Vibrio cholerae Culture & Diagnosis

Enrichment Medium
  • Enrichment of the fecal specimens are done on Alkaline peptone water
  • Transported in alkaline peptone water medium
  • Venkatraman Ramakrishnan Meidum is simple medium can be used as transport medium
Culture:
  • 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
  • In resource poor laboratories MacConkey agar can be used.
Selective Medium - TCBS
  • V.cholrae grows well on Thiosulphate citrate bile sucrose (TCBS ) agar, on which it produces large yellow colonies that are readily visible against the dark green background of the agar.
Growth Characteristics
  • 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
ISOLATION OF VIBRIO CHOLERA:
Stool Examination
  • Stool specimen appear as Rice water
  • On Microscopy contain Mucus, epithelial cells and large number of Vibrio's.
  • Milder cases difficult to differentiate from other diarrheal diseases.
  • El Tor vibrio's cause milder disease than classic biotypes.
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.
  • Specimens should not be collected from bed pans.
  • Vomitus not advised.
Diagnosis:
  1. Stool culture: Toxigenic Vibrio cholerae O1
  2. Use Cary Blair Transport media if available
  • Viable for many days at room temperature
  1. Use TCBS media for culture
  2. Use V. cholerae serogroup O1 antisera
  3. Confirm presence of cholera toxin
  4. Cholera Rapid Test Dipsticks
  5. Confirmatory Tests for V.cholerae:
  • V.cholerae organisms are further identified by slide agglutination tests using anti -0 group 1 or group 139 Antisera and by Biochemical reactions
Laboratory Diagnosis:
  • Mucus flecks from stool are cultured.
  • Smears are not useful for diagnosis.
  • Dark field microscopy shows rapidly motile vibrio's.
  • Laboratory Diagnosis Culture:
  • Growth is rapid on Blood agar,
  • On TCBS medium typical colonies can be picked in 18 hours.
  • The stool specimens can be transported in Venkataraman Ramakrishnan medium
  • Alkaline peptone water is ideal enrichment medium
Bio Chemical Reactions:
Characteristic V.cholerae( Classical ) V.cholerae,(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
  • TCBS medium- Thiosulfate, Citrate, Bile salt & Sucrose is the Selective media for Vibrio cholerae
  • Vibrio cholerae Transported in alkaline peptone water
  • Transport medium for stools samples in cholera is Cary Blair medium
  • The cholera vibrio Has marked tolerance of alkaline pH
  • Venkataraman Ramakrishan Meidum is simple medium can be used as transport medium
  • Enrichment media for cholera Alkaline peptone water medium
  • Optimal percentage of NaCl for V cholerae 1%
  • Quarantine period of cholera 5 days
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