large bowel produces a larger or smaller volume of diarrhoea compared to the small bowel?
Smaller volume
What are common problems in the kitchen which lead to gastroenteritis?
Cross contamination of raw and cooked foods Preparation to far in advance Inadequate heating/cooling Contaminated environment Poor personal hygiene
Spores are resistant to most of our cooking methods. T or F?
True
Symptoms of gastroenteritis?
Abdo pain
Vomiting
Diarrhoea.
Caused by invasion of tissue +/- toxin production
Large volume diarrhoea tends to come from the small bowel
What are the mos common organisms in travelers?
Enterotoxigenic E coli
Vibro species
Rota virus
What is the most common organism if the patient has been camping?
Giardia, Aeromonas, Cryptosporidium
What is the most common organism if the patient has had recent antibiotics?
Increased risk of C diff
What is the most common organism if the patient has exposure to see food?
Non cholera Vibro
What is the most common organism if the patient has day care exposure?
Rotavirus
What is the most common organism if the patient has HIV?
Mycobacterium avium- intracellulare complex, CMV, Giadia, Micosporidia
What is the most common organism if the patient is a man having sex with men?
Shingella, campytobacter, salmonella
Outbreak on a cruise ship, whats the organism?
Norovirus
Why do some bacteria have very short incubation times of 1-6 hours?
Due to preformed toxins- the bacteria have not really had enough time to replicate but you ate something with the toxins already there- reheated rice
What is the incubation for bacillus cereus, what type of bacteria is it?
Gram positive bacillus which forms heat resistant spores and a preformed toxin.
Incubation 1-6 hours
What is bacillua cereus associated with?
Reheated starchy foods especially rice.
Profuse vomiting
What is the incubation for staph aureus, what type of bacteria is it?
1-6 hours incubation
Gram positive coccus which develops preformed toxins in food which are rapidly absorbed to act on the vomiting centre in the brain
What is staph aureus gastroenteritis associated with?
Food left out at room temperature
Milk, meat, fish
How does the laboratory identify pathogens from stool samples?
Traditional methods: cheaper, slower, narrower, only live bugs grow, give antibiotic sentitivites but a higher quality specimen is required
Molecular methods: quicker, expensive, no sensitivites, data interpretation ( a positive result does NOT mean that it is the causative organism)
What are all stool samples tested for?
Salmonella, Shingella, Campylobacter, Ecoli0157 and cryptosporidium.
all >4 yrs get C diff too.
You MUST put the clinical details on request
How long does a culture result take?
48 hours
How are bacteria identified by culture?
Selection from the normal bowel flora
Enrichment of small numbers
Genetic methods
Shigella is not common in Scotland. In which organism was the shiga toxin discovered?
Shigella dysenteriae
What does shiga toxin do?
Only produced by shigella.
Binds to receptors found on renal cells, RBCs and in CNS.
Inhibits protein synthesis => cell death
How may types of Shiga toxin are there?
2 where type 2 is more potent than type 1
Shiga- like toxins have been found to be produced by other bacteria. What are the most common?
> 30 serotypes of E coli produce a shigella like toxin
STEC (Shiga like Toxin producing E Coli)
Including E coli 0157
How does STEC cause infection?
Competes with normal bowel flora.
Adheres to the intestinal epithilial cells and elaborate shiga toxin.
Toxins bind to enterocytes in the small and large intestine, enter the cell and irreversibly inhibit protein synthesis => cell death
Shiga toxins can then enter bloodstream via damaged epithilium and cause death to vascular endothilial cells.
Endothilial cell lysis => platelet activation => fibrin disposition and clot and inflammatory cascades.
Microangioplasty propagates distally as the oxins are carried to the kidneys causing HUS and renal failure.
What causes Haemolytic Uraemic syndrome (HUS)?
Shiga like toxins (often from ecoli0157 producing shiga like toxin 2) in the blood.
Microangioplasty propagates distally as the oxins are carried to the kidneys causing HUS and renal failure.
What is Hemolytic-uremic syndrome?
Hemolytic-uremic syndrome (HUS) is a disease characterized by a triad of hemolytic anemia (anemia caused by destruction of red blood cells), acute kidney failure (uremia), and a low platelet count (thrombocytopenia).
What must you do if you diagnose someone with E coli 0157?
Inform public health for contact tracing and investigation.
DO NOT give antibiotics as this propagates haemolytic uraemic sndrome
When should you suspect E coli 0157?
Bloody diarrhoea Food: Beef , raw milk, contaminated water Person to person contact Animal contact Children and elderly at high risk Most cases in under 5s
Who develops Haemolytic uraemic syndrome?
15% of E coli 0157 cases within 2 weeks even though diarrhoea has stopped.
What are the symptoms of Haemolytic ureamic syndrome? Mortality 2%
Abdo pain, fever, palor, petechiae, oliguria.
Bloody diarrhoea
What are the signs of HUS?
High WBC Low platelets Low HB Red cell fragments LDH raised
What investigations should be carried out if you suspect HUS?
Stool culture
U&E, FBC, film, LFT, clotting, urine, lactate dehydrogenase
What should you never give if you suspect HUS?
Antibiotics
Antimotility agents
NSAIDs
When should you notify the health protection unit?
Ecoli 0157
HUS
How is Enterohaemorrhagic E coli (0157 is one serotype) identified in a lab?
McConkey agar.
Antisera for serotypes
DNA of toxin genes
Apart from E coli 0157, what are the other e coli pathotypes and associations?
Entero toxigenic e coli = heat stable toxin, travel related
Entero Pathogenic e coli = no toxin, no invasive, often assymtopatic in non breastfed kids.
EnteroInvasive e coli = watery diarrhoea, invasion, sereny test
Entero Aggregative e coli = travellers diarrhoea, cytogenic, secretogenic, proinflamatory
THESE DO NOT PRODUCE SHIGA LIKE TOXINS
Which types of E coli produce Shiga like toxins?
EHEC = entero Haemorrhagic e coli
What are the characteristics of Campylobacter?
16-24 hour incubation Sporadic, rarely outbreaks, Food: Poultry and raw milk) Small pathogen numbers Most common
When would you give a macrolide antibiotic in Campylobacter?
If you were pretty sure it was Campylobacter with a good history and could rule out EHEC.
In patients who are immunosupressed/very ill.
Still must be aware you may have missed EHEC and antibiotics may propagate HUS.
What is the most common species of Campylobacter?
C Jejuni
Why do we advise that sickle cell patients, those with HIV or Malignancy no to keep reptiles?
Reptiles are full of Salmonella.
With salmonella there is a higher risk of bacteraemia which can seed in these patients
What are the characteristics of salmonella enteritidis?
12-24 hour incubation
Food: poultry meat, raw egg
Produces a toxin and is invasiveD and V, blood, fever
What are the two main branches of salmonella?
Salmonella thyphi and salmonella paratyphi (seen in the UK)
H antigens are found on flagella. T or F?
True
O antigens are found on body of bacteria. T or F?
True
What is typing salmonellae used for?
Obreak investigations. Looks at the different antigens on the body of the salmonellae
What are serogroups useful for?
Pin pointing the source of infection of salmonellae.
Useful in outbreaks and contact tracing
Which groups of salmonella are most common locally?
B, C and D. These serogroups are further divided by looking at H antigens on flagella
Why is listeria monocytogenes know as the fridge organism?
Grows at temperatures between 0 and 4 degrees and is common in people who eat unpasturised foods and preserved meats
What are the characteristics of Listeria monocytogenes gastroenteritis?
Fever, muscle aches and diarrhoea,
9-48 hour incubation
Which patients can present 2-6 weeks following Listeria gastroenteritis with an invasive infection as meningitis or bacteraemia?
Immunosupressed (especially T cell)
Age >50
Pregnant
How is Listeria monocytogenes diagnosed?
Easier from astral site. Blood or CSF. You need to use a specific media if you are culturing from stool
What type of bacteria is listeria monocytogenes?
Gram positive Rod
How is listeria transmitted?
Food, mother to child (can cause death in utero)
What types of immune cells are associated with listeria monocytogenes?
Neutrophils in most people
Also associted with iron overload eg in dialysis
Which organisms are associted with erythema nodosum?
Yersinia, Campylobacter, Salmonella, Shingella
Which organisms are associted with Glomerulonephritis?
Shingella, Campylobacter, Yersinia
Which organisms are associted with Guillian Barre syndrome?
Campylobacter
Which organisms are associted with haemolytic anaemia?
Campylobacter, Yerseinia
Which organisms are associted with HUS?
STEC/EHEC
Shigella dysenteriae
What are the complications of acute diarrhoeal illness?
Bacteraemia, Seizue (children), Chronic diarrhoea (travellers, malabsorbtion), IBS, IBD, Reactive arthritis, HUS, Guillien Barre auto immune disease)
How are most bacterial and all viral gastroenteritus diseases managed?
Supportive. Fluids etc
How is Norovirus and rota virus diagnosed?
Stool sample using PCR
What is the commonest cause of gasterenteritis in children under 3?
Rotavirus.
All children get this before age 5
How is rota virus and norovirus spread?
Person to peron and faecal oral transmission
In which adult individuals can a rota virus infection be severe?
Only in the immunocomprimised. Usually its mild or subclinical
Do you get bloody diarrhoea with rotavirus?
No
How long does rota virus infection last?
1 week
Self limiting
Rota virus effects the absorption and secretion in the bowel, can survive in the environment and has a low infectious dose. T or F?
True
Can you get outbreaks and repeat infections with rota virus?
Yes
repeat infections are milder each time
What is the treatment for rota virus?
Oral rehydration therapy.
IV if very dehydrated
What is the rota virus vaccine and when are babies given it?
Oral live attenuated vaccine which is excreated in faeces. Began in sept 2013.
2 doses given at 2 and 3 months.
What is intussusception and what is the link with the rota virus vaccine?
Intussusception is where a small part of the bowel fold in on itself causing an obstruction. Incidence of this is higher in babies who have had the rota virus vaccine. No dose is given to babies over 24 weeks old
How is norovirus spread?
Person to person
Faecal oral
Droplet
What is the reservoir for norovirus?
Communicirculation. It can survive in the environment on fomites for days, weeks.
Why must you ‘stay away’ from work/school for 48 hours after having norovirus?
Because you get asymptomatic shedding of the viris up to 48 hours post cessation of symptoms.
Where do outbreaks of norovirus occur?
Schools, hospitals, nursing homes
What is the incubation for norovirus and how long does the infection last for?
Incubation is <24 hours and it usually lasts 2-4 days.
Can lead to isolation and cohort nursing
What is One Health?
The idea that antibiotics used in agriculture can effect the pathogens present in humans, whether they are resistant and promoting antibiotic stewardship across the health and agricultural sector. We give animals and plants loads of antibiotics
