Podcast
Questions and Answers
What is the characteristic of Vibrio cholerae that enables it to move?
What is the characteristic of Vibrio cholerae that enables it to move?
Polar flagellum
What is the function of thiosulphate citrate bile-salt sucrose agar (TCBS) in laboratory diagnosis?
What is the function of thiosulphate citrate bile-salt sucrose agar (TCBS) in laboratory diagnosis?
To highlight Vibrio cholerae as bright yellow on the agar plate
What is the role of bromothymol blue and thymol blue in the agar?
What is the role of bromothymol blue and thymol blue in the agar?
To act as pH indicators
What is the characteristic of coliforms that allows them to ferment lactose?
What is the characteristic of coliforms that allows them to ferment lactose?
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What is the purpose of the Most Probable Number (MPN) analysis?
What is the purpose of the Most Probable Number (MPN) analysis?
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What is the first step in treating water to make it safe for consumption?
What is the first step in treating water to make it safe for consumption?
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What is the primary function of an indicator organism?
What is the primary function of an indicator organism?
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What is the purpose of the enriched dipstick test in laboratory diagnosis?
What is the purpose of the enriched dipstick test in laboratory diagnosis?
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What is the effect of the enterotoxin released by Vibrio cholerae?
What is the effect of the enterotoxin released by Vibrio cholerae?
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Study Notes
Vibrio cholerae Characteristics
- Gram-negative, highly motile bacterium with a polar flagellum
- Possesses pili, does not form spores
- Oxidase positive, producing cytochrome c oxidase
- Colonizes the epithelium of the small intestine
- Releases enterotoxin, disrupting ion transport and causing diarrhea
Laboratory Diagnosis of Vibrio cholerae
- Enriched dipstick test: color change to pink indicates a positive sample
- Thiosulphate citrate bile-salt sucrose agar (TCBS) with bromothymol blue and thymol blue as pH indicators highlights Vibrio cholerae as bright yellow on the agar plate
Indicator Organisms
- Easily detectable and correlated with pathogen concentration
- Survives easier and longer than the pathogen
- Detection is easy, safe, and inexpensive
- Effective for all water types
Coliforms
- Rod-shaped, Gram-negative, non-spore-forming bacteria
- Motile and non-motile, lactose fermenters, producing gas and acid at 37°C
Water Quality Testing
- Most probable number (MPN) analysis: add reagent to sample, incubate, and read under UV light
- Other tests include membrane filtration, catalase test, oxidase test, and Gram staining
Water Treatment
- Coagulation: add positive salts to neutralize suspended particles, allowing larger particles to settle
- Note: does not remove viruses or bacteria
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