Lecture 5 Flashcards
What is diarrhoea and what causes it?
Diarrhoea is a condition characterized by frequent, loose, and watery stools. It results from an imbalance of absorption and secretion of ions and solute across the gut epithelium, followed by the movement of water in an attempt to restore the appropriate ion concentrations.
How do toxins trigger diarrhoea?
Toxins typically trigger signalling molecules such as cyclic AMP or intracellular Ca 2+ which in turn activate cellular Cl channels leading to increased Cl secretion and subsequently water secretion.
What are STEC and ETEC, and where are they commonly found?
STEC (shiga toxin producing) and ETEC (enterotoxigenic) are the most common bacteria that cause diarrhoea in water and food.
What is the primary host of EPEC, and when do outbreaks occur?
Humans are the primary host of EPEC, and outbreaks occur when children are in close contact.
What are the diagnostic criteria for EPEC?
EPEC is diagnosed by serotyping mainly based on O Antigen, attaching and effacing lesion (A/E), fluorescent actin stain, tyrosine phosphorylation at the site of infection, and localized adherence.
Where do EHEC (STEC) originate from?
EHEC (STEC) originates from animals, especially ruminants.
What is ETEC, and what are its characteristics?
ETEC is a common cause of traveller’s diarrhoea, which usually lasts 3-5 days. It can appear as ST (heat stable toxins) or LT (heat labile toxins) form.
What do the ST and LT forms of ETEC do?
The ST form elevates cGMP levels, inhibits NaCl absorption, and stimulates chloride secretion. The LT form activity increases cAMP levels.
What is shigellosis?
Shigellosis is a condition characterized by the destruction of colonic epithelium provoked by the inflammatory response induced upon invasion of the mucosa by bacteria
Pathogenesis of shigellosis
Bacteria enter M cells and are delivered to resident macrophages, in which they induce apoptosis.
The bacteria reach the basolateral pole of epithelial cells.
The bacteria enter epithelial cells.
There is movement of intracellular bacteria.
Formation of protrusions and dissemination of bacteria within the epithelium.
Release of cytokines and chemokines, including IL-1 by apoptotic macrophages and IL-8, promotes recruitment of monocytes that migrate through the epithelial barrier, facilitating entry of luminal bacteria into epithelial cells and invasion of the epithelium.
What is Vibrio cholera and its serotypes?
Curved gram negative bacilli. It produces two serotypes that cause disease O1 and O139.
What is the main reservoir for vibrio cholera?
Human is the main cholera reservoir, but it may contaminate water and shellfish.
What does C. jejuni infect, and how is it transmitted?
C. jejuni infects the intestinal tract of several animal species, including chickens, cattle, and sheep. The organism is transmitted in milk and meat products.
What serotype is salmonellosis most commonly caused by and how is it transmitted?
Salmonellosis is the common salmonella infection caused by a variety of serotypes, most commonly S. enterica, and is transmitted from contaminated food, such as poultry and eggs.
Symptoms of salmonellosis
It presents as a gastroenteritis (nausea, vomiting, and non-bloody stools). The disease is usually self-limiting (2-5 days).
