6.3.2 Cholera and Vibrio cholerae Flashcards
(24 cards)
what is the causative agent of cholera
Vibrio cholerae
how is Cholera acquired
primarily through contaminated water
Cholera cots
- a hole is present in the cot to accommodate excessively fatigued and weakened patients
- there is a bucket under hole to collect ‘rice stool’
what is rice stool
a cloudy type of diarrhea that is the hallmark for this infection
diarrhea results in massive loss of..
water and ion imbalance in host – causes severe dehydration and rapid organ failure
treatment for cholera
equal volumes of intravenous or oral rehydration therapy
disposal of diarrhea
bleach to kill bacteria
- disposed in inactive but dirt sewage
Vibrio cholera facts (type of shape, bacteria…)
Vibrio shaped (comma), is gram negative
in some cases Vibrio cholerae can form biofilms – how?
group of bacteria attached to chitin surfaces by secreted protein GbpA
the bacteria degrades chtin..
uses that carbon source for survival in environment
GbpA
secreted by bacterium and then externally sticks to bacterial cell surface to facilitate attachment - binds to bacteria and enterocytes
Attachment to host cell - steps
- Vibrio cholerae uses GbpA again to colonize the epithelial lining of the small intestine (biofilm is formed)
- the mucus layer covering intestinal lining is hydrolyzed by sialidase and reveals receptor for the cholera toxin (GM1)
with attachment and biofilm production on epithelial cell, what is now produced
cholera toxin (AB5), toxin co-regulated pilus (TCP) is also produced
- pilus mediated strong attachment to the epithelial cells, while cholera toxin is produced and secreted from those cells
how cholera toxin gains entry into cell
cholera toxin binds to GM1 receptor on the surface of eneterocytes and uses that receptor to gain entry.
when AB5 enters cell what happens
A subunit is released – hyperactivates adenylate cyclase – results in specific ion imbalance
– chloride ions ar epumped out of cell followed by water
at the ion imbalanced stage, what happens to the bacteria on the enterocytes
toxin is no longer synthesized, co-reg pili are also no longer synthesized, and the bacterial cells are now loosely attached to the shrinking, dying, enterocytes (from the loss of water).
what is the role of HapA
degrades mucin and GbpA
– cholerae cells detach from the enterocytes, penetrate through the fluid filled lumen, and prepare to enter aquatic environment.
what are the three Vibrio cholerae genetics
Bacteriophage CTX, Environmental signals, TCP and Cholera toxin genes.
Bacteriophage CTX
- genes encoding the cholera toxin are encoded in bacteriophage.
- lysogenic
- pathogenic strains of Vibrio cholerae result from horizontal gene transfer (transduction)
Environmental signals (TCP and Cholera toxin)
are expressed when biofilms have formed in intestine (signal)
Environmental signals (sialidase)
expressed AFTER biofilm formation, when needed to degrade mucus
environment signals (HapA)
degrades proteins to acquire nutrients, and to facilitate release of bacteria from dying cells
TCP and Cholera toxin gene expression is regulated by..
a single transcription factor
this single positive regulator is used to turn on two of the bacterium’s most dangerous weapons
the pilus to attach to host – attachment will allow colonization
cholera toxin expression that will damage the host, and cause massive diarrhea
