Highly sensitive flow-injection immunoassay system for rapid detection of bacteria

A flow-injection amperometric immunofiltration assay system for the rapid detection of total Escherichia coli and Salmonella was developed. The system is based on the use of disposable porous nylon membranes which act as a support for the immobilization of anti-E. coli or anti-Salmonella antibodies. The assay system consists of a flow-injection system, a disposable filter-membrane and an amperometric sensor. Parameters affecting the performance of the immunofiltration assay system such as membrane pore size, non-specific binding, conjugate concentration and sample volume were studied and optimized. A sandwich scheme of immunoassay was employed and the immunofiltration system was able to specifically and directly detect 50 cells/ml of total E. coli or 50 cells/ml of Salmonella with an overall analysis time of 35 min. This immunosensor can be easily adapted for the assay of other microorganisms and may be a basis for a new class of highly sensitive and automated bioanalytical devices for the rapid quantitative detection of bacteria. (C) 1999 Elsevier Science B.V. All rights reserved.