BIOL334 Lecture 4- Cholera Flashcards
(25 cards)
Is Vibrio cholera invasive?
No. The disease occurs at the mucosal surface with no invasion by the microbe into deeper tissues.
What is the infective dose of cholera?
- 1 molecule (the cholera toxin is delivered through the cell wall).
Cholera cases 1986-2016
- Proportions change based on location.
- In Americas relatively calm for 20-30 years but then a surge occurred in 2011.
- Due to changes in infrastructure environment and us allowing cholera into the human population.
- Northern Hemisphere largely exempt.
- Asia, Africa and South America are usually affected
Who was Pacini and what did he do?
Pacini- From Florence, Italy
- 1854 discovered vibrio cholera but ignored due to presence of miasma (bad air) theory.
Who was Koch and what did he discover?
- Koch has greater pre eminence
- Rediscovered V.cholerae bacterium but didn’t prove it
- Wasn’t aware of Pacinis work
V. cholera physiology
- Facultative anaerobe
- Gram negative (thinner peptidoglycan)
- Rod shaped
- Asporogenous
- Growth stimulated by Na Cl
- Temp 18-37 degrees
- Can enter VBNC state
What is a serotype of cholera?
- Differences in the sugar composition of heat stable surface O antigen.
Which serotypes cause Cholera outbreaks
- Serotype O139- first identified in Bangladesh and is confined to SE Asia.
- O1 causes majority
What can you further breakdown serotypes into
- Ribotypes
- This allows precise identification of what is causing an outbreak
Why is V.cholerae considered a true environmental pathogen?
- Found in coastal waters and estuaries (warm coastal waters Bangladesh, Asia and India).
- Often associated with zooplankton
- It can use chitin (part of exoskeleton) as a carbon and nitrogen source
- Can secrete chitinase- nutrient source?
- Goes up the food chain and spreads
What causes the seasonality of Cholera?
- Agal blooms in warmer temperatures
- Zooplankton follow algal bloom patterns
- V. cholera are associated with zooplankton
- Al three increase with each other
Pathogenicity of V. cholerae
- 2 chromosomes
- Chromosome 1- house keeping genes and VPI attachment pills, CTx toxin
- Chromosome 2- integral islands (area of hotspots which you can accumulate drug resistance etc).
Virulence factors of V. cholerae
- Adherence: Accessory Colonisation Factor- sticks to surfaces of sI.
- Motility- flagella- The flagellar regulatory system positively regulates transcription of a diguanylate cyclase that regulates transcription of haemaglutinin–> intestinal colonisation
- Binding of haemaglutinin to YcgR gene allows biofilm formation by switching of flagella.
The importance of Quorum Sensing in Cholera infection
- Vibrio cholerae (V. cholerae) is a human pathogen that utilizes quorum sensing to colonize a host and produce its toxin.
- QS pathways regulate timings of production of colonisation factors and toxins
- At least 4 sensory inputs function in parallel to regulate QS.
- Relies on secretion and detection of signalling molecules (autoinducers or AIs).
- Low cell density= expression of virulence factors (toxin) and biofilm formation
- High cell density= accumulation of 2 QS HIs repress these traits
How does V.cholerae cause infection?
- Secrete enterotoxin (Stx)
- Enterotoxin binds to intestinal cells
- Chloride channels activated
- Release large quantities of electrolytes and bicarbonates
- Fluid hyper secretion
- Diahorrea
- Dehydration
Vibrio cholerae virulence
- The genes for Ctx toxin are carried by CTX phage. The temperate bacteriophage is inserted into the V.cholerae genome.
- CTX phage can transmit cholera toxin genes from one V. cholerae to another
Symptoms of cholera
profuse watery diarrhea, sometimes described as “rice-water stools” vomiting. thirst. leg cramps. restlessness or irritability.
What is transduction
occurs when foreign DNA or RNA is introduced into bacterial or eukaryotic cell via a virus or viral vector
What is Transformation
- Uptake of genetic material from the environment by bacterial cells
- This comes from adjacent lysed bacteria and can include plasmid DNA or fragmented DNA released into the environment
What is Conjugation
- Genetic material is transferred from a donor bacterium to a recipient bacterium through direct contact
- The donor bacterium has a DNA sequence called a fertility factor (F factor).
- F factor allows a sex pilus to form that attaches to recipient cell
- Once in close contact the donor can transfer genetic material to recipient
Methods for cure for cholera
- Chemotherapeutic: Antibiotics (tetracycline)
- Immunological: Mucosal immune response, serological anti-vibrio antibodies, antitoxin antibodies
- Oral rehydration to ease symptoms, intravenous rehydration
Management strategies for Cholera
- Cholera cots- 7 inch hole in beds for patients that can’t walk, proper disposal prevents cross contamination.
- Filtration: cloth of old sari folded 4 times to filter zooplankton bearing cholerae. Villages that did this had a 48% reduction in cholera compared to those that didn’t.
- Education: sanitation, personal and domestic hygeine
- Prevention of contamination of water supplies- hygienic disposal of human waste, improvement of sewage systems.
- Good food hygeine, washing hands after defecation and before cooking.
- Mapping and data: focusing on high incidence area first, targeted interventions could eliminated 50% of the regions cholera in Sub Saharan Africa
Haiti Cholera Epidemic
- Jan 2010
- Began in October 2010
- Killed 5000 people
- By the first 10 weeks cholera spread to all 10 provinces
- by 2018- 820,000 cases.
- Major source: UN relief workers
Where is there currently a Cholera crisis?
Yemen 2016-2020 ~4000 deaths
- due to infrastructure breakdown, bombing, war, sanitation, sewers
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