Adsorption of endogenous polyphenols relieves the inhibition by fruit juices and fresh produce of immuno-PCR detection of Escherichia coli O157:H7

The immuno-polymerase chain reaction (PCR) approaches facilitate rapid (8 h) detection of Escherichia coli O157:H7 in contaminated dairy products and ground beef samples with detection sensitivities approaching 1 colony forming unit (cfu) g(-1) ml(-1). However, no PCR products were obtained when the method was applied to identify E. coli O157.1-17 in tainted apple juice. Enzyme-linked immune-assay (ELISA) results suggested non-specific binding of endogenous polyphenols (ubiquitous in plant products) to antibodies present on the surface of the immunobeads, making the latter unavailable for capturing the target bacteria. Treatment of the test sample, prior to IMS, with a synthetic fining agent, polyvinylpyrrolidone, restored the full function and sensitivity of the immuno-PCR. The study demonstrates the suitability of the improved method as a generic strategy for rapid screening of fruit juices and plant produce for E. coli O157:H7. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.