Infectious Causes of Gastroenteritis 1 Flashcards
Why is diarrhoea deadly?
Acutely because of loss of fluid and electrolytes and delayed because of malnutrition
Why does diarrhoea cause malnutrition?
because of increased energy loss and reduced energy intake
How much fluid enters the gut per day?
10L
How much fluid is absorbed by the gut per day?
9.9L
What type of diarrhoea does a problem with the small intestine cause?
Infrequent stools with a large watery volume
What type of diarrhoea does a problem with the large intestine cause?
Frequent stools of lowish volume - possibly containing blood and mucus
What is the most common aetiological agent of diarrhoea in developing countries?
Bacteria
What is the most common aetiological agent of diarrhoea in developed countries?
Viruses
What are the aetiological agents of non-specific gastro?
viruses, bacteria, protozoa
What is dystentery?
Diarrhoea with blood and mucus
What are the aetiological agents of dysentery?
shigella, EIEC, protozoa
What are the aetiological agents of food borne diarrhoea?
staph, salmonella, clostridium, bacillus, vibrio, listeria, viruses, ciguatoxin
What are the aetiological agents of travellers diarrhoea?
ETEC, bacteria, viruses, protozoa
What are the aetiological agents of antibiotic associated colitis?
clostridium difficile
What are the aetiological agents of haemorrhagic colitis?
EHEC
What are the aetiological agents of cholera-like diarrhoea (severe and watery)?
vibrio cholerae, ETEC
What are the aetiological agents of enteric fever (typhoid and paratyphoid)?
salmonella typhi, s. paratyphi
What are the 5 different types of diarrhoeagenic E. coli?
enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enterohaemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAEC)
What is the shared adhesin for EPEC and EHEC?
intimin
What is the defining factor of EHEC?
produces shiga toxins
How do some EAEC get the ability to produce shiga toxins?
Because shiga toxins are encoded by bacteriophages
What is the symptom of ETEC?
watery diarrhoea
What is the symptom of EPEC?
non-specific gastro
What is the symptom of EHEC?
blood diarrhoea
What is the symptom of EIEC?
dysentery
What is the symptom of EAEC?
water diarrhoea
Where is ETEC most common?
Infants in developing countries and travellers
Where is EPEC most common?
children in developing countries
Where is EHEC most common?
developed countries
Where is EIEC most common?
developing countries
Where is EAEC most common?
children in developing countries
Which diarrhoea causing bacteria is adhesive enterotoxigenic?
cholera, ETEC
Which diarrhoea causing bacteria is adhesive with brush border damage?
EPEC
Which diarrhoea causing bacteria is restricted to the mucosa?
shigella
Which diarrhoea causing bacteria invades the submucosa?
salmonella, campylobacter
Which diarrhoea causing bacteria can have systemic invasion?
salmonella
How does EPEC adhere to microvilli?
Via bundle forming pili
What is a pathogenicity island?
A block of genes found in pathogens that is missing from non pathogens of the same species
What is the locus for enterocyte effacement (LEE) pathogenicity island?
the locus on EPEC (and EHEC) that determines is pathogenicity - includes type III secretion system, Tir and intimin and effector proteins
What is intimin?
A large outer membrane protein required for intimate adherence between bacteria and the cell
What is Tir?
The receptor for intimin - which human cells don’t express but is carried by EPEC
What is the type III secretion system?
A system which makes up a ‘needle’ to secrete proteins directly into the cytoplasm of the cell
What determines virulence?
adhesins, invasive ability, exotoxins and ability to resist killing
What is an example of a cytotonic exotoxin?
cholera toxin
What is an example of cytotoxic exotoxin?
shiga toxin
Which species of shigella produces shiga toxin?
Shigella dysenteria
What is the mechanism of shiga toxin?
it inhibits protein synthesis
What is dysentery?
Diarrhoea with blood and mucus
What causes dysentery?
shigella dysenteria and EIEC
What can shiga toxin cause?
haemolytic uremic syndrome
Which bacteria have a shiga toxin?
shigella dysenteria and EHEC and EAEC if obtain it through a bacteriophage
