A CHEMILUMINESCENCE BIOSENSOR COUPLED WITH IMMUNOMAGNETIC SEPARATION FOR RAPID DETECTION OF <i>SALMONELLA</i> TYPHIMURIUM

Abstract

A chemiluminescence biosensor, using a fiber‐optic‐linked photometer and a data acquisition unit connected to a PC, was developed in conjunction with immunomagnetic separation for rapid detection of Salmonella Typhimurium. Magnetic microbeads coated with Anti‐Salmonella antibodies and anti‐Salmonella antibodies conjugated with horseradish peroxidase (HRP) were added to artificially‐inoculated samples, and the immuno‐reaction was completed in 60 min resulting in a sandwich complex. A magnetic field was applied to collect magnetic beads and the addition of luminol to HRP‐conjugated antibodies resulted in a chemiluminescence reaction. The signal was collected through a fiber optic light guide, measured with a photometer, and recorded in the data acquisition unit. The minimum detection limit of the chemiluminescence biosensor for S. Typhimurium was 1.97 × 10 3 CFU/mL and the range of the detectable signal was from 8.6 to 350 mV for cell numbers from 1.97 × 10 3 to 1.97 × 10 6 CFU/mL. Signal values for 10 6 CFU/mL of S. Typhimurium were at least 97 and 394% higher than the corresponding values for S. enteritidis and four times the signal values for others including S. montevideo, S. california, S. heidlberg, and S. seftenberg, respectively. The biosensor response showed a significant difference (P &lt; 0.05) between 10 3 CFU/mL S. Typhimurium and 10 6 CFU/mL of commonly‐occurring bacteria in foods including Listeria monocytogenes, Pseudomonas aeruginosa, Citrobacter freundii, Campylobacter jejuni, Escherichia coli O157, and generic Escherichia coli. A regression equation, V = 0.0262 N 5.7713 , with R 2 = 0.9713 was obtained for the calibration curve over the detection range for S. Typhimurium. The whole procedure could be completed within 90 min.