Pathogens In Food Industry Research Articles

NMR-based metabolomic investigation on antimicrobial mechanism of Salmonella on cucumber slices treated with organic acids

The potential of organic acids to inactivate foodborne pathogens in food industry has gained attention, while the sanitizing mechanism of acid stress has not been explained fully at metabolomics level. The aim of this study was to elucidate the antimicrobial mechanism of low-concentration organic acids (1.5% acetic acid, 1% citric acid, and 1.5% lactic acid) on Salmonella enterica strains (ATCC 6962, ATCC 13076, and ATCC 14028) inoculated on cucumber slices. Flow cytometry, nuclear magnetic resonance (NMR) combined with multivariate data analysis revealed that the population of S. enterica reduced 1.7–2.5 log CFU/g after different organic acid treatments. Bacterial membranes (2.37–19.00%) were destroyed and nucleic acid exposed, 40.27–85.33% of membranes was partially damaged, and 44 metabolites were identified from these three strains. The amino acids (Trp, Met, and Val) decreased significantly. Conversely, the intracellular organic acids and hydrocarbon grew obviously. The flux of marked metabolites showed that metabolisms of energy, amino acids, and carbohydrates pathways were disturbed which included TCA cycle, glycolysis, and biosynthesis of amino acids. The antibacterial mechanism on S. enterica provides clue to enhance the application of organic acids in controlling foodborne pathogens on fresh produce.

USE OF BACTERIOPHAGES AS A TARGET SPECIFIC THERAPY AGAINST FOOD-BORNE PATHOGENS IN FOOD INDUSTRY- A REVIEW

Within the context of food safety, the use of modern antimicrobial technologies to inactivate the food-borne pathogens is not infallible, as proven by the ceaseless increase in the food-borne illnesses. The extensive use of antibiotics to minimize the microbial contamination further results in the evolution of antibiotic-resistant bacterial pathogens. Moreover, some of the decontamination methods frequently used in the food industry cannot be directly applied to fresh fruits and vegetables, and RTE meals. Therefore, efforts are being made by researchers in developing a new approach so as to control the bacterial contamination. Consequently, bacteriophages have evolved as the safe, green, effective and natural alternative for treatment and complete destruction of pathogens in food industry. The review provides a general description about bacteriophages and has mainly focused on their potential use as antimicrobials during the postharvest processing of foods. Numerous research papers, review papers, book chapters and other relevant literature was used for writing this review paper.

USE OF BACTERIOPHAGES AS A TARGET SPECIFIC THERAPY AGAINST FOOD-BORNE PATHOGENS IN FOOD INDUSTRY- A REVIEW: Bacteriophage

Within the context of food safety, the use of modern antimicrobial technologies to inactivate the food-borne pathogens is not infallible, as proven by the ceaseless increase in the food-borne illnesses. The extensive use of antibiotics to minimize the microbial contamination further results in the evolution of antibiotic-resistant bacterial pathogens. Moreover, some of the decontamination methods frequently used in the food industry cannot be directly applied to fresh fruits and vegetables, and RTE meals. Therefore, efforts are being made by researchers in developing a new approach so as to control the bacterial contamination. Consequently, bacteriophages have evolved as the safe, green, effective and natural alternative for treatment and complete destruction of pathogens in food industry. The review provides a general description about bacteriophages and has mainly focused on their potential use as antimicrobials during the postharvest processing of foods. Numerous research papers, review papers, book chapters and other relevant literature was used for writing this review paper.

A smart microfluidic platform for rapid multiplexed detection of foodborne pathogens

Rapid and sensitive detection of foodborne pathogens in food industry is of high importance in day-to-day practice to ensure safe food. To address this issue, multiple foodborne pathogens are targeted for rapid identification based in DNA amplification. A 3D PDMS sponge was fabricated using salt crystals as scarifying mold and functionalized with a ligand, apolipoprotein-H (ApoH), to test bacterial capturing for both Gram positive (L. monocytogenes) and negative bacteria (Salmonella spp.), in a microfluidic device. Pure culture of both pathogens in a range of ~10–105 CFU/mL were tested and the application of the developed automated pre-concentration protocol in real samples was verified using spiked surface samples after swab sampling. Bacterial DNA was extracted directly from the sponge and used for Real Time quantitative Polymerase Chain Reaction (qPCR) detection. The sponges did not show any significant resistance to sample flow and could easily be incorporated in a microfluidic device. A capture efficiency above 70% was observed for both targeted (Gram positive and Gram negative) pathogens and a Limit of Detection (LoD) in the range of 103 and 104 CFU/mL was obtained for Salmonella spp. and L. monocytogenes, respectively. Using this approached, we are able to perform multiplexed (Gram positive and Gram negative) capturing and reduce the enrichment time compared to the gold standard plate culture (over 1-day) method. The use of a 3D sponge for direct capturing of multiplexed pathogen on microfluidic device, followed by qPCR detection is an efficient and versatile method to stratify the presence of bacteria. This approach and methodology has potential to be integrated in full automatized device and used as point of need (PoN) system for foodborne pathogen stratification in food packaging/production industries.

Inhibition of bacterial adhesion and biofilm formation of sulfonated chitosan against Pseudomonas aeruginosa

The exploitation of chitosan derivatives as safe and natural polymers against microorganisms has been reconsidered as an alternative to antibiotics and chemical preservatives. Herein, inhibition of bacterial adhesion and biofilm formation by anionic chitosan (sulfonated chitosan, SCS) and cationic chitosan (chitosan hydrochloride, WCS) against P. aeruginosa were investigated. The results showed SCS exhibited good antibacterial activity with 1 mg/mL MIC and 8 mg/mL MBC, while MIC and MBC of WCS were 1 mg/mL and 16 mg/mL, respectively. The metabolic activity and secretion of exopolysaccharide in biofilm of P. aeruginosa were significantly decreased after the treatment with SCS. Scanning electron microscopy and confocal laser scanning microscopy further demonstrated that SCS and WCS could significantly inhibit the biofilm formation in a concentration-dependent mode. Overall, these results suggest that WCS and SCS are useful to inhibit the biofilm formation of P. aeruginosa, and would be potential alternatives for the control of bacterial pathogens in food industry.

Investigation on prevalence of Listeria spp. and Listeria monocytogenes in animal-derived foods by multiplex PCR assay targeting novel genes

Chilled and frozen animal-derived food can be contaminated by Listeria spp., emerging foodborne pathogens in food industry. The objective of this study was to mine novel target genes by comparative genomics approach for multiplex PCR detection and differentiation of Listeria monocytogenes and other Listeria spp. in food. Multiplex PCR assay targeting the genetic markers LMOf2365_2721, AX25_00730, lin1814, int, lwe1673, and Oxidoreductase gene, resulted in the amplification of DNA fragments of 583 bp, 703 bp, 421 bp, 994 bp, 345 bp, and 201 bp from L. monocytogenes, Listeria ivanovii, Listeria innocua, Listeria seeligeri, Listeria welshimeri, and Listeria grayi, respectively. The detection limits of the multiplex assays were as low as 89 fg/μL genomic DNA and 910 CFU/mL of bacterial culture. The prevalence of Listeria spp. was determined using the developed multiplex PCR assay and standard microbiological method in a total of 200 food samples collected from different supermarkets and traditional agri-product markets in Nanjing, China. A total of 28 samples were found to be positive for the presence of Listeria, including 10.9% (6/55) of livestock meat samples, 22% (11/50) of poultry samples, 15% (6/40) of shellfish samples, 13.3% (4/30) of octopus samples and 4% (1/25) of freshwater fish samples. Of these, 13 isolates were classified as L. monocytogenes, 11 were classified as L. innocua, 2 were classified as L. ivanovii and 3 were classified as L. welshimeri. These results demonstrate that the multiplex PCR assay based on novel target genes is able to rapidly detect the Listeria spp. in 12 h with high accuracy and sensitivity, which may be used in the future for detection of Listeria spp. in animal-derived food products.

Genetically modified bacteriophages in applied microbiology.

Bacteriophages represent a simple viral model of basic research with many possibilities for practical application. Due to their ability to infect and kill bacteria, their potential in the treatment of bacterial infection has been examined since their discovery. With advances in molecular biology and gene engineering, the phage application spectrum has been expanded to various medical and biotechnological fields. The construction of bacteriophages with an extended host range or longer viability in the mammalian bloodstream enhances their potential as an alternative to conventional antibiotic treatment. Insertion of active depolymerase genes to their genomes can enforce the biofilm disposal. They can also be engineered to transfer various compounds to the eukaryotic organisms and the bacterial culture, applicable for the vaccine, drug or gene delivery. Phage recombinant lytic enzymes can be applied as enzybiotics in medicine as well as in biotechnology for pathogen detection or programmed cell death in bacterial expression strains. Besides, modified bacteriophages with high specificity can be applied as bioprobes in detection tools to estimate the presence of pathogens in food industry, or utilized in the control of food-borne pathogens as part of the constructed phage-based biosorbents.

Fast and effective: intense pulse light photodynamic inactivation of bacteria

The goal of this study was to investigate the photodynamic toxicity of TMPyP (5, 10, 15, 20-Tetrakis (1-methylpyridinium-4-yl)-porphyrin tetra p-toluenesulfonate) in combination with short pulses (ms) of an intense pulse light source within 10 s against Bacillus atrophaeus, Staphylococcus aureus, Methicillin-resistant S. aureus and Escherichia coli, major pathogens in food industry and in health care, respectively. Bacteria were incubated with a photoactive dye (TMPyP) that is subsequently irradiated with visible light flashes of 100 ms to induce oxidative damage immediately by generation of reactive oxygen species like singlet oxygen. A photodynamic killing efficacy of up to 6 log(10) (>99.9999%) was achieved within a total treatment time of 10 s using a concentration range of 1-100 μmol TMPyP and multiple light flashes of 100 ms (from 20 J cm(-2) up to 80 J cm(-2)). Both incubation of bacteria with TMPyP alone or application of light flashes only did not have any negative effect on bacteria survival. Here we could demonstrate for the first time that the combination of TMPyP as the respective photosensitizer and a light flash of 100 ms of an intense pulsed light source is enough to generate sufficient amounts of reactive oxygen species to kill these pathogens within a few seconds. Increasing antibiotic resistance requires fast and efficient new approaches to kill bacteria, therefore the photodynamic process seems to be a promising tool for disinfection of horizontal surfaces in industry and clinical purposes where savings in time is a critical point to achieve efficient inactivation of microorganisms.

Hierarchical Bayesian Modelling for Saccharomyces cerevisiae population dynamics

Hierarchical Bayesian Modelling is powerful however under-used to model and evaluate the risks associated with the development of pathogens in food industry, to predict exotic invasions, species extinctions and development of emerging diseases, or to assess chemical risks. Modelling population dynamics of Saccharomyces cerevisiae considering its biodiversity and other sources of variability is crucial for selecting strains meeting industrial needs. Using this approach, we studied the population dynamics of S. cerevisiae, the domesticated yeast, widely encountered in food industry, notably in brewery, vinery, bakery and distillery. We relied on a logistic equation to estimate the key variables of population growth, but we took also into account factors able to affect them, namely environmental effects, genetic diversity and measurement errors. Our probabilistic approach allowed us: (i) to model the dynamical behaviour of strains in a given condition under some uncertainty, (ii) to measure environmental effects and (iii) to evaluate genetic variability of the growth key variables.

Adhesion of Salmonella Enteritidis to stainless steel surfaces

Adhesion of microorganisms to food processing surfaces and the problems it causes are a matter of strong concern to the food industry. Contaminated food processing surfaces may act as potential sources of transmission of pathogens in food industry, catering and in the domestic environments. Several studies have shown that adhesion of bacteria to surfaces partly depends upon the nature of the inert surfaces and partly upon the bacterial surface properties. The aim of this study was to compare the adhesion of four different strains of Salmonella Enteritidis to stainless steel 304 (SS 304). The effect of surface hydrophobicity and surface elemental composition on the adhesion process was also analysed. Hydrophobicity was evaluated through contact angle measurements using the sessile drop method. All the strains studied showed positive values of the degree of hydrophobicity (deltaGlwl) and so can be considered hydrophilic while stainless steel revealed a hydrophobic character. Bacterial cell surface composition was measured using X-ray photoelectron spectroscopy (XPS). The XPS results corroborated the similarity of the values of the degree of hydrophobicity obtained by contact angles. The different Salmonella strains showed similar elemental composition and cell surface physico-chemical properties. Nevertheless, S. Enteritidis MUSC presented higher adhesion ability to SS 304 (p<0.05). It can be concluded that the physico-chemical properties of the strain does not explain the ability of adhesion to stainless steel. Other factors like the production of polysaccharides must be considered.