Quantum dots as fluorescent labels for quantitative detection of Salmonella typhimurium in chicken carcass wash water.

Fluorescent semiconductor quantum dots have recently emerged as a novel and promising class of fluorescent labels for biological detection. In this study, quantum dots were used as fluorescent labels in immunoassays for quantitative detection of foodborne pathogenic bacteria. Salmonella Typhimurium cells were separated from chicken carcass wash water using anti-Salmonella antibody coated magnetic beads and reacted to secondary biotin-labeled anti-Salmonella antibody. Quantum dots coated with streptavidin were added to react with biotin on the secondary antibody. Measurement of the intensity of fluorescence produced by quantum dots provided a quantitative method for microbial detection. A linear relationship between Salmonella Typhimurium cell number (log N) in the samples of chicken carcass wash water and the fluorescence intensity (FI) was found for the cell numbers ranging from 10(3) to 10(7) CFU/ml. The regression model can be expressed as FI = 198.6 Log N - 639.03 with R2 = 0.96. The detection limit of this method was 10(3) CFU/ml.