Research by the NRL for monitoring bacteriological and viral contamination of bivalve molluscs
Shellfish (clams, oysters) may be contaminated with human pathogenic bacteria and viruses. Bacterial contaminants are mainly belonging to the genus Vibrio, whereas noroviruses and hepatitis A virus dominate as viral contaminants. For reasons of precautionary consumer protection shellfish harvesting areas are, therefore, subject to hygiene control. The germ count of shellfish is measured and they are examined for pathogens. Depending on the outcome of these controls, shellfish are either released for consumption or protective measures have to be carried out. Furthermore, random samples are also taken of shellfish intended for human consumption within the framework of import procedures and the retail trade.
The main area of research of the BfR "National Reference Laboratory for monitoring bacteriological and viral contaminantion of bivalve molluscs" is the development, evaluation and validation of methods for the detection of bacteria and viruses in shellfish.
Research areas:
- For the fast, sensitive and specific detection of humanpathogenic vibrios found in shellfish real-time polymerase chain reaction (PCR) techniques are being adapted for routine testing. Furthermore, for epidemiological studies PCR typing methods are required which permit the discrimination of single isolates of the same species.
- Vibrios often produce toxins of which haemolysins play a prominent role in gastroenteral disorders. Based on immunological methods, tests for haemolysin production shall be developed to allow a risk assessment of foodborne Vibrio isolates as potential human pathogens.
- There are no tissue culture methods for virus detection at the present time as the corresponding viruses cannot yet be cultivated at all or only with great difficulty. For virus detection in food molecular biological methods are to be established and updated in line with the latest scientific findings.
- The preparation of samples for the corresponding molecular biological tests is of particular interest because of the frequently low virus concentration and the presence of inhibitors in shellfish that can impede virus nucleic acid detection using PCR analysis. Various existing methods for nucleic acid extraction are compared and the corresponding methods validated..
- Besides the classical PCR, real-time PCR is becoming established for both hepatitis A virus and noroviruses. It is being tested in line with its sensitivity and specificity. The enzymes of various suppliers to be used in the PCR are tested by way of comparison for their sensitivity and optimised for use in PCR.
- Comparative tests of the various national laboratories are conducted at regular intervals.
- Weitersagen:
