A biosensor for Escherichia coli based on a potentiometric alternating biosensing (PAB) transducer

Routinary methods for the detection of bacterial contamination in table water are costly and time consuming. In the present paper we describe a biosensor based on an immunoassay test. Escherichia coli cells present in water samples were detected by a complete Potentiometric alternating biosensor (PAB). The PAB system consists of a measuring chamber, acquisition and driving electronics and the appropriate software: the apparatus is computer controlled in order to obtain on-line acquisitions and recording of data. The transducer principle is based on a LAPS (Light Addressable Potentiometrie Sensor) technology which, in our case, reveals the production of NH3 by a urease-E. coli antibody conjugate. The proposed system appears to be very sensitive: concentrations of 10 cells per mL were clearly detected over blank of E. coli free water. No signals were detected from other bacteria, eventually polluting drinking water such as Pseudomonas marina, and also from bacteria such as Klebsiella oxytoca phyletically related to E. coli.