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M Gueguen

Publications and source records attributed to M Gueguen.

At least 19 recordsLinked to original sources
PubMed2006

Identification of Geotrichum candidum at the species and strain level: proposal for a standardized protocol.

In this study, the M13 primer was used to distinguish Geotrichum candidum from the anamorphic and teleomorphic forms of other arthrospore-forming species (discriminatory power = 0.99). For intraspecific characterization, the GATA4 primer showed the highest level of discrimination for G. candidum among the 20 microsatellite primers tested. A molecular typing protocol (DNA concentration, hybridization temperature and type of PCR machine) was optimized through a series of intra- and interlaboratory trials. This protocol was validated using 75 strains of G. candidum, one strain of G. capitatum and one strain of G. fragrans, and exhibited a discrimination score of 0.87. This method could therefore be used in the agro-food industries to identify and to evaluate biodiversity and trace strains of G. candidum. The results show that the GATA4 primer might be used to differentiate strains according to their ecological niche.

Bacteriophage M13↗
PubMed2001

Usefulness of epifluorescence for quantitative analysis of lactobacilli in probiotic feed.

AIMS: Enumeration of total, active or viable probiotic micro-organisms from liquid or solid commercial feedstuffs was studied during processing and storage. METHODS AND RESULTS: After sample preparation, an epifluorescence microscopy technique and a plating method were investigated comparatively. It was shown that (i) on the day of manufacture, active or viable bacteria were in equivalent amounts and that viable numbers then decreased, depending on the different processing and storage factors enhancing ABNC production, (ii) the amount of total and active lactobacilli remained close and quite stable for months at a high level (>10(8) active fluorescent units). CONCLUSIONS: Processing and storage promoted ABNC cells in the products tested. Consequently, both techniques should be used to evaluate the viable-dead-active status of bacteria for which functional properties are claimed. SIGNIFICANCE AND IMPACT OF THE STUDY: Enumeration of the whole probiotic bacterial population should be take into account for guidelines and labelling since non-viable bacteria could have a probiotic effect.

Bacteriological Techniques↗
PubMed2000

Flavour sulphides are produced from methionine by two different pathways by Geotrichum candidum.

We have investigated the capacities of Geotrichum candidum strains to produce sulphides from methionine. This attribute is very important in cheese technology because of the flavouring potential of sulphur compounds. A spectrophotometric procedure using 5,5'-dithiobis(2-nitrobenzoic acid) to determine sulphides was tested on a collection of G. candidum strains, and confirmed by gas chromatography-mass spectrometry. The strains were distinguished on the basis of their ability to produce methanethiol. Gas chromatography-mass spectrometry also made it possible to identify other sulphides, such as dimethyl disulphide, dimethyl trisulphide and dimethyl sulphide. Using sonicated cells, the specific production of these four sulphides was studied in presence of L-[S-methyl-2H]methionine. Both methanethiol and dimethyl sulphide were produced from methionine, but two different pathways were used by G. candidum.

Cheese↗
PubMed1999

Correlation between polymerase chain reaction analysis of the histidine biosynthesis operon, randomly amplified polymorphic DNA analysis and phenotypic characterization of dairy Lactococcus isolates.

A collection of 32 lactococcal strains isolated from raw milk in the Camembert RDO (registered designation of origin) area were phenotypically and genotypically characterized. As expected for environmental isolates, all strains had a Lactococcus lactis subsp. lactis phenotype. The strains were then genotypically identified by the randomly amplified polymorphic DNA (RAPD) technique, using reference strains of lactococci. Two major clusters were identified containing the two subspecies lactis and cremoris. The subspecies lactis cluster could be divided into five subgroups whereas there was a high coefficient of similarity between all strains in the subspecies cremoris cluster. This RAPD classification was then compared with that of a traditional PCR assay using L. lactis species-specific primers corresponding to part of the histidine biosynthesis operon. The two subspecies were differentiated by the size of the fragment amplified (about 200 bp longer for subspecies cremoris). Unlike preliminary phenotypic assignments, the results of PCR experiments corroborated the genotypic identification of the lactococcal strains by RAPD allowing the technique to be reconsidered on the basis of its taxonomic efficiency.

Animals↗
PubMed1999

Genetic diversity among dairy lactococcal strains investigated by polymerase chain reaction with three arbitrary primers.

Randomly amplified polymorphic DNA (RAPD) has been used for the rapid typing of Lactococcus lactis strains isolated from raw milk from the Camembert region of Normandy. It is thought that the diversity and perhaps the area strain specificity due to climatic and geographical factors of such wild-type lactococcal strains could contribute to the flavour differences and specific features detected for the same product in different areas. The patterns from 58 isolates were analysed by UPGMA dendrograms. At a similarity level of 50%, four RAPD clusters were distinguished. Clusters 1 and 2 contained strains of subspecies lactis and cluster 3 contained strains related to the C2 strain which is genetically cremoris but phenotypically lactis. The type strain of cremoris subspecies was significantly differentiated from these strains with primers P2 and P3. Thus, there was a real genetic diversity in pattern, making it possible to detect potential typical RAPD fragments.

Animals↗
PubMed1998

An ecological study of lactococci isolated from raw milk in the camembert cheese registered designation of origin area.

The genetic diversity of lactococci isolated from raw milk in the Camembert cheese Registered Designation of Origin area was studied. Two seasonal samples (winter and summer) of raw milk were obtained from six farms in two areas (Bessin and Bocage Falaisien) of Normandy. All of the strains analyzed had a Lactococcus lactis subsp. lactis phenotype, whereas the randomly amplified polymorphic DNA (RAPD) technique genotypically identified the strains as members of L. lactis subsp. lactis or L. lactis subsp. cremoris. The genotypes were confirmed by performing standard PCR with primers corresponding to a region of the histidine biosynthesis operon. The geographic distribution of each subspecies of L. lactis was determined; 80% of the Bocage Falaisien strains were members of L. lactis subsp. lactis, and 30.5% of the Bessin strains were members of L. lactis subsp. lactis. A dendrogram was produced from a computer analysis of the RAPD profiles in order to evaluate the diversity of the lactococci below the subspecies level. The coefficient of similarity for 117 of the 139 strains identified as members of L. lactis subsp. cremoris was as high as 66%. The L. lactis subsp. lactis strains were more heterogeneous and formed 10 separate clusters (the level of similarity among the clusters was 18%). Reference strains of L. lactis subsp. lactis fell into 2 of these 10 clusters, demonstrating that lactococcal isolates are clearly different. As determined by the RAPD profiles, some L. lactis subsp. lactis strains were specific to the farms from which they originated and were recovered throughout the year (in both summer and winter). Therefore, the typicality of L. lactis subsp. lactis strains was linked to the farm of origin rather than the area. These findings emphasize the significance of designation of origin and the specificity of "Camembert de Normandie" cheese.

Animals↗
PubMed1998

Purification and characterization of anti-Listeria compounds produced by Geotrichum candidum.

Geotrichum candidum can produce and excrete compounds that inhibit Listeria monocytogenes. These were purified by ultrafiltration, centrifugal partition chromatography, thin-layer chromatography, gel filtration, and high-pressure liquid chromatography, and analyzed by liquid chromatography-mass spectrometry, infrared spectrometry, nuclear magnetic resonance spectrometry, and optical rotation. Two inhibitors were identified: D-3-phenyllactic acid and D-3-indollactic acid.

Anti-Bacterial Agents↗
PubMed1997

Monitoring the microbiology of high quality milk by monthly sampling over 2 years.

The concentrations of seven types of microorganism in the milk produced by farms using high quality milking procedures were monitored monthly. The most commonly encountered bacterium was Pseudomonas, whose concentration varied greatly between samples, but lactococci, lactobacilli and yeasts were also present at more stable concentrations. Staphylococcus aureus and beta-glucuronidase-positive Escherichia coli were occasionally detected. Listeria monocytogenes was found in the samples from only one farm, while Yersinia enterocolitica was never detected. There were seasonal variations in the concentrations of lactobacilli and yeasts over the 2 years monitored. The changes in certain bacteria (Lactococcus, Lactobacillus) on any given farm were very similar from one year to the next. The microbiological characteristics of the milk from the farms examined seemed to be fairly constant. The profiles of some bacteria used for cheesemaking were relatively stable over time. It thus seems that the milk provided by different producers could be typed.

Analysis of Variance↗
PubMed1997

High prevalence of antibodies to Mycoplasma penetrans in human immunodeficiency virus-seronegative and -seropositive populations in Brazzaville, Congo.

In industrialized countries, the prevalence of antibodies to Mycoplasma penetrans is higher among human immunodeficiency virus (HIV)-seropositive homosexuals than other HIV-seropositive and HIV-seronegative groups. In an African heterosexual population, we found a higher prevalence of M. penetrans antibodies in HIV-seronegative blood donors (15.5%) than in France (0.9%) or the United States (0.3%) and a prevalence of 13.4% in HIV-seropositive individuals. HIV-seropositive individuals with less than 5% CD4 cells had a higher prevalence of M. penetrans antibodies than individuals with 5% or more CD4 cells (25.0 versus 8.5%).

Adult↗
PubMed1991

A mammalian tryptophanyl-tRNA synthetase shows little homology to prokaryotic synthetases but near identity with mammalian peptide chain release factor.

Determination of the amino acid sequence of beef pancreas tryptophanyl-tRNA synthetase was undertaken through both cDNA and direct peptide sequencing. A full-length cDNA clone containing a 475 amino acid open reading frame was obtained. The molecular mass of the corresponding peptide chain, 53,728 Da, was in agreement with that of beef tryptophanyl-tRNA synthetase, as determined by physicochemical methods (54 kDa). Expression of this clone in Escherichia coli led to tryptophanyl-tRNA synthetase activity in cell extracts. The open reading frame included two sequences analogous to the consensus sequences, HIGH and KMSKS, found in class I aminoacyl-tRNA synthetases. The homology with prokaryotic and yeast mitochondrial tryptophanyl-tRNA synthetases was low and was limited to the regions of the consensus sequences. However, a 90% homology was observed with the recently described rabbit peptide chain release factor (eRF) [Lee et al. (1990) Proc. Natl. Acad. Sci. 87, 3508-3512]. Such a strong homology may reveal a new group of genes deriving from a common ancestor, the products of which could be involved in tRNA aminoacylation (tryptophanyl-tRNA synthetase) or translation termination (eRF).

Amino Acid Sequence↗
PubMed1991

Cytochrome P450IID subfamily in non-human primates. Catalytical and immunological characterization.

Interindividual variations of debrisoquine metabolism was recently identified in non-human primates tested in vivo. The catalytical and immunological characterization of cytochrome P450IID subfamily was undertaken in hepatic microsomes from extensive metabolizer primates. The NADPH/O2 mediated metabolism of debrisoquine, dextromethorphan and bufuralol was similar to the kinetics reported in humans. The CuOOH mediated metabolism of bufuralol suggested that at least two enzymes are responsible for bufuralol 1'-hydroxylation. Eleven compounds were tested for their capacity to modify P450IID function in vitro. Eight competitive inhibitors of P450IID6 in man were all and exclusively competitive inhibitor of P450IID subfamily in non-human primates. Quinidine, which is the strongest competitive inhibitor in man, exhibited the higher inhibitory potency in monkey (Ki = 0.75 microM). Anti-LKM antibody against P450IID subfamily cross-reacted with two proteins of 49 and 47 kDa, and sera containing anti-LKM antibody against these two proteins inhibited dextrorphan formation in vitro. These data provide evidence for catalytical and immunological similarities between human and monkey microsomes and indicate that the primate system could be a model for enzymatic studies of P450IID.

Animals↗
PubMed1991

Hepatitis B virus infection markers in genetic haemochromatosis. A study of 272 patients.

Serum hepatitis B virus (HBV) infection markers were studied in 272 patients with homozygous genetic haemochromatosis complicated (n = 33) or not (n = 239) with primary liver cancer (PLC). Controls consisted of 255 029 healthy blood donors from whom age- and sex-matched control groups were extracted for statistical evaluation using the Fisher exact test. In blood donors, HBsAg was positive in 0.075% of males and 0.04% of females. This population was not screened for anti-Hbs. Anti-Hbc alone (without HBsAg) was present in 3.7% of men and 1.8% of women. In patients with genetic haemochromatosis without liver cancer (183 males, 45.6 +/- 11.3 yrs and 56 women, 48 +/- 12.4 yrs), HBsAg was found in 1.1% of men and in none of the women. Anti-HBs was present in 7.3% of males and 1.8% of females. Anti-HBc alone was found in 13% of males (p less than 0.005 vs. controls) and 2.1% of females. From male patients with primary liver cancer complicating genetic haemochromatosis (32 males, 61.7 +/- 6.8 yrs and one female), 6.2% were HBsAg positive, 3.4% were anti-HBs positive and 16.6% anti-HBc positive (p = 0.05 vs. controls). No serum HBV marker was found in the woman. In conclusion, the prevalence of HBV infection markers--especially anti-HBc--is significantly increased in patients with genetic haemochromatosis complicated or not with primary liver cancer.

Adult↗
PubMed1991

Identification of the main epitope on human cytochrome P450 IID6 recognized by anti-liver kidney microsome antibody.

Antibodies present in the sera of a group of children with autoimmune hepatitis react with human cytochrome P450 IID6. cDNA constructions of various fragments of human P450 IID6 were made and expressed and the resulting peptides were tested in immunoblot with patients' sera. These allowed identification of at least two antigenic sites on the P450 molecule. The main one, recognized by all sera tested, is located between amino acids 239 and 271. Synthesis of three peptides covering this area of the molecule allowed identification of a sequence of three amino acids (tyrosine-tryptophane-asparagine) located at position 261-263 that constitutes the essential part of the epitope. A protein sequence data-base search revealed homologies between this region of human P450 and proteins from Salmonella typhimurium, from human T lymphotropic virus types 1 and 2 and Herpes simplex virus type 1.

Amino Acid Sequence↗
PubMed1990

[Prevalence and epidemiologic features of subjects found to be infected with HIV when donating blood. CTS of the "Retrovirus" Study Group of the Société Nationale de Transfusion Sanguine].

HIV seroprevalence decreased from 0.62% in 1985 to 0.11% in the first 1990 semester. However, the number of regular blood donors screened as seropositive remains constant since 1988: 48 in 1988, 49 in 1989 and 25 in the first 6 months of 1990. From these data, from reports on recipients and due to the exclusion of 30% of such donors by anti-HBc screening, the residual risk to transmit HIV by blood transfusion was estimated to 17 blood donations per year in France. No significant change was observed throughout these years either in sex ratio or in the repartition into age groups. The number of HIV-infected subjects through the heterosexual route has not increased. The number of homosexuals and of IVDA has dramatically decreased since 1985, homosexuals still representing the major at-risk group.

Adult↗
PubMed1989

Anti-liver-kidney microsome antibody type 1 recognizes human cytochrome P450 db1.

Anti-liver-kidney microsome antibody type 1 (LKM1), present in the sera of a group of children with autoimmune hepatitis, was recently shown to recognize a 50 kDa protein identified as rat liver cytochromes P450 db1 and db2. High homology between these two members of the rat P450 IID subfamily and human P450 db1 suggested that anti-LKM1 antibody is directed against this human protein. To test this hypothesis, a human liver cDNA expression library in phage lambda GT-11 was screened using rat P450 db1 cDNA as a probe. Two human cDNA clones were found to be identical to human P450 db1 by restriction mapping. Immunoblot analysis using as antigen, the purified fusion protein from one of the human cDNA clones showed that only anti-LKM1 with anti-50 kDa reactivity recognized the fusion protein. This fusion protein was further used to develop an ELISA test that was shown to be specific for sera of children with this disease. These results: 1) identify the human liver antigen recognized by anti-LKM1 auto-antibodies as cytochrome P450 db1, 2) allow to speculate that mutation on the human P450 db1 gene could alter its expression in the hepatocyte and make it auto-antigenic, 3) provide a simple and specific diagnostic test for this disease.

Autoantibodies↗
PubMed1989

HIV 2 infection among blood donors and other subjects in France. The "Retrovirus" Study Group of the French Society of Blood Transfusion.

During a 3 year period, from August 1985 to August 1988, 18 HIV 2-infected blood donors were detected in France as a result of systematic HIV 1 screening. These sera were characterized as HIV 2 by specific Western blot and synthetic peptides. Within the same period, 40 other HIV 2 infected subjects were identified by our study group, independently of blood donations. Thirty of these 58 subjects living in France originate from West Africa (8 blood donors), 3 (I blood donor) are Portuguese men who had lived in West Africa and 25 (9 blood donors) are of French origin; among these, 16 have had a known close contact with West Africa. When HIV 2-infected subjects were asymptomatic, cross reactivity between antibodies to HIV 2 and HIV 1 proteins was generally observed with the two-step ELISA assays using total HIV 1 proteins; it was poor with the competitive assays and variable with the assays using recombinant proteins. When the subjects had signs of immunodeficiency, cross reactivity decreased. The data confirm that HIV 2 is not widespread in France and that most of HIV 2-infected but asymptomatic subjects are recognized by several HIV 1 ELISA assays. Accordingly, systematic screening for HIV 2 with an additional test cannot be recommended at the present time, but a combined HIV 1 and HIV 2 test will be useful when available.

Acquired Immunodeficiency Syndrome↗