BIOL334 Lecture 4- Cholera Flashcards
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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