New approach for discrimination of Vibrio vulnificus by real-time PCR before and after gamma-irradiation

Molecular DNA-based detection of ionising radiation in meat

BACKGROUND

Ionising radiation induces molecular alterations, such as formation of ions, free radicals, and new stable molecules, and cleavage of the chemical bonds of the molecules present in food. Irradiation-treated meat should be labelled to control the process and to ensure free consumer choice. Therefore, sensitive analytical methods are required to detect the irradiation dose.

RESULTS

Meat samples were exposed to radiation doses of 0, 0.272, 0.497, 1.063, 3.64, 8.82 and 17.42 kGy in an industrial ⁶⁰ Co gamma cell. Primers were designed to amplify 998, 498 and 250-base pair (bp) regions of the 18S rRNA gene of nuclear DNA from the irradiated samples. A new DNA-based method was developed to quantify the radiation exposed to the unstored meat and the meat stored at -20 °C for 3 and 6 months. The method was able to detect meat samples stored and unstored with dose limits of 1.063 and 3.64 kGy, respectively.

CONCLUSION

The level of irradiation can be detected using primer pairs that target particularly different-sized sequences for DNA amplification by PCR. This method can be widely used for the analysis of not only meat samples, but also all biological materials containing DNA. © 2016 Society of Chemical Industry.

A new measurement approach of ionizing radiation in irradiated trout (Oncorhynchus mykiss) by Randomly Polymorphic DNA-Polymerase Chain Reaction

Trout (Oncorhynchus mykiss) were irradiated at doses of 0.250, 0.500, 1, 3, 5, 7 and 9 kGy in gamma cell. DNAs were extracted from the irradiated samples before and after storage. 1ERP primers were designed, and RAPD-PCR (Randomly Polymorphic DNA-Polymerase Chain Reaction) was applied to make randomly amplifications on the DNA of the irradiated samples. Agarose gel profiles of irradiated fish were obtained to determine change of band profiles. In addition, DNA fragmentation occurring in each dose was determined by comet assay for the verification of methodology developed in this study. The molecular methodology was developed to estimate ionizing radiation (IR) level in irradiated fish. This methodology allows the analysis of the trout irradiated up to the dose limit of around 0.5 kGy and stored for a period of three months.

Determination of irradiation dose and distinguishing between irradiated and non irradiated fish meat by real-time PCR

In this study, the effects of gamma irradiation on the DNA of fish (Oncorhynchus mykiss) by real-time PCR were studied. Fish (O. mykiss) were exposed to radiation doses of 0.250, 0.500, 1, 3, 5, 7, and 9 kGy in a gamma cell. Primers were designed for regions with different lengths of both nuclear and mitochondrial DNA, and each primer was used to amplify the DNA from irradiated samples. The amplicon curves for mitochondrial and nuclear DNA, and the correlations among the curves, were obtained. The Ct values for a 519 bp region of the 18S RNA gene on nuclear DNA correlated appropriately. Radiation doses applied to the fillets were estimated using the standard curve data obtained from the correlation values, and the DNA damage caused by each dose was calculated. As a consequence, a molecular methodology to analyze irradiated fish meat qualitatively and also for the estimation of administered dose was developed. This method allowed analysis of irradiated fish, which had been stored for up to 3 months with a dose limit of approximately 0.5 kGy.

The practical analysis of food: the development of Sakalar quantification table of DNA (SQT-DNA)

Practical and highly sensitive Sakalar quantification table of DNA (SQT-DNA) has been developed for the detection% of species-specific DNA amount in food products. Cycle threshold (Ct) data were obtained from multiple curves of real-time qPCR. The statistical analysis was done to estimate the concentration of standard dilutions. Amplicon concentrations versus each Ct value were assessed by the predictions of targets at known concentrations. SQT-DNA was prepared by using the percentage versus each Ct values. The applicability of SQT-DNA to commercial foods was proved by using sausages containing varying ratios of beef, chicken, and soybean. The results showed that SQT-DNA can be used to directly quantify food DNA by a single PCR without the need to construct a standart curve in parallel with the samples every time the experiment is performed, and also quantification by SQT-DNA is as reliable as standard curve quantification for a wide range of DNA concentrations.

Vibrio vulnificus oysters: pearls and perils

Vibrio vulnificus is a naturally occurring bacterium found ubiquitously in coastal waters. Infection with this organism, which is often associated with eating raw oysters, is the leading cause of seafood-related deaths in the United States. This article reviews the current scientific literature on this potentially lethal pathogen and discusses the prognosis, treatment, and prevention of V. vulnificus infections.

Identification of outer membrane proteins of Vibrio parahaemolyticus and Vibrio alginolyticus altered in response to γ-irradiation or long-term starvation

Vibrio parahaemolyticus and Vibrio alginolyticus were subjected to γ-irradiation (0.5 kGy) or starvation by incubation for 8 months in seawater to study modifications in their outer membrane protein patterns. After treatment, outer membrane protein profiles of starved or γ-irradiated bacteria were found to be altered when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Altered proteins were identified by mass spectrometry (MS and MS/MS) and analyses revealed that OmpU can be considered a starvation stress-induced protein. In addition, expression of OtnA, OmpW, OmpA and peptidoglycan-associated lipoprotein decreased to non-detectable levels in starved cells. Furthermore, MltA-interacting protein MipA appeared under γ-irradiation or starvation conditions. Thus, it can be considered to be a γ-irradiation, long-term starvation stress protein in some vibrios.

Comparison between a TaqMan polymerase chain reaction assay and a culture method for ctx-positive Vibrio cholerae detection

The main objective of the present work was to evaluate a real-time polymerase chain reaction (PCR) method to detect toxigenic Vibrio cholerae in Pangasius hypophthalmus, a freshwater fish cultured mainly in South East Asia. A FDA traditional culture method and a real-time PCR method of the ctx gene were used for detection of V. cholerae in spiked samples of pangasius fish. After an overnight enrichment of samples at 37 degrees C in alkaline peptone water, 2 cfu/25 g of fish was detected with both methods. Although both methods were very sensitive, obtaining results with culture methods may take several days, while real-time PCR takes only a few hours. Furthermore, with traditional methods, complementary techniques such as serotyping, although not available for all serogroups, are needed to identify toxigenic V. cholerae. However, with real-time PCR, toxigenic serogroups are detected in only one step after overnight enrichment.

Alterations of outer membrane proteins and virulence genes expression in gamma-irradiated Vibrio parahaemolyticus and Vibrio alginolyticus

Gamma-irradiation technology sterilizes microorganisms and thereby prevents decay and improves the safety and shelf stability of food products. In this study we treated the foodborne pathogens Vibrio parahaemolyticus and Vibrio alginolyticus with gamma-irradiation (0.5 kGy) to evaluate their adaptative response. Outer membrane protein patterns of irradiated bacteria were found altered when analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. These modifications were manifested by the appearance and/or disappearance of bands as well as in the expression level of certain proteins. In addition, we searched for the presence of eight Vibrio cholerae virulence genes, toxR, toxS, toxRS, ctxA, zot, ace, toxT, and virulence pathogenicity island (VPI), in the genome of investigated strains. The expression of toxR, toxS, VPI, and ace genes in gamma-irradiated bacteria, studied by reverse transcriptase polymerase chain reaction, was altered. These variations were manifested by an increase and/or a decrease in the expression level of tested virulence genes.