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Biomedical subjects

R Ducluzeau

Publications and source records attributed to R Ducluzeau.

At least 19 recordsLinked to original sources
PubMed1992

Colonization of the digestive tract of germ-free mice by genetically engineered strains of Lactococcus lactis: study of recombinant DNA stability.

The ability of genetically engineered Lactococcus lactis strains to become established in the digestive tract (DT) of germ-free mice was examined together with the stability of their genetic markers. Seven L. lactis strains were genetically modified by insertion of genetic markers on different replicons: chloramphenicol resistance gene cat was carried by self-transmissible plasmid pIL205, a derivative of plasmid pIP501; erythromycin resistance gene erm, originating from pAM beta 1, was inserted into non-transmissible plasmids pIL252 and pIL253 of low and high copy number respectively; erm gene from plasmid pMS1.5B was inserted into the chromosome. All strains carried a common wild-type plasmid pIL9 involved in lactose fermentation. It was observed that the DT of mice was rapidly and efficiently colonized with either the inoculated parental strain or with its derivatives or with both of them, but plasmid-free derivatives were always at dominant levels. Both plasmids pIL9 and pIL205 were lost, but the parental strains and the plasmid-lacking derivatives were at codominant levels, indicating that there is an equilibrium between plasmid loss and plasmid transfer in the DT. Strains that carried non-transmissible and low copy number plasmid pIL252 were rapidly eliminated from the DT, which in turn was colonized with the respective pIL252-less derivatives; this is probably due to the high segregational instability of pIL252.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Antagonism exerted by an association of a Bacteroides thetaiotaomicron strain and a Fusobacterium necrogenes strain against Clostridium perfringens in gnotobiotic mice and in fecal suspensions incubated in vitro.

Antagonism between an association of Bacteroides thetaiotaomicron and Fusobacterium necrogenes strains and two strains of Clostridium perfringens was evidenced both in vivo in gnotobiotic mice and ex vivo in fecal suspensions incubated for 22 h at 37 degrees C. Several features of this antagonism were similar in and ex vivo. (i) An obligate and continuous synergy between B. thetaiotaomicron and F. necrogenes was required; (ii) the two C. perfringens strains did not respond to the same extent to this antagonism; and (iii) expression of the antagonism was host and diet dependent. Neither diffusible nor soluble inhibitory substances were detectable in feces of gnotobiotic mice, nor could depletion of nutrients be identified as causing antagonism in both in and ex vivo experiments. Our findings support the hypothesis that a reversible bacteriostasis induced by the inhibitory strains acting together continuously, and hindering the target strain from utilizing available nutrients, was responsible for this antagonism.

Animals↗
PubMed1987

Antagonistic effect exerted by three strictly anaerobic strains against various strains of Clostridium perfringens in gnotobiotic rodent intestines.

Our purpose was to study bacterial antagonism between a limited number of strictly anaerobic strains and Clostridium perfringens in the intestinal tract of gnotobiotic rodents. Gnotobiotic mice harboring a Bacteroides thetaiotaomicron, a Fusobacterium necrogenes, and a Clostridium sp. strain were protected against pathogenic B, C, and D C. perfringens serotypes. A drastic antagonistic effect of this three-strain association was also observed against a nonpathogenic C. perfringens serotype A (CpA). It was less efficient in gnotobiotic rats than in mice and less efficient in gnotobiotic mice fed an autoclaved diet than in mice fed the same diet sterilized by irradiation. No diffusible inhibitory substances against CpA were detected in feces of gnotobiotic mice harboring the three antagonistic strains, and no nutrient depletion was demonstrated in filtrates prepared from 10-fold diluted feces of these mice. In vitro mixed cultures of the three antagonistic strains failed to inhibit growth of CpA, whereas CpA did not multiply in a 10-fold diluted feces from gnotobiotic mice. A reverse correlation between the initial number of antagonistic strains and the division number of CpA was determined using serially diluted fecal suspensions. Thus, large numbers of viable cells of both antagonistic strains were required to inhibit the target strain in fecal suspensions as was also found in gnotobiotic mice intestines. However, no diffusible inhibitory substance was detectable nor could depletion of growth factors be identified as causing antagonism. Whatever factors that may be responsible for antagonism were found to be influenced by the host and its diet.

Animals↗
PubMed1986

Prevention of Clostridium difficile induced mortality in gnotobiotic mice by Saccharomyces boulardii.

Oral preventive treatment of gnotobiotic mice by Saccharomyces boulardii significantly decreased mortality following Clostridium difficile infection. A single S. boulardii ingestion protected 16% of mice, whereas 56% were protected when S. boulardii was given continuously in the drinking water. No direct antagonistic effect of the yeast on C. difficile numbers was detected, whereas a modulation of fecal cytotoxin production was demonstrated.

Animals↗
PubMed1986

[Kinetics of establishment of digestive microflora in the human newborn infant as a function of the kind of milk].

The digestive tract of human infants, sterile at birth, is colonized by some bacterial genera within less than 48 h. Among the factors involved in the implantation of a given bacterial genus, the type of milk fed plays a major role. We studied the development of fecal flora in 1 to 8-day old babies, either breast-fed or bottle-fed with humanized milk. In breast-fed infants the microflora reached an equilibrium towards the age of 5 days and then hardly varied until the change of feeding. Escherichia coli and Streptococcus were established first and Bifidobacterium later. At the age of 5 days, the strictly anaerobic flora was exclusively composed of Bifidobacterium in 85% of cases. The development of other strictly anaerobic bacteria was repressed, particularly that of Bacteroides. In infants receiving humanized milk, Escherichia coli (or sometimes other enterobacteria) also appeared very early in the digestive tract. However, the strictly anaerobic flora was either absent (40% of cases) or composed of one or more genera (e.g. Bacteroides, Bifidobacterium, Plectridium). These findings in human infants show that it is mainly the establishment of the strictly anaerobic flora which is affected by the type of milk fed.

Anaerobiosis↗
PubMed1985

Resistance of gnotobiotic large white and Chinese piglets to in vivo attachment of a K88ab enterotoxigenic Escherichia coli strain.

In vivo adhesion of a K88ab-positive enterotoxigenic Escherichia coli (ETEC) strain to the small intestinal wall of gnotobiotic, colostrum-deprived Chinese and Large White piglets was investigated. A non-enterotoxigenic, attachment factor-deprived E. coli strain, inoculated in association with the K88ab ETEC strain, was used as a marker to determine the content residues on the intestinal walls of gnotobiotic piglets. Both strains were selectively numerated in the luminal contents and on the washed wall from three segments of the small intestine. In vivo attachment was assessed by the ratio between the number of K88ab ETEC adherent to the wall and the number of both the E. coli strains which came from the luminal content residues and were not completely removed by washing. This ratio was first calculated in one group of 8 Large White piglets associated with the marker strain and with a K88ab antigen-deprived E. coli which derived from the parental K88ab ETEC strain. Thus, the range of the ratio was determined in those piglets where no attachment was expected. A comparison between the latter values of the ratio and the values obtained from 15 Large White and 10 Chinese piglets inoculated with the marker strain and the K88ab ETEC strain allowed us to classify the Large White piglets into adhesive (8 piglets) and non-adhesive (7 piglets) phenotypes and to show that the 10 Chinese piglets belonged to the non-adhesive phenotype.

Animals↗
PubMed1985

Inhibitory effect of a copper-dipeptide complex on the establishment of a Clostridium perenne strain in the intestinal tract of gnotobiotic mice.

A semisynthetic diet fed to axenic mice was found to prevent the establishment of a Clostridium perenne strain in their intestinal tract. This inhibitory effect did not occur when axenic mice were preinoculated with a strain of Clostridium difficile. The inhibitory effect was related to the presence in the intestinal contents of axenic mice of both dietary copper and a dipeptide, aspartic-epsilon-lysine. When C. difficile was inoculated into axenic mice, the dipeptide disappeared from the digesta, and C. perenne became established even in the presence of high concentrations of copper.

Animals↗
PubMed1983

Intraspecific interactions between Escherichia coli strains in human newborns and in gnotobiotic mice and piglets.

A plasmid-free human Escherichia coli strain EMO, was inoculated to human newborns within two hours of life. It became established in the feces at a high population level. Ampicillin and tetracycline resistant E. coli strains disappeared or decreased to subdominant level in the inoculated newborns whereas they remained at a high level in the noninoculated newborns. Strain EMO was also shown to exert a barrier effect against a porcine plasmid-bearing enterotoxigenic Ent+ K88- E. coli strain in gnotobiotic mice. Axenic piglets monoassociated with Ent+ K88- E. coli strain died within 6 days. Axenic piglets diassociated with both EMO and the Ent+ E. coli survived longer, though no significant difference was observed between the population level of the Ent+ E. coli in the mono- and diassociated piglet feces. These results suggest that a prior inoculation with a non-pathogenic E. coli strain may improve the spontaneous ecological protection of piglets against Ent+ E. coli strains.

Animals↗
PubMed1983

[Acute ajmaline poisoning. Study of 7 cases].

Seven cases of acute ajmaline overdose admitted over a 3 year period to a polyvalent intensive care unit are reported. The severity of this condition is related to the membrane stabilising and depolarising effects of ajmaline on the myocardium. The dose ingested varied from 10 to 40 mg/kg. The delay between ingestion and hospital admission ranged from 3 to 6 1/2 hours. The first cardiac disturbances can appear one hour after ingestion. Three cardiac arrests and one hypovolemic shock occurred. Three atrioventricular blocks, six intraventricular blocks, three ventricular tachycardias, and six prolongations of the QT interval were observed. Serum ajmaline levels varied from 0,8 to 6 mg/l. Symptomatic therapy was mainly based on sodium, temporary cardiac pacing, external DC shock, sympathomimetics and external cardiac massage with assisted ventilation. Cardiac bypass should be a part of the therapeutic arsenal. Elimination of the drug is assisted by a complete digestive evacuation. Renal or extrarenal dialysis is not indicated. One of the seven patients died. Prophylaxis is based on the non-prescription of ajmaline for benign cardiac disturbances.

Adolescent↗
PubMed1980

[Interest in gnotoxenic systems for the study of host-microbial flora of the digestive tract].

It is necessary to use experimental models in all studies of interactions between a host, its digestive tract microbial flora and the environment because these interactions are complex. The gnotoxenic animal, reared in an isolator as the axenic animal and harbouring a known microbial flora, constitutes either an analytic or mimetic experimental model. The gnotoxenic animal may be considered as an analytic model when used to determine which biotic or abiotic environmental factor of the host-animal plays a role in the intestinal ecosystem. The potential metabolic or immunologic role of a given bacterial strain in the intestinal ecosystem may be determined when the axenic animal is associated with this strain. The variation of the expression of the potential role of this strain in relation to the environment can be ascertained by diversifying the diet of the host or by introducing other bacterial strains into the intestinal ecosystem. The role of an association of strains in host physiology and host protection against potentially pathogenic target strains can also be studied using this analytic model. An analytic model is created by associating either isolated strains of the holoxenic or heated or diluted suspensions of holoxenic digestive tract flora. Axenic mice associated with these simplified flora are called meroxenic. The gnotoxenic animal is considered to be a mimetic model when it harbours a microbial flora isolated from an animal of a different species. The advantage of the mimetic model is that it provides an easy-to-use biological tool, i.e. gnotoxenic mice, to first determine the potential role of these microbial strains. The validity of the mimetic model is then tested by comparing gnotoxenic mice and gnotoxenic piglets or chickens. When all the gnotoxenic animals are given the same diet, this comparison permits an estimation of the animal-host role in the expression of the potential activities of microbial strains. The mimetic model, composed of gnotoxenic animals harbouring microbial strains of human origin, is the only experimental model which can be used to study the role of microorganisms in the intestinal ecosystem of man.

Animals↗