Summary -The development of a dairy Propionibacterium and its establishment in the gut were studied. Mice fed a convention al diet received a suspension of propionibacteria in skim milk provided in their water bottles for 7 d. Counts of propionibacteria in faeces and intestinal sections indicated that the strain used reached significant levels in the gut during treatment. They remained in high number 1 week after cessation of the diet. Their permanence in the gut could be related to an adhesion onto the intestinal mucosae. The presence of these bacteria in the intestine favourably affected the lipid metabolism and the immune system of mice. The effect on the serum lipids level was evaluated after feeding mice with 5 different diets, containing or not a supplementation of milk cream and propionibacteria. Total cholesterol, HDL, LDL and triglycerides were determined. The results showed that this strain tends to reverse the hyperlipemic effect of a diet with high lipid content. An increase both in the phagocytic activity of peritoneal macrophages and in the phagocytic function of reticuloendothelial system was observed on the 7th d of feeding. The activity decreased when mice returned to a conventional diet. The data confirm that sorne strains of dairy propionibacteria can develop in the gut and exert beneficial effects on the host.

The objective of this study was to determine the influence of administration of buffalo dairy products on lipid content and conjugated linoleic acid (CLA) incorporation on liver and intestine of mice. Buffalo cheeses were selected according to nutritional properties and CLA content. Cheeses were previously manufactured using as adjunct culture bacteria with probiotic or technological properties. BALB/c mice were fed for 28 days, and then a single dose of 1,2-dimethylhydrazine (DMH) as oxidant agent was administered before the influence of diet and DMH on antioxidant status in tissues was evaluated. Mice fed buffalo cheese showed the highest body weight gain (P < .05). Polyunsaturated fatty acid (PUFA) content in foods was very different, but total PUFA incorporation was similar in mouse tissues. CLA was only detected in fat tissues of mice fed dairy products, with cis-9, trans-11 being the major isomer. A higher linolenic (C(18:3)) acid content was found in tissues of mice fed commercial diet (control group), and it was partially replaced by CLA in groups receiving buffalo milk or cheese. Lipoperoxides (thiobarbituric acid-reactive substances) were higher in tissues of the control group with or without DMH administration, and DMH had a cytotoxic effect on colon cells (P < .05). Superoxide dismutase (SOD) and catalase activities in liver and intestine were similar among animals, with a slight increase of SOD detected after DMH treatment. Consumption of buffalo dairy products did not affect the oxidative status of mice tissues even after DMH application. In the present study, a protective effect of buffalo cheese and milk on intestine cells was determined.