[Comparative microbiological study of fresh and heat-treated yoghurt in an in vivo animal model]

In an acute assay, rats fasted for 24 h were sounded with 2 ml of fresh yogurt, sterilised yogurt or distilled water, and sacrificed at 2, 4, 8 and 24 h. They were compared with non-sounded rats. The survival of the lactic bacteria of the yogurt administered in the animals' stomach and intestines was determined, and the bacteria isolated were to the Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus profiles belonging to the strains isolated originally from the yogurt. Counts of the total number of microorganisms that were grown in lactobacilli and lactic streptococci media were also made. Analyses of the different types of resulting colonies in the lactobacilli and lactic streptococci media was performed. No L. delbrueckii subsp. bulgaricus or S. thermophilus were characterized in this acute assay. The statistical analysis of the results did not show significant differences in the log UFC. g-1, of the intestinal microbiota microorganisms of the three groups of animals in any of the times. In a chronic assay, three groups of animals, after 30 days of nourishment ad libitum with either a semisynthetic diet with 10% of fresh yogurt, or with 10% of sterilised yogurt or controls, housed in individual metabolism cells, were sacrificed. The results did not show meaningful differences in the long UFC. g-1 of the intestinal microbiota microorganisms from the three groups of animals in any of the times. In turn, in the study of the different types of colonies resulting in the lactobacilli and lactic streptococci media, no L. delbrueckii subsp. bulgaricus or S. thermophilus were characterised in this chronic assay. The results did not show meaningful differences in the log CFU. g-1 of the intestinal flora microorganisms from the three groups of animals in any of the times. In turn, no L. delbrueckii subsp. bulgaricus or S. thermophilus were characterised in this chronic assay.