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Biomedical subjects

D E Corpet

Publications and source records attributed to D E Corpet.

47 records · Page 3Linked to original sources
PubMed1987

Antibiotic residues and R-plasmid selection: are in vitro methods good models?

Three clones of E. coli, one of which was harbouring a tetracycline resistance plasmid were inoculated together into the stomach of axenic mice. Without antibiotic selective pressure, the R-Plasmid bearing strain became dominant in the faeces of mice, while the R-plasmid free strain was eliminated. When the R-plasmid bearing strain was given to mice 4 days after the inoculation with the R-plasmid free strain, it was repressed and remained at the stable level of 10(4.5) organisms per g of faeces. But a rapid spread of the R-plasmid was observed, tetracycline resistant bacteria become dominant within one day, and replace the tetracycline sensitive E. coli. The tetracycline resistance plasmid did not disadvantage the mediating strain in the gut, even in the absence of antibiotic pressure. In contrast Lebek and Egger (1983), studying the same strains in vitro, found that in a chemostat the plasmid bearing strain was overgrown by the plasmid free strain. These results strongly suggest that in vitro interactions between E. coli strains cannot be directly extrapolated to in vivo conditions. For the determination of the no-effect level of antibiotic residue on the selection of R-factor in the gut, studies should be made in vivo.

Animals↗
PubMed1987

Antibiotic residues and drug resistance in human intestinal flora.

The effect of residual levels of ampicillin on the drug resistance of fecal flora was studied in human volunteers given 1.5 mg of ampicillin orally per day for 21 days. This treatment failed to have any significant reproducible effect on the number of resistant Escherichia coli in their feces. The effect of continuous administration of small doses of ampicillin, chlortetracycline, or streptomycin in the drinking water was studied in gnotobiotic mice inoculated with a human fecal flora. In this animal model, which is free of many interfering factors, an increase in the fecal concentration of resistant E. coli was observed when the mice were given 0.5 microgram of ampicillin or chlortetracycline per ml of water. This model is therefore a sensitive system for testing the effect of antimicrobial drugs on the resistance characteristics of the intestinal flora.

Administration, Oral↗
PubMed1986

Ecological factors influencing the transfer of plasmids in vitro and in vivo.

Plasmid transfer in the gut depends on the concentrations of recipient and donor bacteria and on their fertility. The main determining factors for the former are flow rate, concentration of limiting substrate, growth rates, adhesion, contamination and segregation and of the latter plasmid content, growth phase, and ecological conditions. These factors have to be measured with experimental models, and included in mathematical models, to estimate their relative incidence.

Bacteria↗
PubMed1983

Comparative metabolism of chloramphenicol in germfree and conventional rats.

The action of gut microflora on the metabolism of chloramphenicol (CP) was studied in germfree (GF) and conventional (CV) rats after administration of single oral doses of tritiated CP. There were similarities in the metabolic pathways of CP in the GF and CV animals, i.e., rapid absorption, hepatic glucuroconjugation, and biliary excretion of the CP conjugate. CP, CP-oxamic acid, CP-alcohol, and CP-base were present in similar proportions in the urine of both GF and CV rats. Differences observed included the slow elimination of total radioactivity and a reduced proportion of the urinary excretion versus the fecal excretion in the GF Reduction products which were present in much greater quantities in the urine and feces of CV rats are compatible with the generally described hydrolysis of the CP-glucuronide, followed by a nitroreduction of the CP by the gut microflora and the reabsorption of a part of the products formed. In GF rats, CP-glucuronide was the major fecal metabolite, a portion of it having been reabsorbed and excreted in the urine. Although in lesser amounts, reduction products were still present as urinary metabolites in GF rats. Such a reduction in the tissues might produce active intermediate that could be related to CP toxicity.

Animals↗
PubMedDate not supplied

The effect of bambermycin, carbadox, chlortetracycline and olaquindox on antibiotic resistance in intestinal coliforms: a new animal model.

Groups of germ-free mice kept in isolators and associated with faecal microflora from piglets were continuously given either water or a solution of one of the following: chlortetracycline (20 micrograms/ml), carbadox (50 micrograms/ml), olaquindox (50 micrograms/ml), bambermycin (flavomycin) (5 micrograms/ml) or mixtures of these drugs. The proportions of lactose-fermenting bacteria in their faeces which were resistant to chlortetracycline, carbadox or olaquindox were measured by a comparative plate-counting procedure. Compared to occurrence in control mice, the occurrence of antimicrobial drug-resistant bacteria was higher in mice receiving chlortetracycline (P less than 0.001) and lower in mice receiving bambermycins (P less than 0.005). In contrast, olaquindox and carbadox did not change the proportion of resistant coliforms in mice faeces. A control experiment was conducted with five groups of germ-free mice given the same flora and kept without drugs in separate isolators. No difference in the occurrence of resistant coliforms could be found between these groups. The germ-free mouse associated with faecal microflora from a conventional animal seems to be a suitable model for determining in vivo the effect of low doses of antimicrobial drugs on drug resistance in lactose-fermenting enteric flora.

Animal Feed↗
PubMedDate not supplied

Bioautographic method for evaluation of glycopeptide actaplanin in milk.

A bioautographic method is described that allows the identification and semiquantitation of residues of the glycopeptide antibiotic actaplanin in cow's milk at 0.01 ppm. The milk sample is precipitated with acetonitrile and the resultant pellet is extracted by a buffer. This extract is defatted, then chromatographed on an Amberlite resin column. Actaplanin is eluted with methanol-HCl. Purified extract is then chromatographed on a cellulose thin layer, developed in a methanol-chloroform-ammonium hydroxide mixture. This thin layer chromatography increased the sensitivity of the determination by concentrating the actaplanin components in a single spot. The antibiotic was then detected by bioautography, using Bacillus subtilis as a test organism. Parameters influencing the diffusion of the antibiotic (namely, the nature and concentration of the agar-agar), and the sensitivity of the test strain (namely, the nutritional value of the medium, and the addition of a synergistic inhibitor) have been optimized.

Animals↗
PubMedDate not supplied

Simple and ion-pair high performance liquid chromatography as an improved analytical tool for chloramphenicol metabolic profiling.

Simple and ion-pair reverse phase high performance chromatographic separations combined with selective extraction were developed in order to achieve a qualitative and quantitative analysis of [3H]chloramphenicol (CP) metabolites in rat urine. Complete separation followed by unequivocal identification of all the metabolites was obtained, especially of the toxicologically significant CP-arylamine. Metabolic profiles were established from human and goat urine which confirmed data already available, but was used to identify new acidic metabolites in the latter species. This methodology appears to be a useful research tool in comparative metabolic studies.

Animals↗