Vibrio cholerae Culture & Diagnosis
Media
- Grow well on ordinary media
- In resource poor laboratories MacConkey agar can be used.
Holding and transport Media:
- VR medium(Venkataraman Ramakrishan Medum)
- Carry-Blair medium
- Autoclaved sea water
Enrichment Medium
- Alkaline peptone water
- Monsour’s taurocholate tellurite peptone water
- Transported in alkaline peptone water medium
Plating media
- Alkaline bile salt agar
- Monsour’s gelatin taurocholate tellurite agar(GTTA)
- TCBS
- V.cholrae grows well on Thiosulphate citrate bile sucrose (TCBS ) agar
- Produces large yellow colonies that are readily visible against the dark green background of the agar.
Growth Characteristics
- V.cholrae produces convex, smooth, round colonies that are opaque and granular in transmitted light;
- Grow well at 370c on many defined media.
- Vibrio’s grow at a very high pH ( 8-5 – 9-5 ) and are rapidly killed by acid
- V.cholerae ferments sucrose and mannose but not arabinose
- A positive Oxidase test is key step in preliminary identification of V.cholerae and other Vibrio’s
- Vibrio species are susceptible to compound 0/129 and differentiates from Aeromonas
- Vibrio’s usually grow on medium containing 1% Nacl
- Halophilic vibrios need and grow in the presence of > 6% Nacl
- On Blood agar Vibrios show hemodigesion
- Quarantine period of cholera 5 days
DIAGNOSIS
Stool Examination
- Stool specimen appear as Rice water
Specimen Collections
- Stool specimens are collected in acute stage of the disease. before the antibiotics are administered.
- Simple collection of stool in a wide Mouthed container is safe and hygienic.
Transport:
- Stool culture:
- Use Cary Blair Transport media if available
- Use TCBS media for culture
Characterstics
- Mucus flecks from stool are cultured.
- Smears are not useful for diagnosis.
- Dark field microscopy shows rapidly motile vibrio’s.
- Motility is inhibited by antiserum.
Serological Examination
- Use V. cholerae serogroup O1 antisera
- Confirm presence of cholera toxin
- Cholera Rapid Test Dipsticks
Confirmatory Tests for V.cholrae:
- V.cholrae organisms are further identified by slide agglutination tests using anti -0 group 1 or group 139 Antisera and by Biochemical reactions
Bio Chemical Reactions:
- Catalase +ve
- Oxidase +ve
- Indole +ve
- Nitrates reduced to Nitrites
- Surcose fermenter
Last two reaction account for cholera red reaction
| Characterstic | V.cholrae( Classical ) |
V.cholrae (El Tor) |
| Hemolysis | -ve | +ve |
| Voges -proskauer test |
-ve |
+ve |
| Polymyxin sensitivity | +ve | -ve |
| Group IV phage Susceptibility | +ve | -ve |
| Chick erythrocyte Agglutination | -ve | +ve |
Exam Question
Holding and transport Media:
- VR medium(Venkataraman Ramakrishan Medum)
- Carry-Blair medium
- Autoclaved sea water
- Transported in alkaline peptone water medium
Plating media
- TCBS
- V.cholrae grows well on Thiosulphate citrate bile sucrose (TCBS ) agar
Growth Characteristics
- Vibrio’s grow at a very high pH ( 8-5 – 9-5 ) and are rapidly killed by acid
- Quarantine period of cholera 5 days
DIAGNOSIS
Stool Examination
Specimen Collections
- Stool specimens are collected in acute stage of the disease. before the antibiotics are administered.
Transport:
- Stool culture:
- Use Cary Blair Transport media if available for transport.
- Use TCBS media for culture
Characteristics
- Mucus flecks from stool are cultured.
- Smears are not useful for diagnosis.
- Dark field microscopy shows rapidly motile vibrio’s.
- Motility is inhibited by antiserum.
Serological Examination
Confirmatory Tests for V.cholrae:
- V.cholrae organisms are further identified by slide agglutination tests using anti -0 group 1 or group 139 Antisera and by Biochemical reactions
Bio Chemical Reactions:
- Catalase +ve
- Oxidase +ve
- Indole +ve
- Nitrates reduced to Nitrites
- Surcose fermenter
| Characterstic | V.cholrae( Classical ) |
V.cholrae (El Tor) |
| Hemolysis | -ve | +ve |
| Voges -proskauer test |
-ve |
+ve |
| Polymyxin sensitivity | +ve | -ve |
| Group IV phage Susceptibility | +ve | -ve |
| Chick erythrocyte Agglutination | -ve | +ve |
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