Effects of a synbiotic milk product on human intestinal ecosystem.

AIMS: To investigate the effect of prolonged consumption of a synbiotic milk (Synbiotic) containing Lactobacillus acidophilus (strain 74-2, 10(7) CFU ml(-1)), Bifidobacterium lactis (strain 420, 10(7) CFU ml(-1)) and 2% inulin on colonic ecosystem in healthy humans. METHODS AND RESULTS: A group of 26 healthy subjects, aged 22-47 years, participated in a 6-week placebo-controlled dietary intervention study. After a 2-week baseline period, in which all volunteers consumed 500 ml day(-1) of 2% skimmed milk (Placebo), the study was designed as a randomized, double-blind, two-armed parallel study in which 4-week consumption of 500 ml day portions of Synbiotic or Placebo were compared. Faecal microbial counts, pH, l-lactic acid and bile acid concentrations were assessed before and after the intervention. Synbiotic consumption significantly decreased faecal dry weight (P < 0.01) and l-lactic acid (P < 0.05) concentration, while significantly increased faecal bifidobacteria (P < 0.05) and lactobacilli (P < 0.01) counts. CONCLUSION: The tested synbiotic milk showed its synbiotic nature by enhancing the growth of bifidobacteria and lactobacilli. SIGNIFICANCE AND IMPACT OF THE STUDY: Scientific support to functional effect of a synbiotic milk.

Behaviour of the pharmaceutical probiotic preparation VSL#3 in human ileostomy effluent containing its own natural elements.

The pharmaceutical probiotic VSL#3 (300 billion cfu/g lactic acid bacteria & bifidobacteria) was inoculated into human ileostomy effluent (HIE) to assess its behaviour vs the ileo-caecal tract. Separately, yogurt bacteria (yog) and bifidobacteria (Bif) present in VSL#3 were also inoculated into HIE. During 37 degrees C incubation (anaerobic condition) at zero, six and 24 hours, both cell growth in control HIE and indigenous Bif growth in HIE+yog were observed. Cells remained viable and metabolically active as shown by the increase in L(+) lactic acid in HIE+VSL#3 and HIE+yog and the pH decreased (approx. 5.5 compared with the 6.2 of control HIE). Total SCFA Short Chain Fatty Acids decreased in HIE+yog and HIE+VSL#3 at 6h and in all cultures at 24h; butyric acid decreased in HIE+Bif and HIE+VSL#3. Generally in vivo the bacteria remain in the ileo-caecal tract no longer than six h, therefore VSL#3 bacteria seem able to pass this barrier viably, colonizing the large bowel.

Effect of consumption of a ready-to-eat breakfast cereal containing inulin on the intestinal milieu and blood lipids in healthy male volunteers.

OBJECTIVE: To investigate the effect of a breakfast cereal containing inulin on blood lipids and colonic ecosystem in normolipidemic young men. SETTING: Department of Food Science and Microbiology,University of Milan, Italy. SUBJECTS: Twelve healthy male volunteers, age 23.3 +/- 0.5 y, body mass index (BMI) 25.7 +/- 1.2 kg/m2 (mean +/- s.e.m.). INTERVENTIONS: Subjects consumed daily, for three periods of four weeks, 50 g of a rice-based ready-to-eat cereal (placebo) and the same cereal containing 18% inulin (test) in substitution of their habitual breakfast, then returned to the habitual diet (wash-out). They followed no other dietary restrictions. RESULTS: No changes in body weight, dietary habits, faecal and bile acid output, faecal short-chain fatty acid (SCFA) and faecal pH, were observed at the end of each period, whereas plasma total cholesterol and triacylglycerols significantly decreased at the end of test period by 7.9 +/- 5.4 (P < 0.05) and 21.2 +/- 7.8% (P < 0.005) respectively. Meal glucose tolerance test (MTT) resulted in the same incremental area under the curve for both cereals (IAUC test 124 +/- 35; placebo 118 +/- 33 mmol x min/l, ns). Inulin markedly enhanced breath H2 excretion (IAUC test 280 +/- 40; placebo 78 +/- 26 ppm x h, P < 0.005), as well as faecal concentration of L-lactate. Total facultative anaerobes significantly decreased after test, and bifidobacteria increased after correction for total anaerobes (P < 0.05). Changes in blood lipids were negatively correlated with bifidobacteria counts and positively with secondary bile acid excretion (P < 0.05). CONCLUSIONS: Inulin seems to have a lipid lowering potential in normolipidemic men possibly mediated by mechanisms related to colonic fermentation.

Methanogenic bacteria: presence in foodstuffs.

Methanogenic bacteria are anaerobic, oxygen-intolerant microorganisms, and it is only by studying the different habitats of such bacteria that fundamental information about their ecology becomes available. This research has evaluated methanogenic bacteria in apparently aerobic ecosystems, in foodstuffs not subjected to chemical-physical reclamation processes, where the presence of methanogenic bacteria has never been investigated. Methanogenic bacteria, ascribable to the Methanogenium, Methanobacterium and Methanosarcina genera, were found in vegetables, meat, fish and cheese but were generally absent in confectionery products and fruit. The microorganisms appear to be chance contaminants, usually being present in only very low numbers. It should be noted that none of the tested foods showed the presence of Methanobrevibacter smithii, M. oralis or Methanosphaera stadtmaneae, methanogenic bacteria sometimes present in the human digestive tract.

Antimicrobial susceptibility tests on anaerobic oral mixed cultures in periodontal diseases.

The ecosystem of the dental plaque in periodontal diseases is very complex: the study of such micro-organisms, which are mostly strict anaerobes, requires the use of specific techniques under conditions of strict anaerobiosis. The aim of the present study was to design a rapid method to evaluate the activity of antimicrobials on mixed bacterial plaque of subjects with periodontal diseases. The study was carried out using a computerised instrument generally used for simultaneous diagnostic tests with aerobic bacteria. Operative and methodological modifications were made to obtain conditions of strict anaerobiosis and the balanced growth of all the microbial forms present in the mixed cultures of the plaque. Penicillins and cephalosporins were active on all the samples, whereas colistin, gentamicin, kanamycin and nalidixic acid showed no activity. Clindamycin, tetracycline, erythromycin and penicillin G were effective only against some samples. The activity of the antimicrobials towards isolated strains was analogous to that towards the corresponding mixed culture.

Intestinal methanogenic bacteria in children of different ages.

Faecal samples from children between 3 months and 5 yrs were investigated for the presence of methanogenic bacteria. Methanobacteria were not detected in faecal samples obtained from children under 27 months of age. At 27 months only one subject harbored methanobacteria; the number of methanobacteria hosts subsequently increased with age, with an incidence of 40% at 3 years and 60% at 5 years. The appearance of methanobacteria was not directly related to introduction of particular foods in the child's diet, which after 2 years becomes similar to that of Italian adults. These dietary changes could give rise to some physical-chemical modifications of the enteric lumen thus causing the conversion of the intestinal flora to an adult pattern and, in most subjects, the development of methanobacteria.

Human intestinal methanogens and lactulose administration.

The effect of lactulose on human intestinal methanogenic bacteria in ten subjects on lactulose therapy and ten control adults was evaluated. Methanogens were found in 90% of the population examined (9 treated subjects and 9 controls). A marked variability in methanogen number (ranging from 10(3)-10(10)/gdw) was observed in lactulose-treated subjects and in controls. Analysis of variance showed no significant difference between the two groups.

A study on the mechanism of the epimerization at C-3 of chenodeoxycholic acid by Clostridium perfringens.

The mechanism of 3-hydroxy epimerization of chenodeoxycholic acid by Clostridium perfringens was investigated in 3 alpha, 7 alpha-dihydroxy-[2,2,4,4-2H4]-, 3 alpha, 7 alpha-dihydroxy-[3 beta-2H]- and 3 beta, 7 alpha-dihydroxy-[3 alpha-2H]-5 beta-cholanoic acid transformations. Our findings rule out a dehydration-rehydration pathway and agree with a redox mechanism involving 3-oxochenodeoxycholic acid as intermediate.

[7-Alpha dehydroxylation of bile acids by O2-intolerant anaerobic intestinal microorganisms]. / 7 alpha-Deossidrilazione in vitro degli acidi biliari da parte di microrganismi intestinali anaerobi O2 non tolleranti.

The 7 alpha-dehydroxylation of cholic and chenodeoxycholic acids by mice intestinal microorganisms was studied. When all techniques, from autopsy of the animals to final incubation, are performed in oxygen-free environment, it has been found that anaerobic O2 non tolerant microorganisms might be considered the main responsible for these transformations.