Application of propidium monoazide-qPCR to evaluate the ultrasonic inactivation of Escherichia coli O157:H7 in fresh-cut vegetable wash water.

The efficacy of sanitizing technologies in produce or in vegetable wash water is generally evaluated by plate count in selective media. This procedure is time consuming and can lead to misinterpretations because environmental conditions and sanitizing processes may affect bacterial growth or culturable capability. Thus, the aim of this study was to determine the applicability of a propidium monoazide real-time PCR (PMA-qPCR) method to monitor the inactivation by ultrasound treatment of foodborne bacteria in fresh-cut vegetable wash water. To this aim, lettuce wash water was artificially inoculated with Escherichia coli O157:H7 (106 CFU/mL) and treated by means of a continuous ultrasonic irradiation with a power density of 0.280 kW/L. Quantification data obtained by PMA-qPCR and plate counts were statistically similar during the viability reduction of 99.996% which corresponds to 4.4 log reductions. Further reductions of E. coli O157:H7 were not detected by the PMA-qPCR method due to the limit of detection of this technique (20 CFU/mL). Inactivation data obtained by both techniques successfully fitted a linear model, giving no significant differences in kinetic parameters. These results indicate that the PMA-qPCR method is a suitable technique for evaluating ultrasonic disinfection of vegetable wash water, being able to distinguish between live and dead bacteria.

4-Hydroxydibenzyl: a novel metabolite from the human gut microbiota after consuming resveratrol.

Resveratrol (RSV) was known to be metabolised by the gut microbiota to dihydroresveratrol, lunularin (LUNU), and (or) 3,4'-dihydroxy-trans-stilbene (DHST). We describe here for the first time that LUNU can be further dehydroxylated, but only at the 3-position, to yield 4-hydroxydibenzyl, a novel metabolite found in human urine after RSV intake in 41 out of 59 healthy participants. In contrast, DHST was not further dehydroxylated, and thus, 4-hydroxy-trans-stilbene was not detected as a gut microbial metabolite of RSV. Faecal in vitro incubations confirmed the in vivo results.

The gut microbiota urolithin metabotypes revisited: the human metabolism of ellagic acid is mainly determined by aging.

Understanding individuals' response to dietary bioactives is crucial for personalized nutrition. We report here for the first time in a Caucasian cohort (5-90 years, n = 839) that aging is the main factor that determines the gut microbiota involved in the ellagic acid-ellagitannin metabolism (urolithin metabotypes), with potential consequences for human health.

Consumption of pomegranate decreases plasma lipopolysaccharide-binding protein levels, a marker of metabolic endotoxemia, in patients with newly diagnosed colorectal cancer: a randomized controlled clinical trial.

Gut microbiota dysbiosis alters the intestinal barrier function, increases plasma lipopolysaccharide (LPS) levels, which promotes endotoxemia, and contributes to the onset and development of colorectal cancer (CRC). We report here for the first time the reduction of plasma LPS-binding protein (LBP) levels, a marker of endotoxemia, after pomegranate consumption in newly diagnosed CRC patients.

Simultaneous detection of the main black aspergilli responsible for ochratoxin A (OTA) contamination in grapes by multiplex real-time polymerase chain reaction.

This paper reports a duplex real-time polymerase chain reaction (PCR) assay for the simultaneous detection of members of the Aspergillus niger aggregate and A. carbonarius, which are the main responsible species for ochratoxin A (OTA) contamination in grapes. This single tube reaction targets the beta-ketosynthase and the acyl transferase domains of the poliketide synthase of A. carbonarius and the A. niger aggregate, respectively. Melting curve analysis using a SYBR Green I real-time PCR approach showed characteristic T(m)-values demonstrating the specific, efficient and balanced amplification of the two PCR fragments. Subsequently, a TaqMan real-time PCR approach was settled, using 6-carboxy-fluorescein group (FAM) and VIC-labelled specific probes for automated detection. Results indicated no differences in sensitivity when using either the two sets of primers and probes in separate or in the same reaction. However, when both targets are in very different amounts, there is a preferential amplification of the target which is in more concentration. CT-values obtained in the presence of grape DNA were very similar to those observed when only fungal purified DNA was present, indicating that the grape DNA does not interfere in the real-time PCR reaction. This procedure provides a fast and accurate tool to monitor, in a single reaction, the presence of OTA-producing species in grapes which, to some extent, will facilitate OTA contamination surveys to guarantee food safety in the wine industry.

Potential microbial risk factors related to soil amendments and irrigation water of potato crops.

AIMS: This study assesses the potential microbial risk factors related to the use of soil amendments and irrigation water on potato crops, cultivated in one traditional and two intensive farms during two harvest seasons. METHODS AND RESULTS: The natural microbiota and potentially pathogenic micro-organisms were evaluated in the soil amendment, irrigation water, soil and produce. Uncomposted amendments and residual and creek water samples showed the highest microbial counts. The microbial load of potatoes harvested in spring was similar among the tested farms despite the diverse microbial levels of Listeria spp. and faecal coliforms in the potential risk sources. However, differences in total coliform load of potato were found between farms cultivated in the autumn. Immunochromatographic rapid tests and the BAM's reference method (Bacteriological Analytical Manual; AOAC International) were used to detect Escherichia coli O157:H7 from the potential risk sources and produce. Confirmation of the positive results by polymerase chain reaction procedures showed that the immunochromatographic assay was not reliable as it led to false-positive results. CONCLUSIONS: The potentially pathogenic micro-organisms of soil amendment, irrigation water and soil samples changed with the harvest seasons and the use of different agricultural practices. However, the microbial load of the produce was not always influenced by these risk sources. Improvements in environmental sample preparation are needed to avoid interferences in the use of immunochromatographic rapid tests. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential microbial risk sources of fresh produce should be regularly controlled using reliable detection methods to guarantee their microbial safety.