Development of a biosensor for the rapid detection of Salmonella Typhimurium in milk

Abstract

Foodborne illnesses are still serious problems in the United States. Methods for rapid detection of foodborne pathogens are needed to protect public health. The recent advances in biosensor technology enabled the rapid detection of pathogens. The purpose of this research was to develop a biosensor for the rapid detection of Salmonella in milk. In the first study, a 55 kD purified outer membrane protein (OMP) of S. enterica Typhimurium was used to produce monoclonal and polyclonal antibodies. The S. enterica Typhimurium specific monoclonal antibody (mAb) 1B4 was immobilized on a sensor platform as a bacterial capture agent, and the captured S. enterica Typhimurium was visualized by a light microscope. The developed biosensor has a detection limit of 102 cfu/ml. In the second study, one step enrichment in conjunction with a centrifugation technique was investigated. In order to increase the relatively low number of Salmonella in milk, 7 non-selective and 5 selective enrichment media were compared. Among these media, brain heart infusion broth (BHI) and brilliant green broth (BG) were the most efficient. These media were able to increase Salmonella concentration from 0.01 cfu/ml to above 102 cfu/ml in 6 h. The centrifugation technique used in this study was able to concentrate bacteria up to 50 times. In conjunction with centrifugation, enrichment in BG or BHI for 4 h could increase Salmonella concentration from 0.01 cfu/ml to a detectable level. The milk content, excessive amounts of other bacteria, and enrichment broth content did not affect the detection sensitivity and specificity of the developed biosensor. The developed biosensor was found to be a rapid and sensitive method for the detection of S. enterica Typhimurium in milk. Total time needed for the detection of 0.1 cfu/ml S. enterica Typhimurium in milk was 5 h.