Isolement des bifidobacteries dans les selles apres ingestion prolongee de lait au bifidus (LB)

Review article: bifidobacteria as probiotic agents -- physiological effects and clinical benefits

Bifidobacteria, naturally present in the dominant colonic microbiota, represent up to 25% of the cultivable faecal bacteria in adults and 80% in infants. As probiotic agents, bifidobacteria have been studied for their efficacy in the prevention and treatment of a broad spectrum of animal and/or human gastrointestinal disorders, such as colonic transit disorders, intestinal infections, and colonic adenomas and cancer. The aim of this review is to focus on the gastrointestinal effects of bifidobacteria as probiotic agents in animal models and man. The traditional use of bifidobacteria in fermented dairy products and the GRAS ('Generally Recognised As Safe') status of certain strains attest to their safety. Some strains, especially Bifidobacterium animalis strain DN-173 010 which has long been used in fermented dairy products, show high gastrointestinal survival capacity and exhibit probiotic properties in the colon. Bifidobacteria are able to prevent or alleviate infectious diarrhoea through their effects on the immune system and resistance to colonization by pathogens. There is some experimental evidence that certain bifidobacteria may actually protect the host from carcinogenic activity of intestinal flora. Bifidobacteria may exert protective intestinal actions through various mechanisms, and represent promising advances in the fields of prophylaxis and therapy.

Genetic marking of Lactococcus lactis shows its survival in the human gastrointestinal tract

A human feeding study was performed with Lactococcus lactis TC165.5, which is genetically marked by insertion of the sucrose-nisin conjugative transposon Tn5276 and chromosomal resistance to rifampin and streptomycin. The fate of strain TC165.5 and its nucleic acids was monitored by conventional plating methods and by molecular detection techniques based on specific PCR amplification of the nisin (nisA) gene from DNA extracted from human feces. A method was developed for the efficient extraction of microbial DNA from human feces. The results show that a fraction of viable cells of L. lactis TC165.5 survived passage through the human gastrointestinal tract. Only cells that passed within 3 days of ingestion could be recovered from the feces of the volunteers, and they accounted for approximately 1% of the total number of cells consumed. The presence of nisA in DNA extracted from feces could be detected up to 4 days, when viable cells were no longer present.

Potential of using lactic acid bacteria for therapy and immunomodulation in man

There is in 1993 no proven medical indication of lactic acid bacteria (LAB) for therapy or immunomodulation in man. However, within the bulk of publications, rigorous trials have now opened rational fields of research on beneficial effects of LAB. These include lactose digestion, cholesterol metabolism, diarrheal disorders, prophylaxis of intestinal or urogenital infections, immunomodulation or even oral vaccination. We try here to analyse these studies, considering LAB as pharmacological agents, and conclude that pursuit of research could be promising for ecological therapy of mucosal diseases, and for development of original and flexible vectors for targeting in the gastrointestinal tract.

Fecal recovery in humans of viable Bifidobacterium sp ingested in fermented milk

Bifidobacterium sp is a natural component of the dominant colonic microflora that was recently introduced into several fermented dairy products. The aim of the present study was to study the fate of this microorganism in the human gut. On the basis of antibiotic resistance characters, a variant of Bifidobacterium sp that could be distinguished from indigenous bifidobacteria in the fecal flora was selected, and its survival and colonization in the colon was examined. This strain was used to ferment milk, and 125 g of the fermented product obtained was ingested by eight healthy volunteers three times daily for 8 days. Stools were recovered and weighed throughout the study. The results showed that the exogenous Bifidobacterium sp appeared in the stools and reached a mean level of 8.8 +/- 0.1 log colony-forming units per gram. This level was maintained as long as the fermented dairy product was consumed. When its ingestion stopped, the exogenous Bifidobacterium sp gradually decreased and was no longer detectable 8 days after cessation. The mean recovered quantity during the 8-day period of administration of the ingested bifidobacteria excreted in stools was 12.1 +/- 0.1 log colony-forming units per gram, i.e., 29.7% +/- 6% of the ingested bacteria, which was similar to the percentage that reached the colon in previous studies. It is concluded that under physiological conditions, exogenously administered Bifidobacterium sp do not colonize the human colon. However, the high fecal concentrations of exogenous bifidobacteria reached are compatible with metabolic "probiotic" activities.