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Abstract Shigella flexneri is one of the major food-borne pathogens in China. Herein, we reported the development of a colorimetric aptasensor based on aptamer and gold nanoparticles (AuNPs) for detection of Sh. flexneri. Aptamer with high binding affinity to Sh. flexneri was firstly immobilized on the surface of AuNPs, and detection was accomplished through aggregation of AuNPs induced by target bacteria, which was associated with color changes of the reaction after addition of NaCl. Under the optimum conditions, a linear calibration relationship was obtained between the ratio of A700/A520 and concentrations of Sh. flexneri over the range from 102 to 106 CFU/mL. The detection limit was 80 CFU/mL, and detection time was 20 min or less. Specificity test and real samples analysis indicated that the colorimetric aptasensor was efficient in terms of reliability and detection time as compared with conventional culture examination. Without preconcentration and DNA extraction steps, the developed colorimetric aptasensor is simple, convenient, and suitable for on-site detection of Sh. flexneri. We expect that the developed novel method will facilitate further advances in rapid screening of other food-borne pathogens using suitable aptamers. Highlights • A colorimetric aptasensor was used to visual detection of Sh. flexneri. • A linear calibration curve was shown from 102 to 106 CFU/mL with a LOD of 80 CFU/mL. • The detection was highly specific, and detection time was 20 min or less. • The developed assay is suitable for rapid and on-site detection of Sh. flexneri. [ABSTRACT FROM AUTHOR]

Essential oils (EOs) have deserved much attention in the past decades for their antimicrobial activity, since many of them have demonstrated efficacy against food-borne pathogenic and spoilage microorganisms. Moreover, they have potential application in animal nutrition as multifunctional feed supplements, avoiding or diminishing the use of antibiotics in livestock. However, low solubility and bioavailability as well as volatility and marked aromatic note are important limitations in food and feed applications. In this study we present the synthesis, characterization and evaluation of the antibacterial activity of new thymol, carvacrol and menthol derivatives. The new compounds have been designed to overcome the limitations of the precursors, such as poor water solubility and volatility, still maintaining a good antimicrobial profile. We evaluated the activity of the synthetized compounds against pathogens causing important foodborne diseases, i . e . Clostridium perfringens , Salmonella typhimurium , Salmonella enteritidis and Escherichia coli . The low MICs and MBCs values for some of the studied compounds, combined with water solubility and negligible cytotoxicity towards HT-29 human cells, confirmed the potential use for EOs derivatives in the food industry. [ABSTRACT FROM AUTHOR]

Table olives are one of the most important fermented vegetables in the Mediterranean countries. Although this fermented vegetable has a long record of microbial safety, various studies have shown the presence of Listeria monocytogenes during table olive processing. This study focused on evaluating the behaviour of a cocktail of L. monocytogenes strains during fermentation of Spanish-style green Manzanilla olives. For this purpose, a challenge test consisting of artificial inoculation of olive fermentation with high levels of the food-borne pathogen (7.0 log 10 CFU/ml) was performed. The fermentation was carried out at the laboratory scale in sealed glass bottles (n = 168) under controlled conditions to avoid the initiation of lactic acid fermentation intentionally. This point was confirmed by the evolution of pH, which ranged from an initial 9.0 to final 6.0 units (decrease kinetic constant of −0.0016 h−1), as well as by the behaviour of lactic acid and mesophilic bacteria during the study (55 days). The fate of L. monocytogenes during fermentation was described using mathematical models, including the two-term Gompertz equation. During this time, the food-borne pathogen showed an initial growth phase which lasted until 250 h, reaching a maximum population level close to 9.0 log 10 CFU/ml, even in the presence of high salt concentrations (>6.0% NaCl). Then, a rapid decline phase was observed but continuously detecting a residual tail of around 2 log 10 CFU/ml. Data obtained in this work shows the importance of the control of olive fermentation, especially during the first weeks when pH is alkaline-neutral and environmental conditions could favour L. monocytogenes growth. • A challenge test with Listeria monocytogenes in olive fermentations was performed. • Inoculated Listeria monocytogenes during table olive storage decreased. • L. monocytogenes two-term Gompertz model was developed. • To reduce the risk of Listeria it is necessary to lower the pH during fermentation. [ABSTRACT FROM AUTHOR]

A colloidal gold immunochromatographic strip (ICS) was proposed with double monoclonal antibodies (McAbs) for rapid detections of multiple foodborne pathogens, and we successfully developed a model strip for simultaneous detection of Shigella boydii ( S. boydii ) and Escherichia coli O157:H7 ( E. coli O157:H7) in this study. The sensitivity of the strip test was determined to be 10 6 CFU/mL for both S. boydii and E. coli O157:H7. There was no cross-reaction with other related bacteria. Parallel analysis of pathogen detection from bread, milk and jelly showed consistent results between the strip test and enzyme-linked immunosorbent assay (ELISA). The detection limit was substantially improved to 4 CFU/mL of the original bacterial content after pre-incubation of the bread, milk and jelly samples in broth for 10, 10 and 8 h respectively. This ICS was able to finish test within 5–10 min and has advantages in high throughput and easy operation without requiring sophisticated equipment and specialized skills. Overall, to our knowledge, this is the first report of semi-quantitative ICS for simultaneously detecting two pathogens. This protocol might provide insight into the development of ICS technology for simultaneously examining multiple food-borne pathogens from foods. [ABSTRACT FROM AUTHOR]

The antimicrobial effect of high hydrostatic pressure (HHP) processing combined with reuterin, lactoperoxydase system (LPS) and lactoferrin (LF) on the survival of Listeria monocytogenes , Salmonella enterica subsp. enterica serovar Enteritidis and Escherichia coli O157:H7 in sliced cooked ham stored under strict refrigeration temperature (4 °C) and mild temperature abuse conditions (10 °C) was investigated. One day after treatment, L. monocytogenes counts in HHP at 450 MPa for 5 min were 0.8 log units lower, but a recovery was observed with counts not significantly different to those observed in control after 35 d. S. Enteritidis and E. coli O157:H7 levels were reduced around 5 log cfu/g by the pressure treatment (450 MPa/5 min) and the numbers of these pathogens did not increase significantly during the 35 d of storage at 4 °C. The individual application of reuterin and LPS influenced the survival of the three pathogens studied, extending the lag phase of L. monocytogenes and diminishing S. Enteritidis and E. coli levels throughout storage, whereas no effect was recorded when LF was added. When reuterin or LPS were applied in combination with HHP there was a synergistic antimicrobial effect against L. monocytogenes , avoiding at 4 °C the recovery observed with individual treatments. These combined treatments also kept the levels of S. Enteritidis and E. coli O157:H7 below the detection limit (<1 log unit) in cooked ham stored at 4 and 10 °C during 35 d. The results obtained in the present work suggest that HHP at 450 MPa for 5 min in combination with LPS or reuterin would be useful as a hurdle technology approach against L. monocytogenes , S. Enteritidis and E. coli O157:H7 in cooked ham. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper, multiplex polymerase chain reaction (PCR) was coupled to a suspension array to construct an assay for simultaneous identification of six kinds of pathogens. The suspension array allows the simultaneous detection of different target sequences in a multiplex and high-throughput format. The assay uses a liquid suspension hybridization format with specific oligonucleotide probes covalently bound to the surface of fluorescent color-coded microspheres. Biotinylated target amplicons, hybridized to their complementary probe sequences, are quantified by adding the conjugate, streptavidin R-phycoerythrin. Six probes derived from the sequence analysis of a specific gene were developed and validated. There was little cross-reaction among the various probes. In the multi-channel method, the detection sensitivity was 1.6 × 10−6 mM. Results of nucleic acid detection assays show detection sensitivity for 20–4 × 103 CFU/ml, which is one to five orders of magnitude higher than those of PCR-agarose method in different bacteria. Aside from single channel capability, the assay allows the simultaneous detection of target genes in a single reaction, with detection limits of 1–10 CFU/ml. The accuracy, speed, flexibility, and sensitivity of the proposed assay are beneficial for the diagnosis of pathogenic diseases. [Copyright &y& Elsevier]

Abstract: The present investigation reports on the chemical composition of Cudrania tricuspidata fruit essential oil (CTEO) and examines its possible antimicrobial mode of action against food-borne pathogenic bacteria. The CTEO was obtained by hydrodistillation of C. tricuspidata fruits using a microwave-assisted extraction technique. Gas chromatography-mass spectrometry analysis of the CTEO resulted in the determination of 29 different compounds, representing 94.46% of the total oil. The CTEO (1000 μg/disc) showed potential antibacterial effect as diameters of inhibition zones (15.0 ± 0.1–21.0 ± 1.0 mm) against the tested food-borne pathogenic bacteria including Bacillus cereus ATCC 13061, Staphylococcus aureus ATCC 12600, Listeria monocytogenes ATCC 7644, Salmonella typhimurium ATCC 43174 and Escherichia coli O157:H7 ATCC 43889. The minimum inhibitory (MIC) and minimum bactericidal (MBC) concentration values of CTEO against the tested bacteria were found in the range of 250–1000 μg/mL, respectively. Also the CTEO had potential inhibitory effect on the cell viability of the tested pathogens at MIC concentration. The SEM analysis showed the inhibitory effect of CTEO as confirmed by considerable morphological alterations on the cell wall B. cereus ATCC 13061 and E. coli O157:H7 ATCC 43889. In addition, the CTEO revealed its mode of action on membrane integrity as confirmed by release of extracellular ATP, loss of 260-nm absorbing materials and leakage of potassium ions against food-borne pathogenic bacteria. These findings suggest that CTEO showed a broad-spectrum of antibacterial efficacy and compromise its mode of action on membrane integrity. [Copyright &y& Elsevier]

Abstract: A novel application of GeXP analyzer was developed for simultaneous detection of six pathogens associated with food poisoning outbreaks, including Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Shigella spp., and Campylobacter jejuni. Chimeric primers containing both microbe- and pMD19-specific sequences were fused to universal sequences resulted in PCR products with intended sizes. The PCR products were separated by capillary electrophoresis and identified by using fluorescence spectrophotometry. Plasmid pMD19-T was added to each reaction as positive control to ascertain the PCR steps and data analysis step of the assay. The results indicate that the GeXP method is both specific and sensitive for the detection of all six food-borne pathogens in a single reaction-without any enrichment step. In conclusion, the GeXP-PCR assay is a rapid, sensitive and high-throughput method for parallel analysis of food-borne pathogens. [Copyright &y& Elsevier]

Abstract: This study was aimed to evaluate the anti-bacterial potential of the essential oil and extracts of Trachyspermum ammi fruits against food borne and spoilage bacteria. The chemical compositions of the oil were analyzed by GC–MS. Thirty compounds representing 91.39% of the total oil were identified. The extracellular ATP concentration, release of cell constituents and potassium ions from the bacterial cell were measured after treatment with essential oil of T. ammi at MIC concentration. The oil, and extracts of hexane, chloroform, ethyl acetate and methanol of T. ammi fruits displayed remarkable anti-bacterial effects against Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa KCTC 2004, Salmonella typhimurium KCTC 2515, Enterobactor aerogens KCTC 2190 and Staphylococcus aureus ATCC 6538. The scanning electron microscopic studies also demonstrated inhibitory effect of the oil on the morphology of B. subtilis ATCC 6633 at the MIC concentration, along with the potential effect on cell viabilities of the tested bacteria. [Copyright &y& Elsevier]

Abstract: Antimicrobial activity of reuterin in combination with different bacteriocins from lactic acid bacteria against food-borne pathogens in milk was investigated. A strong synergistic effect of reuterin in combination with nisin, lacticin 481 or enterocin AS-48 on Listeria monocytogenes was observed. Only nisin increased the antimicrobial activity of reuterin against Staphylococcus aureus. Bactericidal activity of reuterin towards Escherichia coli O157:H7, Salmonella enterica, Yersinia enterocolitica, Aeromonas hydrophila and Campylobacter jejuni was not enhanced significantly by the addition of any of the bacteriocins investigated. The synergism of reuterin and nisin against L. monocytogenes and S. aureus was also found at refrigeration temperatures, where the pathogens were completely inactivated. Refrigerated milk treated with both natural antimicrobials would mean a feasible system to control pathogenic contaminants. [ABSTRACT FROM AUTHOR]

Abstract: Herbs and spices containing essential oils (EOs) in the range of 0.05–0.1% have demonstrated activity against pathogens, such as Salmonella typhimurium, Escherichia coli O157:H7, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus, in food systems. Application of herbs, spices and EOs with antimicrobial effects comparable to synthetic additives is still remote for three major reasons: limited data about their effects in food, strong odor, and high cost. Combinations of techniques have been successfully applied in several in-food and in vitro experiments. This paper aims to review recent in-food applications of EOs and plant-origin natural antimicrobials and recent techniques for screening such compounds. [Copyright &y& Elsevier]

Abstract: Fermented sausage technology involves a sequence of hurdles that appear along the ripening process. A wide variety of fermented sausages are manufactured worldwide based on the concept of reduction of pH and/or water activity. In low acid fermented sausages the absence of high acidification can be balanced by the application of additional hurdles such as bacteriocins and/or high hydrostatic pressure (HHP). The addition of enterocins A and B to raw-sausages spiked with 3logCFU/g of Salmonella, Listeria monocytogenes and Staphylococcus aureus showed an immediate reduction in the counts of L. monocytogenes due to the enterocins, while Salmonella was more affected by the endogenous hurdles associated with the ripening process. The application of an HHP treatment of 400MPa at the end of ripening produced an immediate reduction in the counts of Salmonella but not in L. monocytogenes or S. aureus. During storage of the low acid sausages (fuets) at room temperature and at 7°C, counts of Salmonella and L. monocytogenes progressively decreased in all batches although the decrease was faster in the pressurized ones stored at room temperature. At the end of storage, Salmonella was <1 logCFU/g in all the batches but only the combination of enterocins and HHP could reduce the counts of L. monocytogenes to this level. Neither the ripening process, the enterocins nor the pressurization could control the levels of S. aureus. [Copyright &y& Elsevier]

Abstract: Numerous virulence factors including adhesins, host cell surface-modifying factors, invasins, toxins, and secretion systems are involved in Escherichia coli pathogenicity mechanisms. Strains of the same pathotype are genetically similar and carry the same virulence determinants which are ideal targets for the determination of the pathogenic potential of any given E. coli isolate. We examined 95 strains of E. coli isolated from two kinds of traditional Slovak cheeses made from raw sheep milk in course of one year. We tested those strains with the goal to determine some of 11 selected genes of virulence factors which at least partially represent all frequent pathotypes of E. coli. Markers of VTEC (VT1,VT2,VT2e), ETEC (ST I,ST II,LT I), EPEC (EaeA), EIEC (Einv), EAEC (Eagg), and UPEC (CNF1,CNF2) were examined using PCR assays. The result of our testing was the determination of nine potentially pathogenic strains from 95 isolates (9.72%). We did not prove VT1 and VT2 factors as well as Einv and Eagg in any strains. We detected ST I in two strains, ST II and LT I in one strain, and VT2e in one strain. In this study most frequent virulence markers were CNF 1 (three strains) and EaeA (three strains). [Copyright &y& Elsevier]

A local market survey of fresh, raw coriander leaves, which is a component of many ready-to-eat, Indian dishes showed large variation in their bacterial load (7.0×106–1.36×108 cfu/gm) and mold and fungi (3.0×103–1.0×104 cfu/gm) and presence of potentially pathogenic bacteria such as faecal coliforms, Listeria and Yersinia. Conventional chlorination treatment affected the structural integrity of leaves leading to enhancement of rotting. Exposure to a low dose of 1 kGy was efficient for bacterial decontamination and elimination of potential pathogens without affecting the keeping quality of coriander leaves upto two weeks storage at 8–10 °C, measured visually in terms of degree of yellowing and rotting. Irradiation at higher doses led to the increased rotting during storage. The total chlorophyll contents as well its components, chlorophyll a and b did not change significantly on irradiation and subsequent storage. Similarly, the total carotenoid levels remained unaffected by exposure to 1 kGy dose, however, a dose dependent enhancement in their extractability was observed in irradiated leaves. No qualitative differences were observed in the GLC profile of volatile oils of control and irradiated (1 kGy) samples. There were no significant quantitative changes in the constituents of the major aroma compounds obtained from these two samples. Effects of irradiation on storage of the seasoning were also assessed. [Copyright &y& Elsevier]

The hide of cattle is known to be a source for the microbial contamination of beef, with microorganisms transferred onto the carcass from the hide, during the slaughter and dressing processes. To assess the potential risk of carcass contamination from food-borne bacterial pathogens on cattle hides, a study was carried out involving 90 beef cattle in the South-West of England to determine the prevalence of these microorganisms. A one-pass swab technique was carried out to sample a measured area on the rump, flank and brisket of each animal. These swabs were processed in the laboratory to determine the prevalence of E. coli O157, Salmonella spp., and Campylobacter spp. on these hide areas. The most contaminated area was the brisket with one in five animals testing positive for E. coli O157 (22.2% prevalence on average) and approximately one in 10 animals testing positive for Salmonella spp. (10.0% prevalence on average). The least contaminated area on the cattle hides was the rump area (3.3% prevalence for E. coli O157, 2.2% prevalence for Salmonella spp.). Campylobacter spp. was not isolated from any samples taken from the 90 cattle studied. The results of this study indicate that the brisket area on the hide of cattle most frequently carries food-borne pathogens and is therefore most likely to lead to cross-contamination of beef during the de-hiding process. [Copyright &y& Elsevier]