Robert Ducluzeau

Implantation of bacteria from the digestive tract of man and various animals into gnotobiotic mice.

Fourteen microbial strains isolated from conventional rats were inoculated into axenic rats and mice receiving identical diets. The populations of these organisms which became established in the feces of gnotobiotic adult recipient rats and mice were quite similar. The only major difference was that one strain, belonging to the genus Clostridium, disappeared from the feces of gnotobiotic mice, whereas this strain became established in gnotobiotic rats. Most of the strictly anaerobic strains were absent or present only in small numbers before weaning in young rats and mice. A clear-cut barrier effect against Salmonella typhimurium was found in adult gnotobiotic mice colonized with a complex flora derived from a conventional chicken. The microflora established in these recipient mice exerted the same barrier effect when further transferred into axenic chickens. Inoculation of feces from a human donor into adult gnotobiotic recipient mice produced colonization by several strains from the donor, whereas other strains, belonging to the genera Bifidobacterium, Lactobacillus, and Clostridium were present in the donor, but did not persist in recipient mice. In these mice, nonetheless, the colonizing human fecal flora exerted an effective barrier against a toxigenic strain of Clostridium difficile. This barrier effect spontaneously disappeared several weeks later. Administration of clindamycin to the recipient mice led to large variations in the number of viable cells of C. difficile.

Inhibition of Clostridium perfringens by an Antibiotic Substance Produced by Bacillus licheniformis in the Digestive Tract of Gnotobiotic Mice: Effect on Other Bacteria from the Digestive Tract

A strain of Bacillus licheniformis, established in the digestive tract of gnotobiotic mice, inhibited the subsequent establishment of a Clostridium perfringens strain ingested by the animals. This inhibitory effect depended on the in vivo production by B. licheniformis of an antibiotic substance having a number of the characteristics of bacitracin. If C. perfringens was the first to become established in the digestive tract of the gnotobiotic mice, B. licheniformis also became established but did not produce any antibiotic. Mutants of C. perfringens resistant to the antibiotic substance were not observed when the antibiotic was produced in situ by B. licheniformis, but were rapidly selected when the Bacillus culture filtrate or bacitracin was administered per os. B. licheniformis was also capable of eliminating from the digestive tract 5 of the 13 additional bacterial strains tested.

Production of an Antibiotic Substance by Bacillus licheniformis Within the Digestive Tract of Gnotobiotic Mice

In monoxenic mice, vegetative cells and spores of Bacillus licheniformis were enumerated and in vivo antibiotic production was measured at various levels of the digestive tract and in the feces. The apparent independence of vegetative cell and spore populations in the cecum and feces, as well as the marked fluctuations of these two populations in the stomach and small intestine, suggested that sporulation of B. licheniformis and production of antibiotic occur only in the upper levels of the digestive tract. Study of dixenic models wherein B. licheniformis was inoculated after Clostridium perfringens or Lactobacillus sp. or before Lactobacillus sp. revealed the simultaneous disappearance of B. licheniformis from the stomach and antibiotic from the feces. This strain persisted in the cecum, but only in the form of vegetative cells. These models demonstrate that the activity of the microflora in the upper segments can affect the equilibrium of the microflora throughout the digestive tract. Images

Translocation of strictly anaerobic bacteria from the intestinal tract to the mesenteric lymph nodes in gnotobiotic rodents

Viable cells of some strictly anaerobic strains belonging to Bacteroides, Clostridium and Fusobacterium genera were present in mesenteric lymph nodes of gnotobiotic rodents harbouring these strains. Various parameters were found to affect the incidence of translocation, including the caecal population level, the length of association with the host and the nature of the strains and host.

Évolution de la flore microbienne caecale après isolement chirurgical du gros intestin chez le porc

Summary An ileo-rectal anastomosis was created in growing pigs. The caecum and colon were left in place and their contents slowly emptied through a cannula located in the distal colon; accordingly, no food arrived in this caeco-colic compartment. Animals were slaughtered 14 to 54 days after the surgical operation. Using a quantitative differential analysis technique, the large intestine microflora were studied upon operation and at slaughter. It was observed that the number of strictly anaerobic bacteria did not vary or only slightly increased according to cell population counts. The most marked variations involved disappearance of the Lactobacillus population in all animals and disappearance of some morphological types of bacteria found in the dominant flora at the beginning of the experiment.

Implantation d'un mutant de Escherichia coli exigeant en acide diaminopimélique dans le tube digestif de souris gnotoxéniques

Summary A DAP − auxotroph mutant of Escherichia coli DP 50 requiring DAP and thymidine for growth was used as the receptor strain in genetic engineering. It failed to be implanted in axenic mice. However, when an inoculum containing more than 10 7 bacteria/ml was used, the DAP + reverse mutant devoid of requirement for DAP became implanted. When axenic mice were previously associated with Clostridium difficile containing DAP in the cell wall, the strain DAP − became implanted even when the inoculum was too small to permit implantation in axenic mice. Conversely, C. butyricum and C. perenne , whose cell walls also contain DAP, did not allow the establishment of a DAP − mutant. In animals associated with complex human flora without enterobacteria, neither of the 2 DAP − and DAP + mutants became implanted.