Artificial Dosing of Bivalve Molluscs with E. Coli for the Testing of Purification Tanks

Summary

In England and Wales the purification of bivalve molluscs in purpose built tanks requires a bacteriological test as part of the approval procedure to demonstrate satisfactory operation. Using the bacteria Eschericia coli (E. coli) as an indicator of faecal pollution, initial high levels in bivalve molluscs placed in a tank must reduce to below prescribed levels within 42 hours. Problems with obtaining naturally or artificially contaminated bivalve molluscs with sufficiently high levels of E. coli have resulted at times in considerable cost and inconvenience. The main problem with artificial dosing being the unpredictability associated with attempting to dose all bivalve molluscs in the purification tank at once. MAFF and Seafish considered that a new approach might be to dose only a small quantity in a separate tank and place these molluscs at defined sampling points in the purification tank instead. Trials were first conducted by MAFF at their Weymouth Laboratory with the use of freeze dried ampoules containing a know titre of E. coli to dose bivalve molluscs in a small portable purification tank developed by Seafish. By using this tank it was possible to control tank operating conditions and therefore have more control over the uptake of E. coli by bivalve molluscs immersed in it. The results for mussels were reasonably consistent, with more variability shown with oysters. Nevertheless it was shown that these species could be dosed to the required levels. A standard protocol was, therefore, developed for artificial dosing using this technique. This report has been produced from a scanned original and may therefore contain some formatting and other inaccuracies. In cases where this affects the technical content, a paper copy of the original report can still be obtained from Seafish.

Publication Reference No.

SR413

Publication date

01 February 1992