Biomedical subjects

Régine Talon

Publications and source records attributed to Régine Talon.

8 recordsLinked to original sources

PubMed2007

A new device for rapid evaluation of biofilm formation potential by bacteria.

This work describes the implementation of a new assay named the BioFilm Ring Test to evaluate the ability of bacteria to form biofilms. This assay is based on the immobilisation (or not) of magnetic beads embedded by bacterial aggregates or mats (patented concept). It is realised on modified polystyrene 96-wells microtiter plates with individual 8-wells slides. The kinetic of biofilm formation of four bacterial species, Listeria monocytogenes, Escherichia coli, Staphylococcus carnosus and Staphylococcus xylosus was evaluated with this new device by comparison with the standard crystal violet staining method of sessile cells. In parallel, the biofilm growth was visualized by Scanning Electron Microscopy (SEM) observations. The BioFilm Ring Test gave similar but faster results than the crystal violet method. Moreover, the new assay was easier to implement, more reproducible and allowed high throughput screenings due to limited manipulations (no washing and staining steps) and rapid and accurate measurements of magnetic bead immobilisation by sessile bacterial cells.

Bacteria↗

PubMed2007

Physical and genetic map of the Staphylococcus xylosus C2a chromosome.

Staphylococcus xylosus is a ubiquitous bacterium frequently isolated from mammalian skin and occurring naturally on meat and dairy products. A physical and genetic map of the S. xylosus C2a chromosome was constructed by pulsed-field gel electrophoresis analysis after digestion with AscI, ApaI, I-CeuI, SfiI and SmaI enzymes and hybridization analysis. The chromosome size was estimated to be 2868+/-10 kb. Thirty-three genetic markers were mapped. The probable origin of replication (oriC) was positioned. Six rrn loci were located, and their orientation was determined. The chromosomes of six additional S. xylosus strains were also analysed by I-CeuI digestion, and an intraspecies diversity of the chromosome size and the number of rrn operons was shown.

Bacterial Proteins↗

PubMed2006

Effect of industrial and natural biocides on spoilage, pathogenic and technological strains grown in biofilm.

This study aimed at investigating bactericide solutions effective on spoilage and pathogenic bacteria while preserving technological bacteria. Two compounds of essential oil (thymol and eugenol), one essential oil of Satureja thymbra and two industrial biocides (PE 270-30, Brillo) were tested on technological strains (Staphylococcus equorum, Staphylococcus succinus and Lactobacillus sakei) grown in monoculture biofilm and on a mixed biofilm of pathogenic bacteria (Staphylococcus aureus, Listeria monocytogenes) and spoilage bacteria (Pseudomonas fragi, Escherichia coli). Biofilm cultures were performed in glass fibre filters for 24h at 20 degrees C before application of biocides. Thymol and eugenol had no effect on the mixed biofilm. S. thymbra (2%) was highly effective on spoilage strains (5 log reduction), and S. equorum (4 log reduction) was moderately effective on pathogens (2.3 log reduction) and not effective on S. succinus and L. sakei (0.5 log reduction). PE-270-30 with 10% Na((2))SO((4)) decreased spoilage bacteria (5.1 log reduction), maintained the technological bacteria, but did not reduce the pathogens. The disinfectant Brillo (3%) killed all the strains. These results showed the difficulty in obtaining a biocide that is effective in destroying spoilage and pathogenic bacteria while preserving technological bacteria. Essential oils could be a good alternative for eradicating spoilage bacteria in the food environment where they are often found at high levels.

Anti-Infective Agents↗

PubMed2006

Staphylococcal community of a small unit manufacturing traditional dry fermented sausages.

The level and the diversity of the staphylococcal community occurring in the environment and meat products of a small unit manufacturing traditional dry fermented sausages were investigated at two seasons: winter and spring. Gram-positive cocci were enumerated and a collection of 412 Staphylococcus isolates was made. Multiplex PCR, pulse-field gel electrophoresis (PFGE) and sequencing of the sodA gene were used to identify and characterize the isolates. High counts of Staphylococcus were found in final traditional sausages, reaching about 6 log CFU/g in winter and about 8 log CFU/g in spring. In the environment, the counts varied from 2 log to 7 log/100 cm(2), the higher colonisation being observed on the surface of the drying and cold rooms, cutting tables and the butcher's block. The combination of the three methods allowed the identification of seven species of Staphylococcus in spring and five in winter. S. equorum and S. succinus dominated both in environment and in meat products, 49% and 33% of the isolates, respectively. The other identified species were in decreasing order S. saprophyticus (6%), S. xylosus (5%), S. carnosus (5%), S. simulans (1%) and S. warneri (1%). The two species S. xylosus and S. carnosus were sporadically isolated during the spring. PFGE allowed the assignment of S. equorum to eight pulsotypes showing a wide diversity among this species. But the entire environment and the meat products were dominated by one pulsotype. For S. succinus, three pulsotypes were found with one dominant mainly isolated during the spring sampling. This study highlighted the diversity of staphylococci isolated in the environment and the meat products of a small processing unit manufacturing traditional dry fermented sausages. The S. equorum and S. succinus species rarely described in meat products and never in the environment had great capacity to colonise the entire small processing unit and the meat products.

Animals↗

PubMed2003

Preliminary characterization of beta-decarboxylase activities in Staphylococcus carnosus 833, a strain used in sausage fermentation.

In sausage, Staphylococcus carnosus increases the levels of methyl ketones which could arise from incomplete beta-oxidation of fatty acids followed by a decarboxylation. The objective of this work was to characterize the beta-decarboxylase activities in cell-free extract. By using different substrates, at least two kinds of beta-decarboxylase activities were shown: an acetoacetate-like and an oxaloacetate-like. The first one leads to the production of ketones from ethylbutyryl acetate or acetoacetic acid. The activity was optimal at pH 6.0, stimulated by pyridoxal phosphate but ethylenediamine tetraacetic acid (EDTA), NaCl, iodoacetate and curing additives were inhibitory. The second decarboxylase activity leads to the production of pyruvic acid from oxaloacetic acid. This activity was optimal at pH 5.0 and stimulated by divalent ions and biotin.

Biotin↗

PubMed2003

Development of specific PCR primers for a rapid and accurate identification of Staphylococcus xylosus, a species used in food fermentation.

Twenty-seven Staphylococcus strains isolated from food and food environments were assigned to Staphylococcus xylosus by API-Staph system. But only seven isolates had similar patterns to this species when compared to the pulse-field gel electrophoresis patterns of 12 S. xylosus strains. To perform a rapid identification of the S. xylosus species, a random amplified polymorphic DNA product of 539-bp shared by all of the S. xylosus strains was used to design a pair of primers. These primers were species-specific for S. xylosus when tested by PCR on 21 staphylococci species. This specific PCR assay confirms the identification of the seven isolates identified by PFGE to S. xylosus. In conclusion, we developed specific PCR primers for a rapid and accurate identification of the S. xylosus species.

DNA Primers↗

PubMed2002

Characterisation of the katA gene encoding a catalase and evidence for at least a second catalase activity in Staphylococcus xylosus, bacteria used in food fermentation.

The catalase gene katA of Staphylococcus xylosus was cloned. It encodes a protein of 494 amino acids with a molecular mass of 56.9 kDa, closely related to monofunctional catalases. A katA mutant still showed a relatively high catalase activity demonstrating that S. xylosus possesses more than one enzyme. By Southern blot analysis using a katA probe, a second genetic locus distinct from katA was detected that probably contained the additional catalase gene. To analyse katA expression, a transcriptional fusion of the katA promoter region to a promoterless beta-galactosidase gene was integrated into the genome of S. xylosus. katA expression is induced upon entry into stationary phase, by oxygen and hydrogen peroxide. Iron and manganese depletion induced katA transcription. Comparing the resistance of S. xylosus wild-type and the katA mutant strain to hydrogen peroxide clearly showed that KatA is essential for S. xylosus to cope with hydrogen peroxide stress. Therefore, S. xylosus has at least two differentially expressed catalases.

Blotting, Southern↗

PubMed2002

Development of an enzymatic method to quantify methyl ketones from bacterial origin.

Methyl ketones are detected in dry fermented sausages in which they contribute to the cured aroma. They have been associated with the inoculation of Staphylococcus carnosus used as starter culture. To evaluate the ability of bacterial starters to produce methyl ketones it was necessary to develop a rapid method. The method consists of a reaction catalyzed by a commercial NADPH-dependent alcohol dehydrogenase that reduces the 2-pentanone to its secondary alcohol. The linearity, the specificity, and the robustness were studied. Its accuracy was confirmed by comparison with the gas chromatography technique. Finally, the method was validated on biological samples such as the 2-pentanone produced by Staphylococcus carnosus. The enzymatic method offers some advantages over the gas chromatography, as it is faster, simpler, and inexpensive, guaranteeing an effective way to assess bacterial ketone production.

Alcohol Dehydrogenase↗