The strains of Bifidobacterium spp. highly resistant to βAlactams, macrolides, and aminoglycosides were isolated by using the gradient plate and broth culture methods with ampicillin, cephalexin, erythromycin, and kanamycin as selective agents. The biochemical characteristics, cell morphology, and antigenic structure of the mutants were similar to those of their original strains, except for the possession of antibiotic resistance. We think this is the first report on the existence of β -lactam- or macrolide-resistant strains from the genus Bifidobacterium.

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A cell wall preparation (whole peptidoglycan, WPG) derived from Bifidobacterium infantis exhibited antitumor activity when WPG and Meth A cells were mixed and injected subcutaneously (suppression test) in flora-bearing (FB) BALB/c mice. This antitumor activity was markedly reduced when the germfree (GF) BALB/c mice were used as a host. Histological examination of the injected site revealed vigorous polymorphonuclear leukocyte (PMN) infiltration and tumor cell degeneration at day 1 to 3 postimplantation of WPGMeth A mixture in both FB and GF mice, but later on re-appearance of tumor cell mass was seen in many GF but in only a few FB mice. Similar but somewhat weaker suppressive effects of WPG were seen in FB athymic nu/nu mice in which severe PMN infiltration was also developed. Results indicated that the early inflammatory reaction composed mostly of PMN played a role as the major effector mechanisms in the suppression test, and inferior antitumor activity of PMN from GF mice to that from FB mice was implicated. However, since FB euthymic but not FB nu/nu mice showed development of antitumor immunity in re-implantation, involvement of immunological capacity might have played an additional role in the suppression efficiency.

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Effects of a high cholesterol (HC) diet and HC diet supplemented with polydextrose on fecal flora, fecal bacterial enzyme activity and fecal putrefactive products in eight healthy volunteers were studied. They were fed a low cholesterol (LC) diet, HC diet, HC diet supplemented with polydextrose (15 g/day) (HCP) at 2-week intervals consecutively for 6 weeks. Polydextrose supplementation increased fecal weight and decreased fecal pH and the stool concentration of indole, p-cresol, iso-valeric acid and iso-butyric acid. A significant reduction of Clostridium in the feces was also observed during the HCP diet period. The frequency of occurrence and number of Clostridium perfringens in the feces were lower for the HCP diet than for the HC diet.

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Studies of oligosaccharides have recently become common, especially in Japan. This has been because of findings of marked biofunctions and usefulness of fructooligosaccharides (FOS) for human health due to their effect of improving the intestinal microflora. In this paper, we demonstrate several useful characteristics of FOS such as cholesterol reduction, suppression of putrefaction, normalization of microbial disorders of the colon and alleviation of constipation in clinical studies. It seems that the usefulness of FOS is related to the proliferation of bifidobacteria and other saccharolytic intestinal bacteria and also short chain fatty acids produced by these organisms.

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