AIMS: To evaluate the food safety and spoilage risks associated with psychrotrophic Bacillus cereus group bacteria for the egg product industry and to search for relevant risk markers. METHODS AND ...RESULTS: A collection of 68 psychrotrophic B. cereus group isolates, coming from pasteurized liquid whole egg products, was analysed through a principal component analysis (PCA) regarding their spoilage and food safety risk potentials. The principal component analysis showed a clear differentiation between two groups within the collection, one half of the isolates representing a safety risk and the other half a spoilage risk. CONCLUSIONS: Relevant risk markers were highlighted by PCA, that is (i) for the food safety risk, the presence of the specific 16S rDNA‐1m genetic signature and the ability to grow at 43°C on solid medium and (ii) for the spoilage risk, the presence of the cspA genetic signature. SIGNIFICANCE AND IMPACT OF THE STUDY: This work represents a first step in the development of new diagnostic technologies for the assessment of the microbiological quality of foods likely to be contaminated with psychrotrophic B. cereus group bacteria.
The aim of the present study was (i) to type, by genotypic and phenotypic methods, a collection of psychrotrophic bacteria belonging to the
Bacillus cereus group collected in a farm and in 6 egg ...breaking industries during a period covering a warm and a cold season, and (ii) to characterize the egg product spoilage (growth in liquid whole egg) and the sanitary risk potential (cytotoxic activity on Caco-2 cells and adhesion on stainless steel) of each isolate of the collection. The investigation of specific psychrotrophic and mesophilic signatures together with the study of ability to grow at 6
°C and/or at 43
°C on optimal agar medium allowed highlighting twelve profiles, the major one corresponding to the species
Bacillus weihenstephanensis (46.2% of the collection). The diversity of the profiles depended on the season and on the origin of the isolates. In terms of food spoilage, all the isolates were able to grow at the same level in liquid whole egg and in optimal medium, even at low temperature. Under the same conditions, the cytotoxic activity depended on the isolate, the medium and the temperature. At 10
°C, no isolate was cytotoxic at 10
°C in liquid whole egg and only one, belonging to the
Bacillus weihenstephansensis species, in the optimal medium. All the isolates were able to adhere on stainless steel at various levels, from 2.6
±
0.2
log cfu/cm
2 to 4.9
±
0.1
log cfu/cm
2. A large majority (80.8%) was strongly adhering and could lead to the formation of biofilms in industrial equipments.
Changes in axial stress and refractive index have been measured as a function of the total UV-irradiation fluence during the formation of Bragg gratings in B/Ge- and Sn/Ge-codoped core fibers. For ...the B/Ge-codoped core fiber, a fast development of the type-I grating with a significant increase in refractive index and tensile stress in the fiber core is followed by a slow growth of the type-IIA grating with a gradual decrease of refractive index and tensile core stress. A strong UV-induced reduction of the core stress and a domination of the type-IIA grating are observed for the Sn/Ge-codoped fiber. The index changes of the type-I and type-IIA gratings are believed to be governed by the compaction of the UV-irradiated core network and its dilation, respectively.
In Aspergillus nidulans, the transcriptional activator AlcR mediates specific induction of a number of alc genes. The AlcR DNA‐binding domain is a zinc binuclear cluster that differs from the other ...members of the Zn2Cys6 family in several respects. Of these, the most remarkable is its ability to bind in vitro as a monomer to single sites, whereas only repeated sites (direct or inverted) are necessary and functional in vivo. Deletion of the first five amino acids (following the N‐terminal methionine) upstream of the AlcR zinc cluster or mutation of a single residue, Arg‐6, impairs the AlcR in vitro binding mainly to symmetrical sites. In vivo, the same mutations result in the inability of A. nidulans to grow on ethanol. The alc− phenotype results from a drastic decrease in activation of its own transcription and, in addition, that of the two structural genes, alcA and aldA, required for ethanol oxidation. This defect seems to be correlated to the inability of the Arg‐6 AlcR mutant protein to bind to AlcR palindrome targets, which are essential in the three alc promoters. AlcR shows a unique pattern of binding and of transactivation among the Zn2Cys6 family.
Genome sequence data can be used to analyze genome plasticity by whole genome PCR scanning. Small sized chromosomes can indeed be fully amplified by long‐range PCR with a set of primers designed ...using a reference strain and applied to several other strains. Analysis of the resulting patterns can reveal the genome plasticity. To facilitate such analysis, we have developed GenoFrag, a software package for the design of primers optimized for whole genome scanning by long‐range PCR. GenoFrag was developed for the analysis of Staphylococcus aureus genome plasticity by whole genome amplification in ∼10 kb‐long fragments. A set of primers was generated from the genome sequence of S.aureus N315, employed here as a reference strain. Two subsets of primers were successfully used to amplify two portions of the N315 chromosome. This experimental validation demonstrates that GenoFrag is a robust and reliable tool for primer design and that whole genome PCR scanning can be envisaged for the analysis of genome diversity in S.aureus, one of the major public health concerns worldwide.
Chloroprene was polymerized in emulsion, using a redox system as initiator. With a rosin derivative as surfactant, gel formation was avoided until ca. 70% conversion, but when a reactive maleic ...hemiester surfactant was used, gel could appear at conversions as low as 5%. The purpose of this paper is to show how this problem of early gel formation can be controlled via the flux of radicals entering the particles. Using more initiator leads to shorter polymer chains, a delayed onset of gel formation, and paradoxically to slower polymerizations.
We compared the incorporation of arachidonic acid (AA) and eicosapentaneoic acid (EPA) into phospholipids of non-transformed (NT-) and spontaneously-transformed (T-) rat liver epithelial cells ...(RLEC), and their consequences on DNA-synthesis. In NT-cells, both radioactive fatty acids were preferentially incorporated into phosphatidylcholine (PC). In T-cells, in contrast, AA was predominantly incorporated into phosphatidylethanolamine (PE), whereas EPA remained preferentially incorporated into PC. After pulse labelling, we observed in both cell types a progressive decrease in AA- and EPA-labelled PC associated with an increase in AA- and EPA-labelled PE. Preincubation of NT-cells with increasing concentrations of AA or EPA (0.1 microM to 20 microM) resulted in a concentration-dependent DNA-synthesis stimulation with a stronger effect of AA compared with EPA. In T-cells, the same treatment had no effect on DNA-synthesis.
The presence of Staphylococcus intermedius in food remains unclear because routine laboratory analysis does not discriminate between S. intermedius and Staphylococcus aureus, a major cause of food ...poisoning. Both species share many phenotypic characteristics, including coagulase and thermonuclease production. In both species, some strains can produce enterotoxin and therefore can be the cause of food poisoning outbreaks. Although the ID32 Staph System (bioMerieux, SA, Marcy l'Etoile, France), based on a miniaturized phenotypic characterization, gives satisfactory results for discriminating between these two species, some rapid molecular PCR-based methods have been developed to identify S. aureus specifically, but they do not identify S. intermedius. Here, we developed a rapid, accurate, and discriminative multiplex PCR method that targets species-specific sequences in the nuc gene, which encodes thermonuclease in the two species. The test includes an internal positive control that targets a highly conserved region of 16S ribosomal RNA gene (rDNA). A total of 116 strains were used to validate our test. The test gave no signal on the following Staphylococcus species: S. epidermidis, S. chromogenes, S. hyicus, S. warneri, S. xylosus, S. lentus, and S. sciuri. It allowed a 100% successful discrimination between S. aureus (44 strains tested) and S. intermedius (57 strains) isolated from different origins.
The effects of the gel content of polychloroprene films from latex coalescence on the development of crystallinity and on the dynamic mechanical properties has been studied. The experimental ...techniques were differential scanning calorimetry (DSC), X ray diffraction and small angle diffusion, and finally Dynamic Mechanical Analysis (DMA). The results show that the gel causes a retardation of the crystallinity development and a strong decrease of the mechanical modulus.
Self-clearing transient faults can be considered as precursor of imminent failure of power cables. They exist during a very short duration (few ms) and cannot be detected by conventional protection ...relay. However, they weaken dielectric, causing other transient faults in the future with increasing frequency of occurrence until final insulation breakdown. Thus, imminent failures can be avoided by preventive maintenance if these transient faults are correctly detected and located. This paper presents a method for locating single phase to ground transient faults based on current and voltage measurements at one end of a power cable. Both distance to fault and fault resistance can be estimated by a least square fitting algorithm. Cable capacitances are also considered in our model. The proposed fault locating algorithm has been validated with a small distribution feeder, with two values of grounding impedance.
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