Lecture 8: Enteric Pathogens Flashcards
Includes focus on C. Botulism and Salmonella enterica
Attachment and adherence are not the same thing. Distinguish between these two terms.
Attachment is non-specific weak binding, adherence is an active process involving ligand-receptor interaction that are very strong.
What are enteropathogens?
Microorganisms that cause disease relating to or occurring in the intestines.
What common examples of bacteria that cause GI disease by toxins only that I should know?
- Staphylococcus Aureus
- *Clostridium Spp. *(Spp. means superspecies - multiple species).
What percentage of deaths in under 5’s do diarrheal diseases account for?
0.18%
Why shouldn’t children under the age of 1 eat honey?
Honey can contain C. botulism spores that cause infant botulism.
How can botulism be treated?
With antitoxins, which are antibodies that neutralise the toxins.
Why is Clostridium botulinum difficult to eliminate from food?
It produces heat-resistant spores that can survive normal cooking temperatures.
How can Clostridium botulinum spores be destroyed?
Heating to 120°C for 5 minutes.
What type of bacteria is Clostridium botulinum, what environment does it require to grow and what type of toxins does it produce?
Gram-positive rod-shaped bacteria, obligate anaerobe, heat-labile neurotoxins.
How do Botulinum Neurotxins cause intestinal paralysis?
Toxin is taken into neurone by endocytosis. It interferes with action of acetylcholine by destroying acetcholine docking site for exocytosis. Acetylcholine is not released into the synaptic cleft.
How can botulism neurotoxins be used therapeutically?
Paralysis of smooth muscle in patients suffering from urinary incontinence and chronic migraines. Used in beauty industry to reduce wrinkles.
Which two of the six types of pathogenic E. coli do I need to know?
ETEC (Enterotoxigenic E. coli) and EHEC (Enterohaemorrhagic E. coli).
What is the primary treatment for E. coli infections?
Oral rehydration is the main treatment, but severe cases may require IV rehydration.
What is an example of a highly virulent E. coli strain that cannot be treated with antibiotics (bacterial death causing increased release of toxin) and what toxin does it produce?
EHEC O157:H7, which produces Shiga toxin.
What types of antigens are O and H antigens?
O antigens are LPS antigens; H antigens are flageullum antigens.
What toxins does ETEC produce?
Heat-stable enterotoxins (Type 1), Type III AB exotoxins, which are heat-labile.
What is the mode of action of Type III AB exotoxins in ETEC?
They bind to GM1 receptors, leading to an increase in cAMP, which causes an imbalance of electrolytes and water, resulting in diarrhoea.
What is dysentery?
A type of gastroenteritis, inflammatory disorder of gastrointestinal tract, associated with blood and pus in faeces, accompanied by pain, fever, abdominal cramps; usually resulting from invasive infection in large intestine.
How effective are the 2 available vaccines for Salmonella enterica?
70%, booster required every 3 years.
Who can carry Salmonella enterica and what percentage of infected individuals become chronic carriers?
Humans only, 5% of infected individuals become chronic carriers.
What causes chronic carriage of Salmonella enterica?
Persistent infection of the gall bladder.
How does Salmonella enterica invade host cells?
It uses a Type 3 secretion system to enter the host cell cytoplasm. It then reproduces in the vacuole.
What type of bacteria is Salmonella enterica?
Salmonella enterica is a Gram-negative, rod-shaped bacterium. It is a facultative anaerobe.
What is LD50?
The amount of a toxic agent that is sufficient to kill 50% of a population of animals
