Anti-LPS Test Strip for the Detection of Food Contaminated with Salmonella and E. coli

Abstract

Enterobacteria such as E. coli and Salmonella release an endotoxin, or lipopolysaccharide (LPS) that contributes to food poisoning symptoms. We hypothesize that LPS could be detected by a simple strip test, thus detecting the presence of enterobacteria in food. Here we described the development of a novel Anti-LPS detection strip test. Flexible polystyrene test strips with an absorbent poly (vinylidene fluoride) membrane adhered onto one end were exposed to various dilutions of food or bacterial sources. This was followed by the sequential incubation with a primary anti-LPS antibody, biotinylated secondary antibody, and streptavidin-linked enzyme alkaline phosphatase. The test strip was then developed with substrate 5-bromo-4-chloro-3-indolyl phosphate/nitroblue tetrazolium. Thus, the presence of purple precipitate product would indicate the presence of LPS and enterobacteria. The intensity or darkness of the color was quantified densitometrically and compared to LPS standard curve. The test strip assay was shown to readily detect as low as 25 ng/mL of purified LPS. In addition, theanti-LPS test strip assay can sensitively detect and quantify LPS released by live E. coli into culture media. Finally, three food groups (strawberry slices, spinach leaves and ground beef) were inoculated with E. coli for two time points at room temperature and then rinse water from each food preparation was subjected to the anti-LPS test strip assay. For all three food groups, the test strip assay can readily detect and quantify both 8 h and 24 h bacteria contamination over their respective uncontaminated controls. In conclusion, a simple prototype anti-LPS strip test was developed to readily detect enterobacteria contamination of common food.

Gustatory-mediated avoidance of bacterial lipopolysaccharides via TRPA1 activation in Drosophila

“…After starvation, the animals were allowed to feed on a microtiter dish containing wells alternating 100 mM sucrose alone or with 1 mg/ml LPS, mixed with either a red or blue dye (Supplementary Figure 1 , left). This concentration of LPS was chosen in accordance with a previous study reporting concentrations between 250 and 800 µg/ml in water used to rinse fruits and vegetables contaminated with E. coli ( Wang et al, 2011 ). The concentrations in the surface of the food would be therefore much higher than these values, and hence the concentration of 1 mg/ml is likely to be relevant for real scenarios.…”

Lipopolysaccharides: structure, function and bacterial identification

“…Numerous tests based on LPS detection to assess bacterial presence were set up in the past decades. They were used in Elisa and strip tests (Wang et al, 2011).…”

A Comprehensive Assessment and Perception of Genetically Modified Foods

“…The first commercially grown genetically modified whole food crop [29,30] was the tomato also called as Flavr Savr which was made more resistant to rotting by Californian Company Calgene. The tomatoes were released into the market in 1994 without any special labelling.…”