Description
Some isolates of Vibrio parahaemolyticus (V. parahaemolyticus) produce two haemolysins: heat-stable direct haemolysin (TDH) and heat-stable direct haemolysin-related haemolysin that is direct heat-stable haemolysin (TRH). The expression of these haemolysins is a virulence factor for the species V. parahaemolyticus. Indeed, they have lytic, cytotoxic and enterotoxic activities. In the natural environment, strains carrying genes encoding haemolysins are rare, while these genes are generally present in strains isolated from the stools of patients suffering from gastroenteritis. Also, searching for pathogenicity by detecting the genes encoding these haemolysins is necessary. A duplex PCR was developed by Kaysner et al 1999 and is applied at the reference centre to assess the pathogenicity of strains of V. parahaemolyticus.
Purpose of the test
- Detection of haemolysins TDH and TRH, virulence factors of V. parahaemolyticus.
- Criteria for performing this test in the context of reference activities.
- Each strain of Vibrio received and confirmed V. parahaemolyticus by the NRC and was isolated from human samples.
Instructions for samples
From a culture of the strain of V. parahaemolyticus to be shipped, prepare a fresh and pure subculture on a nutrient medium and ship one way on an agar plate, or after mass inoculation in depth in a nutrient agar in tube or on a cotton swab in the transport medium after harvesting the subculture.
Instructions for transport
The strain should be packed in a suitable transport medium (agar box or tube, cotton bud with transport medium) and correctly identified.
- Transport in triplicate:
- Well-sealed tins and tubes;
- Packing with adsorbent in secondary packaging (‘transport blister’ type box, plastic trays or zip-lock plastic bag);
- All then placed in a padded envelope or box.
- As soon as possible at room temperature, within 72 hours of preparation
- Labelling and transport conditions in accordance with applicable regulations on infectious material.
- For each strain, the request form (downloadable from the NRCHM website) should be completed in as much detail as possible and attached to each strain sent.
Unacceptable requests
The following criteria are used to reject a sample:
- Unidentified sample,
- Incomplete application form
- Obvious inappropriate storage or transport conditions
- Identification of V. parahaemolyticus not confirmed.
Turn around time (and frequency of analysis)
- Frequency of analysis: On demand.
- Time for detection: 5 working days
- Days of analysis: Every working day from Monday to Friday.
Reporting of test results
- How: telephone communication (1) and paper notification by post (2) or electronic notification (3).
- When: when relevant analysis results are known (even partially) (telephone, e-mail: 1 or 3), when all analysis results are known (written report: 2 or 3).
- Summary of all results available in the annual report.