8 research outputs found
Discrimination between Bifidobacterium species from human and animal origin by PCR-restriction fragment length polymorphism
peer reviewedBifidobacteria are normal intestinal flora in humans and animals. The genus Bifidobacterium includes 31 species of significant host specificity. Taking into account their properties, we proposed to use bifidobacteria as fecal contamination indicators. PCR-restriction fragment length polymorphism on the 16S rDNA gene was used to distinguish the different Bifidobacterium species. Sixty-four strains belonging to 13 different species were differentiated from animal or human origin using one or two restriction enzymes. Moreover, the primers used were specifics of the Bifidobacterium genus. Therefore, this method made it possible to determine both the presence of bifidobacteria in a sample and its origin of contamination
A PCR method for detection of bifidobacteria in raw milk and raw milk cheese: comparison with culture-based methods
Bifidobacteria are well known for their beneficial effects on health and are used as probiotics in food and pharmaceutical products. As they form one of the most important groups in both human and animal feces, their use as fecal indicator organisms in raw milk products has recently been proposed. Bifidobacteria species isolated in humans are different from those isolated in animals. It should therefore be possible to determine contamination origin (human or animal). A method of detecting the Bifidobacterium genus was developed by PCR targeting the hsp60 gene. The genus Bifidobacterium was identified by PCR amplification of a 217-bp hsp60 gene fragment. The degenerated primer pair specific to the Bifidobacterium genus used was tested for it specificity on 127 strains. Sensitivity was measured on artificially contaminated samples. Food can however be a difficult matrix for PCR testing since it contains PCR inhibitors. So an internal PCR control was used. An artificially created DNA fragment of 315 bp was constructed. The PCR detection method was tested on raw milk and cheese samples and compared with three culture-based methods, which comprised enrichment and isolation steps. The enrichment step used Brain Heart Infusion medium with propionic acid, iron citrate, yeast extract, supplemented with mupirocin (BHMup) or not (BH) and the isolation step used Columbia blood agar medium, supplemented with mupirocin (CMup) or not (C). The method using mupirocin at both enrichment and isolation steps and the PCR method performed from the culture in BHMup enrichment medium were shown to be the most efficient. No significant difference was observed in raw milk samples between PCR from BHMup and the culture-based method BHMup/CMup, while a significant difference was noticed between the same methods in raw milk cheese samples, which would favor using PCR. The results suggested that PCR on the hsp60 gene was convenient for a rapid detection of bifidobacteria in raw milk and raw milk cheese samples and that bifidobacteria always present throughout raw milk cheese production could be efficiently used as fecal indicators
ARYL HYDROCARBON RECEPTOR-MEDIATED AGONIST/ANTAGONIST/SYNERGIC ACTIVITIES OF FOOD POLYPHENOLS ARE SPECIES- AND TISSUE-DEPENDENT
Study of the flavonoids effect on the AhR-dependent transcription using reporter gene assays
Time-, species- and tissue-dependent activity profiles of food flavonoids on the activation of the aryl hydrocarbon pathway
peer reviewe
Reporter gene assays to assess modulations of AhR and steroid receptors pathways by « active ingredients » from food supplements
Food flavonoid aryl hydrocarbon receptor-mediated agonistic/antagonistic/synergic activities in human and rat reporter gene assays
Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor mediating the
adverse effects of dioxins and polycyclic aromatic hydrocarbons (PAHs). In this study, we
investigated the genetic-, time-, dose-, species- and tissue-dependent AhR-mediated agonistic/
antagonistic activities of three food flavonoids: quercetin, chrysin and genistein.
To that end, four stably transfected cell lines were used in cell-based luciferase reporter
gene assays: three lines were transformed with the ptKLuc vector harbouring four dioxinresponsive
elements (DREs) upstream of the thymidine kinase promoter and the luciferase
gene (HepG2-Luc, T-47D-Luc and H4IIE-ULg). The fourth is a patented cell line transformed
with a different construct: H4IIE DR-CALUX®. Both H4IIE cells were compared for their
genetic construction. Human hepatoma (HepG2-Luc) and human breast tumour (T-47D-Luc)
cells were compared for tissue-dependent effects. Rat hepatoma (H4IIE-ULg) and human
hepatoma (HepG2-Luc) cellswere compared for species-dependent activities.We concluded
that quercetin, chrysin and genistein act in a time-, dose-, species- and tissue-specific way.
For example, genistein displayed agonistic activities when exposed to rat hepatoma cells
during 6h but not after 24 h. Flavonoids displayed agonistic/antagonistic activities in human
breast tumour cells, depending on the exposure time, while in human hepatoma cells, only
antagonistic activities of flavonoids were measured. In addition, we report, in all the cells, a
synergy between an isoflavone and two food contaminants; the 2,3,7,8-tetrachlorodibenzop-
dioxin and 3-methylcholanthrene, a PAH. In rat cells, this synergy occurred when cells
were exposed to flavonoids and contaminant for 6h, while it was observed in human cells
only after 24 h