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Biomedical subjects

M Véron

Publications and source records attributed to M Véron.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Adhesion to HeLa cells of Campylobacter jejuni and C. coli outer membrane components.

Adhesion of Campylobacter jejuni and C. coli to epithelial cells is thought to be a decisive step in enteritis. In this work, we tried to determine which bacterial components are responsible for this phenomenon. Outer membrane (OM) extracts were prepared from strains of C. jejuni (3 strains) and C. coli (2 strains). These strains had been isolated from stools of febrile patients with diarrhoea and were able to adhere to HeLa cells in culture. After incubation of bacterial OM extracts with HeLa cells in culture, bacterial adherent material was recovered, subjected to electrophoresis and immunoblotted. Bacterial adherent antigens were revealed by a rabbit antiserum raised against whole bacterial cells. Antigenic fractions, ranging from 26 to 30 kDa, were found to preferentially bind to HeLa cells (cell-binding fractions; CBF). These antigens were proteins and were distinct from flagellin and lipopolysaccharide. Bacteria incubated with a rabbit antiserum raised against homologous CBF, were unable to bind to HeLa cells. Moreover, the inhibitory effect decreased when the antiserum was diluted. Under the same conditions, a rabbit antiserum raised against a non-adherent OM fraction of 92 kDa did not prevent bacteria from binding to HeLa cells.

Antigens, Bacterial↗
PubMedDate not supplied

Phosphorylation of anti-HIV nucleoside analogs by nucleoside diphosphate kinase.

The reaction of NDP kinase with antiviral nucleoside triphosphates used in antiviral therapies was studied at the presteady state by fluorescence stopped-flow and compared with the steady-state parameters. The affinity of the analogs was determined by fluorescence titration of a mutated enzyme with an inserted Trp in the binding site. The lack of the 3' hydroxyl in analogs is shown to decrease the kcat more than the KD.

Anti-HIV Agents↗
PubMedDate not supplied

Activation of anti-reverse transcriptase nucleotide analogs by nucleoside diphosphate kinase: improvement by alpha-boranophosphate substitution.

Nucleoside activation by nucleoside diphosphate kinase and inhibition of HIV-1 reverse transcriptase were studied comparatively for a new class of nucleoside analogs with a borano (BH3-) or a thio (SH) group on the alpha-phosphate. Both the alpha-Rp-borano derivatives of AZT and d4T improved phosphorylation by NDP kinase, inhibition of reverse transcription as well as stability of alpha-borano nonophosphate derivatives in terminated viral DNA chain.

Anti-HIV Agents↗
PubMedDate not supplied

[Results of two methods for testing bacterial susceptibility to antibiotics: disk method and a new semi-automatic method in liquid medium (ABACR procedure) and comparison with the minimal inhibitory concentration (author's transl)].

A performance analysis was established between three methods for testing of bacterial susceptibility to sixteen antibiotics: agar dilution or minimal inhibitory concentration (MIC) method, agar diffusion or DISK method, and semi-automatic dilution in liquid medium or ABACR method. Precision of the three methods was determined using three reference strains in repetition experiments (9 repetitions for MIC, 60 repetitions for both DISK and ABAC). The results show that MIC method was the most precise, and that the precision of DISK and ABAC methods was not sifnificantly different. Fidelity of both DISK and ABAC methods was compared in taking as reference the MIC of 200 wild strains of Gram-negative bacteria. Omitting the data concerning trimethoprim-sulfamethozoaxol, the results were found concordant between DISK and MIC methods in 68.6 percent of the cases, between ABAC and MIC methods in 73.6 percent, and between ABAC and DISK methods in 68.9 percent. With regard to MIC, ABAC method gave results slightly better than those of DISK method, especially for five antibiotics: gentamicin, minocyclin, doxycylin, chloramphenicol and polymyxin B. So, the ABAC method looks very interesting for a semi-automatic routine method in testing bacterial susceptibility to antibiotics.

Anti-Bacterial Agents↗
PubMedDate not supplied

["In vitro" activity of a new cephalosporin (CGP-7174-E or cefsulodin) against "Pseudomonas aeruginosa" (author's transl)].

The minimal inhibitory concentration (MIC) of four betalactamins (carbenicillin, ticarcillin, piperacillin and (CGP-7174-E) against 109 clinical isolates of Pseudomonas aeruginosa was determined by an agar dilution method. CGP-7174-E was the most active (MIC 3.4 micrograms/ml), followed in descending order by piperacillin (MIC 4.9 micrograms/ml), ticarcillin (MIC 22 micrograms/ml) and carbenicillin (MIC 36 microgram/ml). High correlation was found between the MIC of these betalactamins (r greater than 0.60). In 12 strains where MIC for carbenicillin was greater than or equal to 1,024 microgram/ml, MIC for CGP-7174-E was less than or equal to 128 micrograms/ml and less than 16 micrograms/ml in four strains.

Carbenicillin↗
PubMedDate not supplied

[Evolution of fecal microflora in a "heteroxenic" infant maintained in a plastic isolator and trial on decontamination by antibiotherapy (author's transl)].

This work deals with the bacteriological study of an immunodeficient infant, delivered by aseptic cesarean section, and subsequently maintained in a plastic isolator. After a short period of germfree maintenance, several strains of bacteria were fortuitously introduced into the isolator, and became established in the infants' gastrointestinal tract. The qualitative and quantitative evolution of the fecal flora of this "heteroxenic" infant was followed for 170 days. Decontamination of the gastrointestinal tract was accomplished with a mixture of antibiotics, and the conditions of maintenance of sterility under antibiotic treatment were studied.

Age Factors↗
PubMedDate not supplied

[Kinetics of setting up of a human fecal flora in germ free mice and trial of decontamination of antibiotherapy (author's transl)].

We have tried in this study to reproduce in germfree mice a bacterial equilibrium observed previously in the gastrointestinal tract of child "L.N.", reared in a plastic isolator. Eight bacterial strains were studied. Seven had been fortuitously introduced: Acinetobacter lwoffi LN1, Staphylococcus epidermidis LN2, Clostridium perfringens LN3, Plectridium anatum LN4, Streptococcus bovis LN5, Enterobacter cloacae LN6, Corynebacterium sp LN7. The eighth strain was purposely administered to the child in order to take advantage of an antagonism between this strain and spontaneously acquired flora. This strain is Bacillus licheniformis FD1. The gnotoxenic mice proved to be a good experimental model because we found their bacterial equilibrium comparable to that observed in child L.N. In addition, we studied the decontamination procedures of the gastrointestinal tract of mice by observing both the antagonism of B. licheniformis with bacitracin, and the action of a suitable mixture of antibiotics. Conditions for the realization of this decontamination are discussed in this study.

Acinetobacter↗
PubMedDate not supplied

[Klebsiella pneumoniae infection in immunosuppressed mice treated with gentamicin (author's transl)].

Experiments have been established in order to study the antagonistic effect of cyclophosphamid treatment on the antibiotic activity of gentamicin in vivo. An immunodepressive state in mice (50 % reduction of neutrophil polymorphonuclear) was obtained with a 5 day treatment of cyclophosphamid, at the dose of 15 mg/kg. The mice were inoculated intraperitoneally with 10 LD50 of Klebsiella pneumoniae. Antibiotherapy was applied in 2 ways differing with the dose of gentamicin given twice a day by subcutaneous route (either 2.5 or 25 mg/kg) and with the time at which treatment was started (either at 1 or at 2 h after bacterial challenge). The gentamicin activity decreases in immunosuppressed mice when antibiotic is applied with a low dose (2.5 mg/kg), 1 h after infection challenge. This effect disappears when gentamicin is given with high doses (20 mg/kg) or when antibiotherapy is delayed (2 h after infection challenge). In this case, mortality is important and close to non immunodepressed mice.

Animals↗
PubMedDate not supplied

[Biochemical and serological characterization of "Bacillus sphaericus" strains, pathogenic or non-pathogenic for mosquitoes (author's transl)].

A biochemical and serological study of 35 Bacillus sphaericus strains including some pathogenic for mosquito larvae, is reported. A classification of these, and a differentiation of the pathogenic strains, cannot be made on the basis of the 78 phenotypic characters which have been determined by conventional methods. Numerical analysis of the results given by the auxanograms on 160 substrates, gives good results. An even more valuable approach is the flagellar agglutination technique, which clearly distinguishes the pathogenic from the non-pathogenic strains and furthermore can specifically differentiate strains among the pathogenic isolates.

Animals↗
PubMedDate not supplied

A complement-sensitive mutant of Pseudomonas aeruginosa.

The role of complement in the bactericidal activity of human serum against a mutant strain of Pseudomonas aeruginosa used as a model was demonstrated. The involvement of complement in the bacterial destruction of P. aeruginosa, and the contribution of the alternative and classical pathways of the complement system were directly evidenced by using sera from complement-deficient patients.

Animals↗
PubMedDate not supplied

[Ticarcillin activity in immunodepressed mice infected with "Pseudomonas aeruginosa" (author's transl)].

Ticarcillin (TCL) activity was studied in vivo in mice immunodepressed by either cyclophosphamide (CY) or methylprednisolone (Mpd). Each type of immunodepression was evaluated by polymorphonuclear enumeration and carbon black blood clearance. Mice were infected intraperitoneally with 3 LD50 of Pseudomonas aeruginosa and then 1,000 or 1,600 mg/kg of TCL was given by subcutaneous route. Mice were treated after 15 min and 3, 18, 24 and 36 h following infection. With 1,000 mg/kg of TCL, non-immunodepressed mice were cured. Mpd-treated mice were cured by 1,600 mg/kg of TCL, while CY-treated mice were not cured by the same dose of TCL.

Animals↗
PubMedDate not supplied

Susceptibility of mice to bacterial infections after chronic exposure to cadmium.

Susceptibility to bacterial infections after chronic exposure to cadmium was studied in mice. Cadmium chloride was injected intraperitoneally three times a week for 4 weeks. After this treatment, mice displayed splenomegalia, hyperplasia of the B-dependent areas of spleen. Virulence of bacteria considered as usually having extracellular sites of multiplication (Klebsiella pneumoniae, Pseudomonas aeruginosa), or intracellular (Listeria monocytogenes), was determined. Only L. monocytogenes showed an increased virulence in cadmium-treated mice.

Animals↗
PubMedDate not supplied

[Adherence of enteropathogenic "Escherichia coli" to mononuclear cells from human blood (author's transl)].

Two toxigenic strains of Escherichia coli possessing a colonization factor antigen (CFA) respectively CFA/I and CFA/II, were studied for adherence to mononuclear cells from human blood of 12 subjects. Significant differences were observed between these two strains in their ability to adhere, using as control strains their laboratory-passed derivatives which no longer possess CFA. Differences were observed in bacterial adhesion ability of mononuclear cells from different subjects but, in the whole, CFA+ bacteria were able to adhere to few cells from each subject only. These results are in opposition to the hypothesis that it is conceivable that histocompatibility antigens expressed on cells play a role in the attachment of bacteria as the first step in an infection.

Adhesiveness↗
PubMedDate not supplied

[Rapid determination of the minimal inhibitory concentration of an antibiotic by measuring bacterial ATP (author's transl)].

The minimal inhibitory concentrations (MIC) of gentamicin for ten strains of Enterobacteriaceae were determined by measuring the bacterial ATP (adenosine triphosphate). ATP was measured by chemiluminescence on 4-h growth cultures which included gentamicin. The MIC results obtained by this method were equivalent to those found with the technique of dilution in liquid medium.

Adenosine Triphosphate↗
PubMedDate not supplied

[The taxonomy of Salmonella].

A collection of 88 Salmonella reference strains including the so-called subgenus I (20 strains), subgenus II (21 strains), subgenus III (= Arizona, 21 strains), subgenus IV (20 strains) and 6 atypical strains (bongor group) was submitted to 90 carbon source utilization tests and 41 biochemical tests. A cluster analysis (Jaccard coefficient, clustering according to the variance) yielded 7 phenons; 35 strains from these 7 phenons were studied by DNA relatedness (S1 nuclease method with DE81 filters). Six hybridization groups, largely concordant with the phenon, were distinguished. Comparison of phenetic and genomic criteria allowed us to subdivide the genus Salmonella into 6 taxa corresponding to (1) subgenus I, subdivided phenotypically into an adapted group and a ubiquitous group, (2) subgenus II, (3) monophasic serovars of subgenus III, (4) diphasic serovars of subgenus III, (5) subgenus IV, and (6) bongor group. The taxonomic level of each of the 6 taxa is not that of a subgenus, but that of a subspecies.

DNA, Bacterial↗