28 Questions
What is the most likely causative organism for the patient's symptoms?
Vibrio cholerae
What are the points indicating the cause of the patient's symptoms?
Shellfish, watery diarrhea, and dehydration
Describe the culture in Thiosulphate-citrate-bile-sucrose (TCBS) media.
Yellow colonies
What is the pathogenesis of Vibrio cholerae?
Secretion of enterotoxin (cholera toxin)
Describe the microbiological characteristics of Vibrio cholerae.
Gram-negative, curved or comma-shaped rods/bacilli
How do we treat Vibrio cholerae infection?
Mainly by rehydration; antibiotics in severe cases
What are the clinical features of Vibrio cholerae infection?
Vomiting, watery diarrhea, abdominal cramps
Which statement about Vibrio cholerae is FALSE?
Gram-positive
Which symptom is NOT typically associated with cholera gravis?
Fever
Which medium is NOT used to differentiate the colonies of Vibrio cholerae?
MacConkey agar
What is the approximate annual number of deaths caused by cholera?
100,000
Which strain of cholera has a higher infection rate?
El Tor strain
In which regions do the majority of cholera cases occur?
India, Sub-Saharan Africa, Southern Asia
What is the primary mode of transmission of cholera?
Contaminated water and food
Who is at a higher risk of contracting cholera?
Individuals with less gastric acidity
What is the approximate daily volume of infectious material produced by an infected person?
1,000,000 bacteria
What is the main source of infection for cholera?
Human feces
What did John Snow's discovery in London in 1854 reveal about cholera?
It was related to contaminated water supply
What is the shape of Vibrio Cholerae?
Comma-shaped
Which characteristic helps prevent cholera?
Good sanitation system
Which serogroup organisms are the causes of epidemic cholera?
V. cholera O1 and O139 only
Where is V. cholera O139 contained?
India and Bangladesh
What did the removal of the pump handle lead to in London in 1854?
Decrease in waterborne diseases
What is the shape of Vibrio cholerae?
Rod-shaped
Which of the following is NOT a symptom of cholera gravis?
Hypoglycemia
Which medium is used to differentiate the colonies of Vibrio cholerae?
Thiosulphate-citrate-bile-sucrose
What is the primary mode of transmission of cholera?
Fecal-oral transmission
What are the clinical features of Vibrio cholerae infection?
Vomiting, watery diarrhea, abdominal cramps
Study Notes
- Cholera causes 1-3 million cases and 100,000 deaths each year, with a contagion period of one to three weeks. Dates back to 1817, with Classical strain having a lower infection rate (1 case per 30-100) and El Tor strain having a higher infection rate (1 case per 2-4).
- Endemic in over 50 countries, with majority of cases occurring in India, Sub-Saharan Africa, and Southern Asia. Transmission is primarily through contaminated water and food, especially in areas without well-established sewage systems and water treatment.
- Children, elderly, and those with less gastric acidity are at higher risk of contracting cholera. Infected persons can produce up to 20 L of 10⁹ CFU/ml/day and have a high infectious dose (10⁶-10¹¹ CFU).
- Cholera is characterized by a wide range of clinical manifestations, from mild or no symptoms to severe disease. Symptoms include frequent, watery diarrhea, vomiting, cramps, dehydration, and rapid loss of body weight.
- Cholera results from secretory diarrhea caused by the actions of cholera toxin (CT) on intestinal epithelial cells. CT is an adenosine diphosphate-ribosylating enzyme that leads to chloride, sodium, and water loss from the intestines.
- Cholera toxin binds to Monosialoganglioside (GM1) on epithelial cells, undergoes cleavage, and activates the Gs protein, leading to the elevation of intracellular cyclic adenosine monophosphate (cAMP) concentration and subsequent loss of water and electrolytes.
- Untreated cholera can result in dehydration, shock, hypoglycemia, cardiac and renal failure, aspiration pneumonia, and death within hours to a few days, depending on the infectious dose and gastric acidity.
- Risk factors for cholera include living in areas with poor sanitation and water treatment, taking antacids, and having a lower infectious dose due to the body's inability to produce sufficient gastric acid.
- Cholera is primarily found in developing and war-torn countries due to poor water and sanitation conditions, as well as weak healthcare systems.
- Cholera can be treated with antibiotics (such as doxycycline) and fluids to prevent infection and alleviate symptoms. If intravenous fluids are not available, mortality rates are higher.
- Cholera vaccines are available, with two main types: a dead vaccine with less immunogenicity and a live attenuated vaccine with longer immunity. These vaccines are recommended for people traveling to endemic regions and those exposed to the pathogen.
- Cholera is a type B acute watery diarrhea caused by the bacterium Vibrio cholerae, transmitted through contaminated water and food. It is characterized by a sudden onset of watery diarrhea and vomiting and is most susceptible to individuals with blood type O.
- A watery stool sample collected from a 5-year-old boy who has been suffering from diarrhea for two days yielded smooth and round colonies in high pH media containing NaCl, which were identified as Gram-negative, motile, comma-shaped bacteria, consistent with Vibrio cholerae.
Test your knowledge of cholera microbiology with this quiz. Recall the epidemiology, microbiological characteristics, pathogenesis, clinical features, laboratory diagnosis, management, and control of cholera outbreaks.
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