Rapid and simultaneous detection of Salmonella spp., Escherichia coli O157, and Listeria monocytogenes by magnetic capture hybridization and multiplex real-time PCR

The application of rapid, specific, and sensitive methods for pathogen detection and quantification is very advantageous in diagnosis of human pathogens in several applications, including food analysis. The aim of this study was the evaluation of a method for the multiplexed detection and quantification of three significant foodborne pathogenic species (Escherichia coli O157, Salmonella spp., and Listeria monocytogenes). The assay combines specific DNA extraction by multiplex magnetic capture hybridization (mMCH) with multiplex real-time PCR. The amplification assay showed linearity in the range 106 –10 genomic units (GU)/PCR for each co-amplified species. The sensitivity corresponded to 1 GU/PCR for E. coli O157 and L. monocytogenes, and 10 GU/PCR for Salmonella spp. The immobilization process and the hybrid capture of the MCH showed good efficiency and reproducibility for all targets, allowing the combination in equal amounts of the different nanoparticle types in mMCH. MCH and mMCH efficiencies were similar. The detection limit of the method was 10 CFU in samples with individual pathogens and 102 CFU in samples with combination of the three pathogens in unequal amounts (amount’s differences of 2 or 3 log). In conclusion, this multiplex molecular platform can be applied to determine the presence of target species in food samples after culture enrichment. In this way, this method could be a time-saving and sensitive tool to be used in routine diagnosis

Influence of low molecular weight surfactants on the stability of model infant formula emulsions based on hydrolyzed rice protein

The emulsifying properties of rice protein ingredients, and their behaviour in the presence of other non-protein emulsifiers, are essential to support food applications. The objective of this study was to investigate the influence of different low molecular weight surfactants (LMWS) on the stability of model infant formula emulsions (10 g protein L−1, 35 g soybean oil L−1, 50 g carbohydrate L−1) based on a rice protein hydrolyzate (RPH). Inclusion of CITREM and DATEM, at concentrations greater than 1 g L−1, gave emulsions with mean fat globule diameters (D[4,3]) less than 1 μm with good creaming stability, while lecithin was less effective across the concentration range tested (i.e., 1-3 g L−1). Coalescence of the control emulsion was observed upon both storage (10 d at 4 °C) and heat treatment (95 °C x 5 min). Increasing CITREM concentration increased storage and heat stability of the emulsions, while addition of CITREM at 2 g L−1 facilitated the formation of a very stable product. This study provides a first insight into the potential of hydrolyzed rice protein to be used as a value-added ingredient in the production of nutritional beverages such as infant formula emulsions, and the influence of LMWS on the stability of such products

Detection of Shiga toxin-producing Escherichia coli (STEC) in ground beef and bean sprouts: Evaluation of culture enrichment conditions

The main purpose of this work was to evaluate culture enrichment conditions, with particular regard to those reported in ISO/TS 13136:2012, for STEC detection in food. The culture media evaluated included mTSB with novobiocin 0-16 mg/l (mTSB + N0-16) or acriflavin 12 mg/l (mTSB + A(12)); BPW; mBPWp with acriflavin 10 mg/l, cefsulodin 10 mg/l, vancomycin 8 mg/l (mBPWp + ACV); and mBPWp with cefsulodin 10 mg/l, vancomycin 8 mg/l (mBPWp + CV). They were used for the growth of STEC 0157, 026, 0103, 0111, 0145 and 0104 in pure cultures or in artificially contaminated food matrices (ground beef, mung bean sprouts). STEC detection was accomplished using commercially available multiplex real-time PCR assays targeting stxl-stx2 and eae, and serogroup-associated genes. More rapid multiplication of STEC in pure cultures occurred in mBPWp + CV, while an inhibitory effect of novobiocin and acriflavin was observed for some STEC serogroups in media with these selective agents. mBPWp + CV allowed the detection of all serogroups in bean sprouts when inoculated at levels as low as 1 CFU/25 g. A reduced novobiocin concentration of 2 mg/l in mTSB was required for STEC detection in ground beef samples. A temperature of 42 degrees C for the entire duration of the enrichment or 44 degrees C after an initial phase of 6 h at 37 degrees C was important to limit the multiplication of non-target bacteria. Results of this study suggest that media and protocols should be adapted to the food being analyzed, since protocols provided in official reference methods may produce insufficient sensitivity

An IoT Virtual Sensor for Indoor Health Risk Assessment

Indoor environments have a significant impact on human health and well-being. With the increasing urbanization and the amount of time individuals spend indoors, there is a growing need for accurate and real-time monitoring of air quality and health risks. Moreover, the mere presence of people inside closed environments, in addition to saturating the environment with gases typically produced by human respiration, entails contamination of a microbiological nature due, for example, from exhaled aerosols which can contain several pathogens. In this study, we propose an Internet of Things virtual sensor for indoor health risk assessment that integrates several physical sensors measuring various parameters related to indoor air quality, including temperature, humidity, carbon dioxide levels, volatile organic compounds, and particulate matter with the purpose to indirectly estimate the bacterial load present in the air. Preliminary results, obtained in a real testbed, demonstrate, from the qualitative point of view, the appropriateness of the proposed device