Xylooligosaccharide was found to have a favorable effect on human intestinal flora. Xylooligosaccharide was utilized by bifidobacteria, but it was not utilized by Escherichia coli and Clostridium spp. in vitro. In vivo, xylooligosaccharide (5 g/day) promoted the growth of bifidobacteria, lowered fecal pH and helped to maintain the fecal water content within normal range. These results showed that xylooligosaccharide can selectively promote the growth of bifidobacteria and help to establish favorable environmental conditions in the intestines.

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The preparation of cells of Peyer's patches (PP) from mice and some immunological activities of the cells were examined. The PP cells were obtained with high yield (>1×10⁷/CDF₁ mouse) and viability (>97%), when the PP were cut and teased gently with two glasses in RPMI 1640 medium containing 5% heat-inactivated calf serum. The PP cells responded well to mitogens, and particularly the responses to a T cell mitogen, concanavalin A (Con A), were at similar levels to those of spleen cells. When the cells were stimulated with alloantigens in mixed lymphocyte reaction, significant response was observed. The PP cells cultured with lipopolysaccharide (LPS) exhibited polyclonal B cell responses (antigen-nonspecific increase in the number of antibody-producing cells). Furthermore, the levels of anti sheep erythrocytes (SRBC) plaque-forming cells (PFC) in PP cell cultures increased significantly when the PP cells were cultured with SRBC in vitro. However, the PP cells did not show the natural killer (NK) activity. These results showed that the PP cells obtained by the physical method described here contained functionable T and B lymphocytes and accessory cells.

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Streptococcal strains producing glycosyltransferase (GT) were surveyed from 15 fecal samples collected from 13 humans. In total, 219 strains showing marked mucoidicity were detected on the sucrose-containing Brain Heart Infusion plate medium. Twenty-two isolates, the most mucoid group, were selected for further examinations. All of them were identified as Streptococcus salivarius. The GT activity of some isolates, determined by the measurement of the incorporation of radioactivity into polysaccharides and oligosaccharides from [U^-14C] -sucrose, was considerably higher than that of a reference strain of S. salivarius (HHT). The major polysaccharide produced by the GTs of fecal isolates seemed to be fructan because the color of the spot produced on a thin-layer-chromatography plate, which did not migrate, was similar to that of levan. GTs acted in the contents of small intestine collected from rabbits, showing the possibility that they may normally act in the small intestine, where a large number of streptococci live as a member of normal flora.

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Bifidobacteria species or subspecies in cultured or culturecontaining milks is a presently approved way to offer beneficial effects for human health. The microorganisms should be still in a living stage at the time of consumption. Multiplication and viability of the anaerobic Bifidobacteria in milk require special efforts in production, handling and storage of this kind of products. It is possible to maintain the viability of Bifidobacteria in culture-containing milks, as there is no remarkable lowering of pH during shelf life. In cultured milks, however, (yoghurt-like products) the viability of Bifidobacteria is reduced to a higher degree, depending on the extent of acidification and the strains used. The range of decrease of colony-forming units (cfu) of 3-4 log₁₀ cycles may occur within 20 or even 5 days. There may still be some unknown facts concerning the irregular curve of counts. The survival of Bifidobacteria means living cells from ingestion should reach the adequate area of the intestinal tract of humans. That is still not verified sufficiently. Results from animals cannot be transferred to humans without limitations. Knowledge on humans is based mostly on well-founded suppositions and may be confirmed experimentally in more detail in the future. The identification of Bifidobacteria in milks is not too difficult in principle. Species which are used can be identified in a quite simple way, such as Bifidobacterium longum, breve, infantis, or even bifidum. Some difficulties may result with separation of Bifidob longum from Bifidob. animalis. Problems with isolating Bifidobacteria from milks may arise if a dominating lactic acid bacteria flora is present. No full selective media seems to have been explored up to now. Bifidobacteria counts lower than 10⁴/g may not be determined if total count comprises more than 10⁸/g.

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Mucus and gynolactose might control host-Bifidobacterium interactions. Their respective roles were investigated in this study using gnotobiotic mice. By comparing glycoprotein SDS-PAGE profiles, mucus from various murine lines (NC, CF₁, BALB/c and C₃H) were differentiated. We attempted then to determine the intestinal substrates utilized by various bifidobacteria. First, NC and CF₁ germfree mice received an inoculum of a murine species, B. animalis. Bacteria utilized the glycosyl fraction of several CF₁. glycocompounds. No such extensive degradation was observed in NC mice. In constrast, both NC and CF₁, mice responded to colonization by modifying hexosamine composition of their high molecular weight mucins. Three human species (B. bifidum, B. breve and B. longum) were then assayed for their in vivo capacity to degrade murine mucus from C3H mice. B. bifidum utilized extensively glycoproteins from the mucus, whereas B. longum and B. breve were unable to degrade them. However, none of the human strains led to intestinal mucins modification. Origin of the strains seemed to be a factor controlling the host response. Finally, gynolactose effect was investigated in germfree, B. breve-associated, and infant flora-associated C₃H mice. Few modifications to mucus composition were noticed in the first two cases. In infant floraassociated mice, new intestinal glycoproteins and proteins were detected but bacterial counts were not changed. Host response to gynolactose might depend on the implantation of some unknown intestinal bacteria. It is likely that the proliferation of bifidobacteria shown in breast-fed infants does not correspond to a direct gynolactose promoting effect. But it is probably related to mucus modification induced by gynolactose.

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Six antibiotic-resistant bifidobacteria (bif-R) strains were compared with each original strain by deoxyribonucleic acid (DNA) /DNA homology. The bif-R strains had extremely high levels of over 93% homology to each ³H-labeled original strain.

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After the previous administration with N-methyl-N'-nitro-N-nitrosoguanidine in drinking water, Wistar rats were fed 25 g/day of yoghurt on 4 days every week or a 20%-lactose-containing purified diet, and the incidence of gastrointestinal tumors in them was compared with that in their counterparts. The yoghurt-fed rats showed a significantly lower incidence of gastric tumors (50%) than the counterpart group (89%). Dietary lactose considerably suppressed the incidence of gastric tumors (10%) compared to the control diet (44%). These data support the epidemiological view that milk and milk products are protective against human gastric cancer.

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