ENZYME-LINKED IMMUNOMAGNETIC ELECTROCHEMICAL DETECTION OF SALMONELLA-TYPHIMURIUM

There is a need for rapid methods to detect pathogenic bacteria in foo d products as alternatives to the current laborious and time-consuming culture procedures. We report a microbial detection technique that co mbines the selectivity of antibody-coated superparamagnetic beads with the rapidity and sensitivity of electrochemical detection in a format termed enzyme-linked immunomagnetic electrochemistry. In it, Salmonel la typhimurium were sandwiched between antibody-coated magnetic beads and an enzyme-conjugated antibody. With the aid of a magnet, the beads (with or without bound bacteria) were localized onto the surface of d isposable graphite ink electrodes in a multi-well plate format. Enzyme substrate was added and conversion of substrate to an electroactive p roduct was measured using electrochemical detection. The electrochemic al response was directly proportional to the number of captured bacter ia. Using this technique, a minimum detectable level of 8 x 10(3) cell s/ml of Salmonella typhimurium in buffer was achieved in ca. 80 min.