This work describes a rapid and sensitive method for the determination of bacteria. The method is based on an enzyme-taggedimmuno-electrochemical assay. Antibodies are immobilized on disposable carbon felt disc electrodes and are used to capture antigens in test solutions. After a short incubation with a second antibody, which is labeled with the enzyme alkaline phosphatase, the activity of the enzyme electrode thus formed is measured. This enzyme reacts with the substrate p-aminophenyl phosphate and the product of this enzymatic reaction, p-aminophenol, is detected amperometrically. The use of rotating electrodes significantly shortens the incubation times and, together with the computerized electrochemical system, results in extremely high sensitivity. The results obtained with Staphylococcus aereus and Escherichia coli cells show that the system can detect as low as 10 cell/ml in less than 10 minutes.There is a great need for fast and reliable devices capable of detection and identification of various types of bacteria. Traditional microbiological methods are based on cultural techniques which are tedious and slow. A considerable effort has been invested in development of detection methods based on immunological interactions. These methods, which generally involve labeling of antibodies with radioactive, fluorescent or enzymatic label, have been shown to be quite effective, giving specific and quantitative detection of target antigens. During the last decade several attempts were made to combine the specificity of antibody-antigen interaction with the high sensitivity, wide dynamic range, and simplicity of electroanalytical methods. These attempts led to the development of electrochemical immunosensors, several of which detect the corresponding antigen at extremely high sensitivity (1-5).

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