Rapid detection of viable Salmonella typhimurium in a selective medium by monitoring oxygen consumption with electrochemical cyclic voltammetry

Abstract

A new method for in situ monitoring Salmonella typhimurium in a selective medium was developed by measuring the cathodic peak current of oxygen in cyclic voltammograms during bacterial proliferation with an electrochemical voltammetric analyzer. The rapid oxygen consumption at a time during the growth of bacteria resulted in a sharp decline of the curves. The detection times (threshold values) obtained from the oxygen consumption curve were inversely related to the concentrations of S. typhimurium in the medium. This method for detection of S. typhimurium is more sensitive than nucleic acid-based polymerase chain reaction (PCR) methods and any of the antibody-based methods such as enzyme-linked immunosorbent assay (ELISA) technology, electrochemical immunoassays, immunosensors, and it has a sensitivity similar to conventional culture methods and impedimetric methods but is more rapid than either of them. A calibration curve was obtained by plotting initial cell concentrations (CFU ml −1) determined by conventional plate counting, as a function of the detection time. A linear response was found on the calibration curve for S. typhimurium between 1–2×10 0 and 1–2×10 6 cells per ml. The detection time for 1–2×10 0 and 1–2×10 6 cells per ml of viable S. typhimurium in the medium was 10 and 2.1 h, respectively.