Toxin production in a rare and genetically remote cluster of strains of the Bacillus cereus group

<p>Abstract</p> <p>Background</p> <p>Three enterotoxins are implicated in diarrhoeal food poisoning due to <it>Bacillus cereus</it>: Haemolysin BL (Hbl), Non-haemolytic enterotoxin (Nhe), and Cytotoxin K (CytK). Toxin gene profiling and assays for detection of toxin-producing stains have been used in attempts to evaluate the enterotoxic potential of <it>B. cereus </it>group strains. <it>B. cereus </it>strain NVH 391/98, isolated from a case of fatal enteritis, was genetically remote from other <it>B. cereus </it>group strains. This strain lacked the genes encoding Hbl and Nhe, but contains CytK-1. The high virulence of this strain is thought to be due to the greater cytotoxic activity of CytK-1 compared to CytK-2, and to a high level of <it>cytK </it>expression. To date, only three strains containing <it>cytK-1 </it>have been identified; <it>B. cereus </it>strains NVH 391/98, NVH 883/00, and INRA AF2.</p> <p>Results</p> <p>A novel gene variant encoding Nhe was identified in these three strains, which had an average of 80% identity in protein sequence with previously identified Nhe toxins. While culture supernatants containing CytK and Nhe from NVH 391/98 and INRA AF2 were highly cytotoxic, NVH 883/00 expressed little or no CytK and Nhe and was non-cytotoxic. Comparative sequence and expression studies indicated that neither the PlcR/PapR quorum sensing system, nor theYvrGH and YvfTU two-component systems, were responsible for the observed difference in toxin production. Additionally, phylogenetic analysis of 13 genes showed that NVH 391/98, NVH 883/00, and INRA AF2 comprise a novel cluster of strains genetically distant from other <it>B. cereus </it>group strains.</p> <p>Conclusion</p> <p>Due to its divergent sequence, the novel <it>nhe </it>operon had previously not been detected in NVH 391/98 using PCR and several monoclonal antibodies. Thus, toxigenic profiling based on the original <it>nhe </it>sequence will fail to detect the toxin in this group of strains. The observation that strain NVH 883/00 carries <it>cytK-1 </it>but is non-cytotoxic indicates that the detection of this gene variant is not a sufficient criterion for identification of highly cytotoxic strains. The presence of the novel <it>nhe </it>operon and the <it>cytK-1 </it>gene variant in this cluster of strains reflect their phylogenetically remote relationship towards other <it>B. cereus </it>group strains.</p

Physico-chemical modifications of the interactions between hemp fibres and a lime mineral matrix: impacts on mechanical properties of mortars

International audienceIn order to understand the physico-chemical mechanisms governing interactions between hemp fibres and a lime-based mineral matrix, the consequences of various chemical treatments onto hemp fibres characteristics were measured using scanning electron microscopy, thermal analysis, X-ray diffraction and FTIR spectroscopy. Secondly, effects of these treatments on the mechanical properties of lime mortars incorporating the chemically modified fibres were evaluated using 3 point bending tests. NaOH and EDTA treatments increase the crystallinity index of hemp fibres and increase the experimental rigidity of lime/natural fibres mortars. Treatments with polyethylene imine and a saturated lime solution do not induce any significant changes onto the mechanical properties. These results show that some specific chemical treatments have an impact onto the hemp/lime interfaces quality. The elaborated composite materials exhibit a higher rigidity and an improvement of the matrix /fibre charge transfer. However, the rupture stress is only slightly modified due to a relatively low fibre volumic content (10 %)

Detection of embryo mortality and hatch using thermal differences among incubated chicken eggs

Accurate diagnosis of both the stage of embryonic mortality and the hatch process in incubated eggs is a fundamental component in troubleshooting and hatchery management. However, traditional methods disturb incubation, destroy egg samples, risk contamination, are time and labour-intensive and require specialist knowledge and training. Therefore, a new method to accurately detect embryonic mortality and hatching time would be of significant interest for the poultry industry if it could be done quickly, cheaply and be fully integrated into the process. In this study we have continuously measured individual eggshell temperatures and the corresponding micro-environmental air temperatures throughout the 21 days of incubation using standard low-cost temperature sensors. Moreover, we have quantified the thermal interaction between eggs and air by calculating thermal profile changes (temperature drop time, drop length and drop magnitude) that allowed us to detect four categories of egg status (infertile/early death, middle death, late death and hatch) during incubation. A decision tree induction classification model accurately (93.3%) predicted the status of 105 sampled eggs in comparison to the classical hatch residue breakout analyses. With this study we have provided a major contribution to the optimisation of incubation processes by introducing an alternative method for the currently practiced hatch residue breakout analyses.status: publishe

Guidance on the assessment of the toxigenic potential of <em>Bacillus</em> species used in animal nutrition

Bacillus species are used in animal production directly as microbial feed additives or as the source of other feed additives, notably enzymes. The principal safety concern for consumers and, to a lesser extent livestock, associated with Bacillus is a capacity for toxin production.  However, the capacity for toxin production and the nature of the toxins produced is unevenly distributed over the genus, occurring frequently in some species and more rarely in others. In principle, the selection of strains belonging to the B. cereus taxonomic group for direct use in animal production is considered inadvisable. If, however, they are proposed then the full genome should be sequenced and a bioinformatic analysis made to search for genes coding for enterotoxins and cereulide synthase. If there is evidence of homology, the non-functionality of the genes (e.g. mutation, deletion) must be demonstrated. For other species, concerns appear to be associated to the production of surfactin like-lipopeptides, although the relation between the presence of these compounds and/or other toxic factors and the risk of illness in human has not yet been established. In the absence of animal models shown to be able to distinguish hazardous from non hazardous strains, the FEEDAP Panel relies on the use of in vitro cell-based methods to detect evidence of a cytotoxic effect. Such tests should be made with culture supernatants since the concentration of cells obtained in a broth culture would always exceed that found in animal food products. If the strain proves to be cytotoxic it is not recommended for use

A multicenter randomized phase II study of sequential epirubicin/cyclophosphamide followed by docetaxel with or without celecoxib or trastuzumab according to HER2 status, as primary chemotherapy for localized invasive breast cancer patients

International audienceTo assess anti-tumor activity of sequential epirubicin/cyclophosphamide followed by docetaxel with the randomized addition of celecoxib in HER2 negative patients or trastuzumab in HER2 positive patients. From May 2004 till October 2007, 340 patients with stage II and III breast adenocarcinoma, ineligible for breast conserving surgery, received eight sequential three weekly cycles of EC-D [epirubicin (75 mg/m)–cyclophosphamide (750 mg/m) for four cycles followed by docetaxel (100 mg/m) for four cycles]. HER2-negative patients ( = 220) were randomized to receive concomitantly with docetaxel celecoxib 800 mg/day during cycles 5–8 or no additional treatment, while HER2-positive patients confirmed by FISH ( = 120) were randomized to trastuzumab concomitant to docetaxel (8 mg/kg then 6 mg/kg IV every 3 weeks) or no additional preoperative treatment. In the HER2 negative group, pCR (grade 1 and 2 of Chevallier's classification) was observed in 11.5 and 13% of patients treated without and with neoadjuvant Celecoxib, respectively. In the HER2 positive group, pCR rate reached 26% in those who received neoadjuvant trastuzumab versus 19% in the others. There was no unexpected toxicity, no cardiac toxicity, and no toxic death. Triple negative breast cancers experience the highest pCR rate of 30%. Celecoxib is not likely to improve pCR rates in addition to EC-D in patients with HER2-negative tumor. In HER2-positive tumor patients, trastuzumab added to ECD leads to increased pCR rates. It was the only combination to deserve further study according to the two-stage Fleming's design used in this trial

Full reciprocal-space mapping up to 2000 K under controlled atmosphere: the multipurpose QMAX furnace

We acknowledge the ESRF and the French Collaborating Research Group (F-CRG) for provision of synchrotron radiation facility beamtime. H. Song is thanked for his work on the preliminary thermomechanical calculations and the general sizing of the furnace. The building of the furnace has been realized under the technical supervision of D. de Barros. The experiments on the sapphire vicinal surfaces and on the IUCr zirconia powder were realized with the valuable help of C. Matringe (IRCER) and J. B. Marijon (PIMM), respectively. The authors are thankful to I. Cabodi and O. Bories (Saint-Gobain CREE) for the supply of the bulk-zirconia-based materials. M. Huger and F. Gouraud from the IRCER laboratory and T. O¨ rs and V. Michel from the PIMM labora-tory are strongly thanked for their involvement during these experiments. The oxidation experiments were realized in the frame of a research program funded by the CEA Paris–Saclay Centre in collaboration with R. Guillou, M. Lesaux, D. Menut and J. L. Bechade, who are also gratefully acknowledged.A furnace that covers the temperature range from room temperature up to 2000 K has been designed, built and implemented on the D2AM beamline at the ESRF. The QMAX furnace is devoted to the full exploration of the reciprocal hemispace located above the sample surface. It is well suited for symmetric and asymmetric 3D reciprocal space mapping. Owing to the hemispherical design of the furnace, 3D grazing-incidence small- and wide-angle scattering and diffraction measurements are possible. Inert and reactive experiments can be performed at atmospheric pressure under controlled gas flux. It is demonstrated that the QMAX furnace allows monitoring of structural phase transitions as well as microstructural evolution at the nanoscale, such as self-organization processes, crystal growth and strain relaxation. A time-resolved in situ oxidation experiment illustrates the capability to probe the high-temperature reactivity of materials.The QMAX furnace has been designed and built as part of the QMAX Project No. ANR-09-NANO-031 funded by the French National Research Agency (ANR). Experiments on the bulk-zirconia-based samples were done in the frame of the ASZTECH research program funded by the ANR (ANR-12-RMNP-0007)