Determination of serogroup and serotype for Vibrio Cholerae

Description of the test

• Serogroups O1 (classical and El Tor biotypes) and O139 are the major pathogens in cholera epidemics. Serogroup O1 strains are classified into three serotypes (Ogawa, Inaba and Hikojima) and are responsible for most cases of cholera.
• The serogroup is determined by serum agglutination of the Vibrio cholerae strains with the anti-O1 and anti-O139. The agglutination tests of V. cholerae O1 strains with other antisera allows the differentiation of V. cholerae O1 serotype Inaba, V. cholerae O1 serotype Ogawa and V. cholerae O1 serotype Hikojima.

Purpose of the test

• Characterisation of the serogroup and serotype of all V. cholerae strains
• Criteria for performing this test in the context of reference activities.
• All Vibrio strains received and confirmed as V. cholerae by the NRC and isolated from clinical samples.

Instructions for samples

Starting culture of V. cholerae strain from a fresh and pure subculture on a nutrient agar medium and sent either on agar plate, deeply and mass inoculated in a nutrient agar tube, or on a swab in transport medium after scraping a subculture.

Instructions for transport

The strain should be sent on the appropriate transport medium (agar plate, agar tube or swab with transport medium) and correctly labelled.

• Transport in triple packaging:
• agar plates and tubes hermetically tightly closed;
• packaging with adsorbent material in secondary packaging (Transport case in blister pack, containers, etc.).
• the whole in a protective (padded) envelope or box.
• As soon as possible at room temperature, within 72 hours of preparation.
• Labelling and transport conditions in accordance with infectious agent regulations.
• For each strain, the application form (download on Sciensano’s NRC website) should be completed as fully as possible and sent with the strain.

Unacceptable requests

The following criteria are used to not accept the sample for analysis:

• unidentified sample
• application form incompletely completed,
• obvious conditions for storage and transport not applied
• identification of V.cholerae not confirmed.

Turn around time (and frequency of analysis)

• Frequency-of analysis: at request.
• Time required for analysis: 48 hours.
• Days of analysis: every working day from Monday to Friday.

Reporting of test results

• How: reporting by phone (1), paper by mail (2) or electronically (3).
• When: if (even partial) relevant results of analyses are known (telephone, e-mail: 1 or 3), if all results of analyses are known (written report 2 or 3)
• Summary of all results available in the annual report