Nanogold based lateral flow assay for the detection of Salmonella typhi in environmental water samples

Abstract

Background: Salmonella infection is one of the leading causes of water and food borne diseases and is the cause of approximately 3.5–18 million deaths per year worldwide. The severity of this infection demands the early detection of bacteria in drinking water before its consumption. The present study, therefore, attempts to develop a rapid lateral flow assay for the detection of Salmonella typhi in Ganges water using gold nanoparticles as the label. Methodology: gold nanoparticles were synthesized using sodium citrate reduction and characterized using various techniques such as UV-visible spectrometry, fluorescence spectroscopy and TEM. An optimized amount of anti-Salmonella monoclonal antibodies was conjugated with the synthesized gold nanoparticles. An optimum amount of anti-Salmonella polyclonal antibodies and anti-mouse antibodies were coated on nitrocellulose membranes as the test line and control line. The strip detected Salmonella in the sandwich assay format. The developed assay was tested with water samples collected from five different ghats of Ganges, and the results were correlated with conventional culture based methods. Results: statistical validation of the assay results showed that the diagnostic and analytical sensitivity was 100% and 86.7%, respectively. The specificity for the LFIA strip was found to be 100%, and the accuracy of the Salmonella LFIA strip was found to be 93.1%. The positive predictive value and negative predictive value for the LFIA strip was found to be 1 and 0.875, respectively.