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Comparison of six commercial systems for the detection of non-O157 STEC in meat and vegetables.
Costa, M, Sucari, A, Epszteyn, S, Oteiza, J, Gentiluomo, J, Melamed, C, Figueroa, Y, Mingorance, S, Grisaro, A, Spioussas, S, et al
Food microbiology. 2019;:103273
Abstract
Shiga toxin-producing Escherichia coli (STEC) are important pathogens transmitted by food that may cause severe illness in human beings. Thus, systems for STEC detection in food should have increasingly higher sensitivity and specificity. Here we compared six commercial systems for non-O157 STEC detection in meat and vegetables and determined their sensitivity, specificity and repeatability. A total of 46 samples (meat n = 23; chard n = 23) were experimentally contaminated with strains O26:H11, O45:H-, O103:H2, O111:NM, O121:H19 and O145:NM isolated in Argentina. Strain detection was confirmed by isolation according to ISO 13136:2012. Detection of the stx and eae genes in meat samples was highly satisfactory with all commercial kits, but only five had 100% sensitivity and specificity in chard. Of four kits evaluated for serogroup detection, three had 100% sensitivity and specificity, and one had 93.7% sensitivity and 100% specificity. All kits were adequate to analyze meat but not vegetable samples, and were not therefore validated for the latter matrix. The challenge for microbiology laboratories is to identify the advantages and disadvantages of the available kits for STEC detection in food based on a clear knowledge of the particular needs of each laboratory.
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2.
ELIME assay vs Real-Time PCR and conventional culture method for an effective detection of Salmonella in fresh leafy green vegetables.
Fabiani, L, Pucci, E, Delibato, E, Volpe, G, Piermarini, S, De Medici, D, Capuano, F, Palleschi, G
Talanta. 2017;:321-327
Abstract
The detection of Salmonella according to EC regulation is still primarily based on traditional microbiological culture methods that may take several days to be completed. The purpose of this work is to demonstrate the applicability of an Enzyme-Linked-Immuno-Magnetic-Electrochemical (ELIME) assay, recently developed by our research group for the detection of salmonella in irrigation water, in fresh (raw and ready-to-eat) leafy green vegetables by comparison with Real-Time PCR (RTi-PCR) and ISO culture methods. Since vegetables represent a more complex matrix than irrigation water, preliminary experiments were carried out on two leafy green vegetables that resulted negative for salmonella by the ISO method. 25g of these samples were experimentally inoculated with 1-10 CFU of S. Napoli or S. Thompson and pre-enriched for 20h in two different broths. At this time aliquots were taken, concentrated at different levels by centrifugation, and analyzed by ELIME and RTi-PCR. Once selected the best culture medium for salmonella growth, and the optimal concentration factor suitable to reduce the sample matrix effect, enhancing the out-put signal, several raw and ready-to-eat leafy green vegetables were artificially inoculated and pre-enriched. Aliquots were then taken at different incubation times and analyzed with both techniques. Results obtained showed that 20 and 8h of pre-enrichment were required to allow the target salmonella (1-10 CFU/25g) to multiply until reaching a detectable concentration by ELIME and RTi-PCR assays, respectively. A confirmation with the ISO culture method was carried out. Based on the available literature, this is the first report of the application of an ELISA based method for the detection of Salmonella in vegetables.
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3.
Clostridial spore germination versus bacilli: genome mining and current insights.
Xiao, Y, Francke, C, Abee, T, Wells-Bennik, MH
Food microbiology. 2011;(2):266-74
Abstract
Bacilli and clostridia share the characteristic of forming metabolically inactive endospores. Spores are highly resistant to adverse environmental conditions including heat, and their ubiquitous presence in nature makes them inevitable contaminants of foods and food ingredients. Spores can germinate under favourable conditions, and the following outgrowth can lead to food spoilage and foodborne illness. Germination of spores has been best studied in Bacillus species, but the process of spore germination is less well understood in anaerobic clostridia. This paper describes a genome mining approach focusing on the genes related to spore germination of clostridia. To this end, 12 representative sequenced Bacillus genomes and 24 Clostridium genomes were analyzed for the distribution of known and putative germination-related genes and their homologues. Overall, the number of ger operons encoding germinant receptors is lower in clostridia than in bacilli, and some Clostridium species are predicted to produce cortex-lytic enzymes that are different from the ones encountered in bacilli. The in silico germination model constructed for clostridia was linked to recently obtained experimental data for selected germination determinants, mainly in Clostridium perfringens. Similarities and differences between germination mechanisms of bacilli and clostridia will be discussed.
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4.
Identification of 9(E),11(E)-18:2 fatty acid methyl ester at trace level in thermal stressed olive oils by GC coupled to acetonitrile CI-MS and CI-MS/MS, a possible marker for adulteration by addition of deodorized olive oil.
Saba, A, Mazzini, F, Raffaelli, A, Mattei, A, Salvadori, P
Journal of agricultural and food chemistry. 2005;(12):4867-72
Abstract
The olive oil market is suffering from sophisticated illegal treatments. One common adulteration process consists of the addition to virgin olive oil of lower quality oils, such as "lampante" oil, an inexpensive oil and with some organoleptic defects, which is then submitted to thermal deodorization under vacuum processes for removal of the undesired flavor components. Such a blending may not have a huge influence on the chemical composition and may not significantly affect the parameters usually checked as quality indicators, although the organoleptic properties may change. As a consequence, a major effort is being devoted to find reliable markers able to unmask such adulterations. We report here the complete characterization of a compound, detected at trace levels exclusively in thermal stressed oils, which could be a candidate marker for adulteration. The investigation, carried out by GC-MS and GC-MS/MS, provided its complete structure, including the stereochemistry, shown to be a 9(E),11(E)-18:2 fatty acid methyl ester. Experimental data also confirmed the influence of both temperature and heating time on formation and concentration of this compound.
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5.
A multi-residue screening method for the determination of 73 pesticides and metabolites in fruit and vegetables using high-performance liquid chromatography/tandem mass spectrometry.
Hetherton, CL, Sykes, MD, Fussell, RJ, Goodall, DM
Rapid communications in mass spectrometry : RCM. 2004;(20):2443-50
Abstract
A multi-residue screening method was developed for the simultaneous analysis of 73 pesticides and their metabolites using high-performance liquid chromatography coupled with electrospray tandem mass spectrometry. These pesticides were determined under a single set of experimental conditions involving a simple acetonitrile extraction without the requirement for a clean-up step. Validation was achieved at 0.01 and 0.1 mg kg(-1) levels in apple, lettuce and orange. Recoveries were in the range 77-124% for the majority of pesticides.
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6.
The contribution of epidemiology.
van den Brandt, P, Voorrips, L, Hertz-Picciotto, I, Shuker, D, Boeing, H, Speijers, G, Guittard, C, Kleiner, J, Knowles, M, Wolk, A, et al
Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association. 2002;(2-3):387-424
Abstract
Epidemiologic studies directly contribute data on risk (or benefit) in humans as the investigated species, and in the full food intake range normally encountered by humans. This paper starts with introducing the epidemiologic approach, followed by a discussion of perceived differences between toxicological and epidemiologic risk assessment. Areas of contribution of epidemiology to the risk assessment process are identified, and ideas for tailoring epidemiologic studies to the risk assessment procedures are suggested, dealing with data collection, analyses and reporting of both existing and new epidemiologic studies. The dietary habits and subsequent disease occurrence of over three million people are currently under observation worldwide in cohort studies, offering great potential for use in risk assessment. The use of biomarkers and data on genetic susceptibility are discussed. The paper describes a scheme to classify epidemiologic studies for use in risk assessment, and deals with combining evidence from multiple studies. Using a matrix approach, the potential contribution to each of the steps in the risk assessment process is evaluated for categories of food substances. The contribution to risk assessment of specific food substances depends on the quality of the exposure information. Strengths and weaknesses are summarized. It is concluded that epidemiology can contribute significantly to hazard identification, hazard characterisation and exposure assessment.