Title
Probiotics, cecal microflora, and aberrant crypts in the rat colon.
Author
Gallaher DD; Stallings WH; Blessing LL; Busta FF; Brady LJ
Source
J Nutr, 1996 May, 126:5, 1362-71
Abstract
Our hypothesis was that administration of bifidobacteria, Lactobacillus acidophilus or both to rats will minimize the numbers of aberrant crypts in the distal colon that develop in response to the carcinogen 1,2-dimethylhydrazine (DMH). A series of experiments was designed to test this hypothesis where the treatments used were as follows: skim milk controls (Skim-Basal), skim milk + bifidobacteria (Bifido-Basal), skim milk + fructooligosaccharide (Skim-FOS), and skim milk + bifidobacteria + fructooligosaccharide (Bifido-FOS). In two experiments, bifido-bacteria + FOS administration significantly decreased the number of aberrant crypts that developed, but there was no clear relationship of aberrant crypts to numbers of bifidobacteria or Clostridium perfringens. In the third experiment, the Bifido-FOS treatment led to significantly fewer aberrant crypts and aberrant crypt foci than the Bifido-Basal treatment. The Skim-FOS group had significantly more cecal bifidobacteria than the Skim-Basal group and significantly fewer C. perfringens than the Skim-Basal and Bifido-Basal. In a fourth experiment, L. acidophilus was added as an additional treatment. The number of aberrant crypts was not significantly different among the groups. However, the number of C. perfringens was significantly decreased by the addition of bifidobacteria, L. acidophilus or the combination of the two, whereas the numbers of bifidobacteria and L. acidophilus were not affected by treatment. A significant correlation (R2 = 0.84, P < 0.01) was noted between the body weight of rats at DMH administration and the magnitude of the difference in aberrant crypts between the Skim-Basal rats and the Bifido-FOS rats. The results suggest that there is variability in the effects of bifidobacteria and L. acidophilus administration on both aberrant crypt formation and C. perfringens.

Title
Effect of bifidobacteria on nitrites and nitrosamines.
Author
Grill JP; Crociani J; Ballongue J
Source
Lett Appl Microbiol, 1995 May, 20:5, 328-30
Abstract
The effects of six different bifidobacteria strains were studied on two procarcinogens: nitrite and nitrosamines. Growth of bifidobacteria was not affected by nitrite concentrations below 50 mumol l-1. At nitrite concentrations greater than 2000 mumol l-1, total growth inhibition was observed. Nitrite elimination by a non-enzymic mechanism was noted for six strains of bifidobacteria. Acids produced by the bacteria seem to be involved in nitrite elimination. Nitrosamines tested had no effect on growth of bifidobacteria. Only one strain (Bifidobacterium longum BB 536) was able to metabolize nitrosamines by an intracellular mechanism.

Title
Regulatory effects of bifidobacteria on the growth of other colonic bacteria.
Author
Gibson GR; Wang X Address MRC Dunn Clinical Nutrition Centre, Cambridge, UK.
Source
J Appl Bacteriol, 1994 Oct, 77:4, 412-20
Abstract
In the human large intestine bifidobacteria are a numerically important group of micro-organisms which are considered to exert a range of biological activities related to host health. One aspect is the inhibitory effect of these bacteria on other species, possibly excluding long term colonization by invasive pathogens. It has been suggested that the mechanism of inhibition carried out by bifidobacteria is related to the fermentative production of acids such as acetate and lactate. Experiments reported in this paper attempted to address this theory. Co-culture experiments whereby Bifidobacterium infantis was incubated with Escherichia coli and Clostridium perfringens, in a variety of fermentation systems, indicated that the bifidobacterium was able to exert an inhibitory effect not necessarily related to acid production. Further studies showed that eight species of bifidobacteria could variously excrete an anti-microbial substance with a broad spectrum of activity. Species belonging to the genera Salmonella, Listeria, Campylobacter and Shigella, as well as Vibrio cholerae, were all affected. These results show that bifidobacteria are able to exert more than one mechanism of inhibition, which may be of some importance with regard to protection against gastroenteritis.
Title
Bifidobacteria strain behavior toward cholesterol: coprecipitation with bile salts and assimilation.
Author
Tahri K; Grill JP; Schneider F
Source
Curr Microbiol, 1996 Sep, 33:3, 187-93
Abstract
Resting cells and growing cells of bifidobacteria strains exhibited an ability to remove cholesterol in the presence of bile salts. In resting cell assays, the removed cholesterol was precipitated in the presence of cholic acid at pH values lower than 5.4. However, this precipitated cholesterol was redissolved when the pellets were washed with phosphate buffer, pH 7, and no cholesterol was found in the cells. It appears that this precipitation is a transient phenomenon. In the case of growing cells, the removed cholesterol was partially recovered when cells were washed with phosphate buffer, pH 7, while the remaining cholesterol was extracted from the cells. Cultured in the presence of radiolabeled free or esterified cholesterol, bifidobacteria strains were able to assimilate esterified cholesterol. It is concluded that the removal of cholesterol from the growth medium by bifidobacteria strains is due to both bacterial assimilation and precipitation of cholesterol.

Title
Effects of fructo-oligosaccharides ingestion on fecal bifidobacteria and selected metabolic indexes of colon carcinogenesis in healthy humans.
Author
Bouhnik Y; Flourié B; Riottot M; Bisetti N; Gailing MF; Guibert A; Bornet F; Rambaud JC
Source
Nutr Cancer, 1996, 26:1, 21-9
Abstract
Fructo-oligosaccharides (FOS) are a mixture of oligosaccharides consisting of glucose linked to fructose units. They are not digested in the human small intestine but fermented in the colon, where they could specifically promote the growth of some species of the indigenous microflora, especially bifidobacteria. We assessed in healthy humans the effects of FOS ingestion in fecal bifidobacteria and selected metabolic indexes potentially involved in colonic carcinogenesis. Twenty volunteers randomly divided into two groups were studied for three consecutive 12-day periods. During the ingestion period, they received 12.5 g/day FOS or placebo (saccharose) in three oral doses. Stools were regularly collected and analyzed. FOS ingestion led to an increase in fecal bifidobacterial counts [7.9 +/- 0.5 to 9.1 +/- 0.3 (SE) log colony-forming units/g wet wt, p < 0.01] and beta-fructosidase activity (9.6 +/- 1.9 to 13.8 +/- 1.9 IU/g dry wt, p < 0.01). In contrast, FOS ingestion had no significant effect on fecal total anaerobes, pH, the activities of nitroreductase, azoreductase, and beta-glucuronidase, and the concentrations of bile acids and neutral sterols. We conclude that ingestion of FOS, at a clinically tolerated dose of 12.5 g/day, led to an increase in colonic bifidobacteria. This effect was not associated in healthy humans with beneficial changes in various factors potentially involved in the pathogenesis of colonic cancer.

Title
Bifidobacteria and probiotic effects: action of Bifidobacterium species on conjugated bile salts.
Author
Grill JP; Manginot Dürr C; Schneider F; Ballongue J
Source
Curr Microbiol, 1995 Jul, 31:1, 23-7
Abstract
The effect of six different conjugated bile salts (two trihydroxyconjugated bile salts: tauro and glycocholic acids; and four dihydroxyconjugated bile salts: tauro- and glycochenodeoxycholic, tauro- and glycodeoxycholic acids) on eight bifidobacteria strains were studied. A strong growth-inhibitory effect was observed (80% at 0.95 mM) for each bile salt and strain. This phenomenon was explained by the production of deconjugated bile salt during bifidobacteria growth. The deconjugation phenomenon was concurrent with biomass production, and deconjugated bile salts were the sole compound produced during bifidobacteria biotransformation. In resting cell experiments, differences appeared between the strains and the kind of bile salts, particularly concerning taurocholic acid. The Bifidobacterium longum strains were the most efficient among the bacteria tested.

Title
Impact of Bifidobacterium longum on human fecal microflora.
Author
Benno Y; Mitsuoka T
Source
Microbiol Immunol, 1992, 36:7, 683-94
Abstract
The effects of Bifidobacterium longum feedings for five weeks on the fecal microflora, water contents, pH values, ammonia concentration, and beta-glucuronidase activity were investigated in five healthy human volunteers. Although numbers of major bacterial groups of the fecal microflora were not changed by the bifidobacteria feedings, a remarkably decreasing number of lecithinase-negative clostridia was observed. The percentage of lecithinase-negative clostridia and bacteroides to the total bacterial numbers isolated were decreased during the feedings and numbers of C. paraputrificum and C. innocuum were reduced. A significant reduction of fecal pH values for the last week of the feeding was observed. Ammonia concentration and beta-glucuronidase activity in the feces during the feedings were significantly lower than those before or after the feedings. The oral supplement of B. longum may be introduced to improve the fecal properties such as fecal ammonia concentration and beta-glucuronidase activity, but not the composition of fecal flora.

Title
Effects of three strains of bifidobacteria on cholesterol.
Author
Tahri K; Crociani J; Ballongue J; Schneider F
Source
Lett Appl Microbiol, 1995 Sep, 21:3, 149-51
Abstract
To determine the validity of the hypothesis of assimilation or precipitation of cholesterol by Bifidobacterium species, resting cell assays and cultures were undertaken in TPY medium containing oxgall. With resting cell assays (pH 5), cholesterol was precipitated and redissolved in phosphate buffer (pH 7). At the end of the cultures, only part of the removed cholesterol from the culture medium was found in the phosphate buffer, while the missing cholesterol was in cell extracts. It appeared that removal of cholesterol during culturing was not solely due to its precipitation. It is concluded that growing bifidobacteria cells are able to remove cholesterol both by precipitation and assimilation.

Title
Selective stimulation of bifidobacteria in the human colon by oligofructose and inulin.
Author
Gibson GR; Beatty ER; Wang X; Cummings JH
Source
Gastroenterology, 1995 Apr, 108:4, 975-82
Abstract
BACKGROUND/AIMS: Oligofructose and inulin are naturally occurring indigestible carbohydrates. In vitro they selectively stimulate the growth of species of Bifidobacterium, a genus of bacteria considered beneficial to health. This study was designed to determine their effects on the large bowel microflora and colonic function in vivo. METHODS: Eight subjects participated in a 45-day study during which they ate controlled diets. For the middle 15 days, 15 g.day-1 oligofructose was substituted for 15 g.day-1 sucrose. Four of these subjects went on to a further period with 15 g.day-1 inulin. Bowel habit, transit time, stool composition, breath H2 and CH4, and the predominant genera of colonic bacteria were measured. RESULTS: Both oligofructose and inulin significantly increased bifidobacteria from 8.8 to 9.5 log10 g stool-1 and 9.2 to 10.1 log10 g stool-1, respectively, whereas bacteroides, clostridia, and fusobacteria decreased when subjects were fed oligofructose, and gram-positive cocci decreased when subjects were fed inulin. Total bacterial counts were unchanged. Fecal wet and dry matter, nitrogen, and energy excretion increased with both substrates, as did breath H2. Little change in fecal short-chain fatty acids and breath CH4 was observed. CONCLUSIONS: A 15-g.day-1 dietary addition of oligofructose or inulin led to Bifidobacterium becoming the numerically predominant genus in feces. Thus, small changes in diet can alter the balance of colonic bacteria towards a potentially healthier microflora.

Title
Influence of galactooligosaccharides on the human fecal microflora.
Author
Ito M; Deguchi Y; Matsumoto K; Kimura M; Onodera N; Yajima T
Source
J Nutr Sci Vitaminol (Tokyo), 1993 Dec, 39:6, 635-40
Abstract
The effects of galactooligosaccharides intake on fecal microflora and their metabolism were investigated in twelve healthy volunteers, in whom the numbers of indigenous bifidobacteria are comparatively low. The galactooligosaccharides ingestion increased the number of bifidobacteria, but remarkable changes of other organisms were not observed. This sugar also lowered fecal nitroreductase activity, the concentrations of indole and isovaleric acid.