The detection of Cryptosporidium parvum and Escherichia coli O157 in UK bivalve shellfish

Optimised immunomagnetic separation methods to detect Cryptosporidium parvum and Escherichia coli O157 in UK shellfish are described. Whole tissue homogenates gave the best recoveries for C. parvum oocysts compared with gill or haemolymph extracts. The sensitivity of recovery from spiked samples was comparable to that achieved when processing water and varied from 12-34% in mussels, 48-69.5% in oysters and 30-65% in scallops. Maximum recovery of E. coli O157 was achieved by enriching in buffered peptone water supplemented with vancomycin at 42 °C. Increasing enrichment temperatures from 37 to 42 °C gave a significant increase in target number recovery. Implementation of these methods into monitoring programmes and end-product testing will enable shellfish producers to better assess product safety.