Simultaneous Detection of Salmonella typhimurium and Escherichia coli O157:H7 in Drinking Water with Mach–Zehnder Interferometers Monolithically Integrated on Silicon Chips †

Abstract

The consumption of water contaminated with bacteria can lead to foodborne disease outbreaks. For this reason, the development of rapid and sensitive analytical methods for bacteria detection is of primary importance for public health protection. Here, a miniaturized immunosensor based on Mach–Zehnder Interferometry for the simultaneous, real-time determination of S. typhimurium and E. coli in drinking water is presented. For the assay, mixtures of bacteria solutions with anti-bacteria-specific antibodies were run over the chip, followed by biotinylated anti-species-specific antibody and streptavidin solutions. The assay was fast (10 min), accurate, sensitive (LOD: 3 × 102 cfu/mL for S. typhimurium; 2 × 102 cfu/mL for E. coli) and reproducible. The analytical characteristics achieved combined with the small chip size make the proposed biosensor suitable for on-site bacteria determination in drinking water samples.