Biomedical subjects

Anne-Marie Revol-Junelles

Publications and source records attributed to Anne-Marie Revol-Junelles.

8 recordsLinked to original sources

PubMed2006

A selective enumeration medium for Carnobacterium maltaromaticum.

A selective medium was proposed for isolating the species Carnobacterium maltaromaticum from cheeses. This medium, named CM, was elaborated using combinations of three antibiotics (gentamicin, nalidixic acid, vancomycin) and alkaline pH value (8.8). An experimental design (Doehlert matrix) was drawn up to optimize the experimental conditions of the preparation of the medium. Based on the TS-YE agar medium, it contained 3.5 mg L(-1) of vancomycin, 5.0 mg L(-1) of gentamicin, and 20 mg L(-1) of nalidixic acid. The incubation time was 36 to 48 h at 25 degrees C. The selectivity of this medium was tested against bacterial strains present in the dairy industry and controlled by the PCR method. Thanks to this medium, it was easy to detect C. maltaromaticum and to follow this species in the cheese-making process.

Anti-Bacterial Agents↗

PubMed2005

Quantitative polymerase chain reaction used for the rapid detection of Carnobacterium species from French soft cheeses.

An identification method by PCR, specific to the Carnobacterium genus, was optimised by testing it on 28 bacterial strains. Primers from the literature were tested to differentiate Carnobacterium strains present among various bacterial species. The DNA of Carnobacterium species (C. alterfunditum, C. divergens, C. funditum, C. gallinarum, C. inhibens, C. maltaromaticum, C. mobile, C. viridans), specifically amplified by the Cb1-Cb2R primer couple at a hybridization temperature of 69 degrees C, gave only one band of 340 bp. The validation of this technique was carried out on a French soft cheese made with pasteurised milk inoculated with C. maltaromaticum LMA 28. Using classical PCR, detection was not possible for decimal dilutions of the cheese above 1 g L(-1). With Sybr Green I real time PCR, the specificity of the reaction was confirmed by the T(m) value. The standard curve constructed using the main threshold cycle and various concentrations of C. maltaromaticum LMA 28 (ranging from 10(0) to 10(8) cfu mL(-1)) showed good linearity and a sensitivity limit of > or = 10(4) cfu g(-1) of cheese. This technique was applied on commercially available cheeses made from raw cow's milk. The Sybr Green I real time PCR method constitutes an effective and easy-to-perform method to quantify Carnobacterium sp. in cheese.

Animals↗

PubMed2005

Behavior of Escherichia coli cells and Bacillus cereus spores on poplar wood crates by impedance measurements.

Dry poplar wood crates and glass surfaces (bottoms of Pyrex flasks) were contaminated with aqueous suspensions of Escherichia coli Collection de l'Institut Pasteur (CIP) 54.8 cells or Bacillus cereus CIP 78.3 spores. After different periods of storage at 25 degrees C, the number of cells still present on both surfaces was determined by impedance microbiology. The physical and chemical properties of the wood greatly and rapidly decreased the number of cells. After 4 h of contact time, B. cereus residual metabolic activity corresponded to less than 10% of the initial inoculum level. With a low inoculum level of 2.4 x 10(2) E. coli cells, sterility of the wood was obtained after a contact time of 24 h. With a higher inoculum level of 10(6) E. coli cells, only a few viable bacteria, corresponding to the metabolic activity of four cells, could be recovered after a prolonged contact time of 145 h. Conversely, under the same conditions of storage, when bacteria were deposited on inert and nonporous materials such as glass surfaces, growth occurred. After 24 h of contact time at 25 degrees C, bacterial populations were about 10(9) cells for E. coli and 10(7) cells for B. cereus. Under our experimental conditions after a prolonged contact time, wood exhibited growth-inhibiting properties and cells were no longer metabolically active. These results indicate that the potential for cross-contamination of foods stored directly in contact with previously contaminated poplar wood crates is low under our experimental conditions.

Bacillus cereus↗

PubMed2004

Cell envelope analysis of insensitive, susceptible or resistant strains of Leuconostoc and Weissella genus to Leuconostoc mesenteroides FR 52 bacteriocins.

Mesenterocins 52A and 52B belong to class II of lactic acid bacteria bacteriocins. To study susceptibility, insensitivity and resistance to these mesenterocins, four wild-type bacterial strains and four resistant strains, all from Leuconostoc or Weissella genus, were compared. Several cell envelope features were investigated: susceptibilities to antibiotics and to lysozyme, cell morphology and membrane phospholipids contents. The strain insensitive to the two mesenterocins appeared to be resistant to lysozyme and exhibited the highest resistance to antibiotics. Resistant strains displayed cell morphology modifications, several increases in antibiotic resistance and modifications in lysozyme susceptibility. Moreover, mesenterocin 52A-resistant strains displayed modifications in their membrane phospholipids, leading to a more cationic membrane. Insensitivity and resistance of Leuconostoc or Weissella strains seem to be due to various minor modifications of the membrane and/or of the cell wall.

Anti-Bacterial Agents↗

PubMed2004

Synergistic mode of action of mesenterocins 52A and 52B produced by Leuconostoc mesenteroides subsp. mesenteroides FR 52.

Few studies have been published on the effects of two bacteriocins combinations and particularly on combinations of two bacteriocins with different structures produced by the same strain. In this work, the actions of mesenterocin 52A (class IIa) and mesenterocin 52B (class II), produced by Leuconostoc mesenteroides subsp. mesenteroides FR 52, were studied on strains susceptible to only one bacteriocin or to both. In broth, combination of mesenterocins enhanced the adaptation time of the strain susceptible to the both mesenterocins (48 h vs 17 h with only one bacteriocin). In agar medium, mesenterocins displayed, as expected, a synergistic effect on this strain (FIC(index) < 1), but also on the two strains susceptible to only one mesenterocin. This original result was probably due to membrane composition modifications induced by the mesenterocin that enhanced bacteriocin action. Thus, this hurdle technique seems to be interesting in food preservation in terms of minimizing bacteriocin concentrations.

Bacterial Proteins↗

PubMed2002

Characterization of anti-Listeria monocytogenes bacteriocins from Enterococcus faecalis, Enterococcus faecium, and Lactococcus lactis strains isolated from Raïb, a Moroccan traditional fermented milk.

Seventy-four samples of raïb, a Moroccan traditional fermented milk, were screened for their anti-Listeria monocytogenes activity. Nine lactic acid bacteria with antilisterial activity were isolated and identified as Lactococcus lactis [4], Enterococcus faecium [4], and E. faecalis [1]. Antibacterial spectra, determined against 45 target strains, led to the selection of four antibacterial-producing strains, which were further characterized. Their anti-microbial agents, inactivated by one or more proteases, were designed as bacteriocins. Lactococcin R9/2 and R10/1 showed the broadest range of inhibitory action. Anti-bacterial spectra and physico-chemical properties suggest that these bacteriocins were similar to nisin. Enterocin R69 had a specificity of action against Listeria spp., whereas Enterocin R18 had a broad spectrum of activity. Lc. lactis R9/2 and E. faecalis R18 were able to coagulate sterilised UHT milk at 30 degrees C in 24 h and induced a 2 log reduction in L. monocytogenes ATCC 15313 population.

Animals↗

PubMed2002

Variations in the membrane fatty acid composition of resistant or susceptible Leuconostoc or Weissella strains in the presence or absence of Mesenterocin 52A and Mesenterocin 52B produced by Leuconostoc mesenteroides subsp. mesenteroides FR52.

Mesenterocins 52A (Mes52A) and 52B (Mes52B) are antimicrobial peptides produced by Leuconostoc mesenteroides subsp. mesenteroides FR 52. Mes52A is a class IIa bacteriocin of lactic acid bacteria with a broad spectrum of activity. Mes52B is an atypical class II bacteriocin with a narrow spectrum of activity. Four Leuconostoc and Weissella wild-type strains were selected for their susceptibility or insensitivity to these mesenterocins. Four strains resistant to Mes52A or Mes52B were generated from the three susceptible wild-type strains by increasing bacteriocin concentrations in culture media. These resistant strains were at least 30 times more resistant than the wild-type strains. No cross-resistance to Mes52A and Mes52B was observed in these strains. No significant differences in membrane fatty acid composition were observed among the three susceptible wild-type strains and the four resistant strains cultured in MRS broth. Thus, the mesenterocin resistance is unlikely to be due to changes in membrane fatty acid composition. When cultured with Mes52A or Mes52B, the membranes of insensitive and resistant strains contained more saturated fatty acids (1 to 10% more) and less unsaturated fatty acids (3 to 6% less), resulting in a more rigid membrane. Thus, the presence of mesenterocin in the culture media of insensitive or resistant strains induced a significant increase in saturated fatty acid contents and a decrease in unsaturated fatty acid contents. Weissella paramesenteroides DSM 20288BR, resistant to Mes52B, responded atypically, probably due to the production of an inhibitor.

Bacteriocins↗

PubMed1998

Sequence and structural relationships of leucocins A-, B- and C-TA33a from Leuconostoc mesenteroides TA33a.

Amino acid sequences of two of the three bacteriocins from Leuconostoc mesenteroides TA33a were determined and their sequence-structure relationships investigated. Leucocin B-TA33a consists of 31 amino acid residues, with a molecular mass of 3466 Da. Leucocin B-TA33a does not belong to the pediocin family of bacteriocins, but shares 62% homology with mesenterocin 52B. A partial sequence of 36 amino acids of leucocin C-TA33a (4598 Da) was determined. Leucocin C-TA33a belongs to the class II bacteriocins having the consensus YGNGV motif. The third bacteriocin, leucocin A-TA33a, is identical to leucocin A-UAL 187. Circular dichroism spectra of the leucocins in aqueous solution and micellar SDS indicated that they undergo a structural transition when in a membrane-mimicking environment. Theoretical predictions from circular dichroism data suggest that leucocins A-, B- and C-TA33a adopt a beta-structure (48%) in membrane-mimicking environments. Sequence alignments and secondary structure predictions for the N-terminus of leucocins A- and C-TA33a predicted that Cys-9 and Cys-14 are connected by a disulfide bridge and form two beta-strands.

Amino Acid Sequence↗