Probiotic
Antagonistic activities of lactobacilli and bifidobacteria against microbial pathogens
Servin A.L.
The gastrointestinal tract is a complex ecosystem that associates a resident microbiota and cells of various phenotypes lining the epithelial wall expressing complex metabolic activities. The resident microbiota in the digestive tract is a heterogeneous microbial ecosystem containing up to 1¤1014 colony-forming units (CFUs) of bacteria. The intestinal microbiota plays an important role in normal gut function and maintaining host health. The host is protected from attack by potentially harmful microbial microorganisms by the physical and chemical barriers created by the gastrointestinal epithelium. The cells lining the gastrointestinal epithelium and the resident microbiota are two partners that properly and/or synergistically function to promote an efficient host system of defence. The gastrointestinal cells that make up the epithelium, provide a physical barrier that protects the host against the unwanted intrusion of microorganisms into the gastrointestinal microbiota, and against the penetration of harmful microorganisms which usurp the cellular molecules and signalling pathways of the host to become pathogenic. One of the basic physiological functions of the resident microbiota is that it functions as a microbial barrier against microbial pathogens. The mechanisms by which the species of the microbiota exert this barrier effect remain largely to be determined. There is increasing evidence that Lactobacilli and Bifidobacteria, which inhabit the gastrointestinal microbiota, develop antimicrobial activities that participate in the host's gastrointestinal system of defence. The objective of this review is to analyze the in vitro and in vivo experimental and clinical studies in which the antimicrobial activities of selected lactobacilli and bifidobacteria strains have been documented.
FEMS Microbiol Rev. 2004 Oct;28(4):405-40
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Microbial-gut interactions in health and disease. Probiotics.
Isolauri E., Salminen S, Ouwehand A.C.
The definition of probiotics has evolved from a live active culture which improves the balance of the gut microbiota composition to specific effects, in particular, the immunomodulatory potential of clearly defined strains. The strains with beneficial properties, potential sources of probiotics, most frequently belong to the genera Bifidobacterium and Lactobacillus, and some of these strains exhibit powerful anti-inflammatory properties. Indeed, probiotic therapy has attracted research interest in human infectious, inflammatory and allergic disease. The most fully documented disease altering the gut microbiota is acute infectious diarrhoea in childhood. Current probiotic research aims to provide safe but sufficient bacterial stimulus in order to avert deviant immune responsiveness related to allergic and inflammatory diseases. However, further rigorous scientific efforts are required to characterize the immunomodulatory potential of specific probiotic strains for these targets.
Best Pract Res Clin Gastroenterol. 2004 Apr;18(2):299-313.
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Antimicrobial susceptibility of bifidobacteria
Moubareck C., Gavini F., Vaugien L., Butel M.J., Doucet-Populaire F.
OBJECTIVES: The aim of our study was to analyse the antibiotic susceptibility of various strains of Bifidobacterium spp. to a wide range of antimicrobial agents.
METHODS: Fifty strains belonging to eight species of bifidobacteria, isolated from humans, animals or probiotic products, were tested for susceptibility to 30 antibiotics by disc diffusion on Brucella agar supplemented with 5% laked sheep blood and vitamin K1 (1 mg/L). MICs of nine anti-anaerobe agents, including three new molecules (telithromycin, linezolid and gatifloxacin), were determined using the reference agar-dilution method.
RESULTS: All strains of bifidobacteria, whatever the species, were sensitive to penicillins: penicillin G, amoxicillin (MIC50 0.06 mg/L), piperacillin, ticarcillin, imipenem and usually anti-Gram-positive antibiotics (macrolides, clindamycin, pristinamycin, vancomycin and teicoplanin). Susceptibility to cefalothin and cefotetan was variable. Most isolates (70%) were resistant to fusidic acid. As expected, high resistance rates were observed for aminoglycosides. Metronidazole, an agent known for its anti-anaerobe activity, was ineffective against 38% of the strains. The newly commercialized molecules, telithromycin, linezolid and gatifloxacin, were active with MIC50S of 1 mg/L. The only variation in susceptibility observed among the different species concerned Bifidobacterium breve, which appeared to be generally more resistant. Potentially acquired resistance was only observed against tetracycline and minocycline, in 14% of the strains.
CONCLUSIONS: With regard to a general concern about the safety of probiotics, such as potential transferability of resistance determinants, Bifidobacteria, with their low natural and acquired resistance to 30 antibiotics, appear risk-free.
J Antimicrob Chemother. 2004 Dec 1
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Screening of dairy yeast strains for probiotic applications
Kumura H., Tanoue Y., Tsukahara M., Tanaka T., Shimaza
To evaluate the potential of yeasts of dairy origin as probiotics, we tested 8 species including Candida humilis, Debaryomyces hansenii, Debaryomyces occidentalis, Kluyveromyces lactis, Kluyveromyces lodderae, Kluyveromyces marxianus, Saccharomyces cerevisiae, and Yarrowia lipolytica, isolated from commercial blue cheese and kefir. Strains were randomly selected from each species and tested for their ability to adhere to human enterocyte-like Caco-2 cells in culture. Among the 8 species, K. lactis showed higher adhesive ability than K. marxianus, K. lodderae, and D. hansenii. The other 4 species were poorly adhesive. All species other than K. marxianus and C. humilis were resistant to acidic conditions. In the presence of bile acid, growth inhibition was undetectable when incubation was carried out at 27 degrees C; however, it was evident for C. humilis and a strain of D. occidentalis when incubated at 37 degrees C. Moreover, the influence of proteinase treatment of living cells of K. lactis and K. lodderae on their adhesion to Caco-2 cells was evaluated. Although a slight reduction was recognized when K. lactis was treated with proteinase K, the influence of intestinal protease treatments of pepsin followed by trypsin was negligible. These results indicated that a proteinaceous factor was unlikely to be involved in adhesion of K. lactis and K. lodderae to Caco-2 cells. No stimulation of IL-8 synthesis by Caco-2 cells was recognized in the presence of K. lactis.
In conclusion, K. lactis was the most attractive to continue study for use as probiotic microorganisms.
J Dairy Sci. 2004 Dec;87(12):4050-6.
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When microbe meets human
Reid G.
Microbes make up a significant component of the human body, yet relatively little is known about how they influence health and disease. They colonize after birth by chance and circumstance, yet play a major role in immunity, digestion, and protection against disease. In relatively recent times, basic science and clinical studies have clearly shown the potential impact of indigenous and exogenous microbes on human health and well-being. Yet regulatory bodies, research funding agencies, and health care practitioners, perhaps disillusioned by too many unreliable, overhyped products that are marketed under the guise of probiotics or natural therapeutics, have lagged far behind in embracing this avenue of enquiry. As more scientifically proven probiotic products differentiate themselves from untested and unproven cure-alls, and as multidisciplinary research groups piece together the diverse components of the puzzle, humans will slowly begin to understand how best to optimize their coexistence with microbial organisms, thus perhaps prolonging and enhancing life.
Clin Infect Dis. 2004 Sep 15;39(6):827-30.
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Probiotics in gastroenterology: indications and future perspectives
Goossens D., Jonkers D., Stobberingh E., Bogaard, A. van den, Russel M., Stockbrügger R.
Nowadays. there is a growing interest in probiotics as a safe way of changing the intestinal bacterial flora. Probiotics may have potential in several gastroenterological conditions, especially when the intestinal flora has been disturbed.
Most scientific evidence is available for diarrhoea patients treated with Lactobacillus GG, Lactobacillus reuteri or
Saccharomyces boulardii. Meta-analyses have shown an overall reduction in the risk of antibiotic-associated diarrhoea during treatment with probiotics, and benefits have also been demonstrated for patients with rota-virus-associated diarrhoea. Patients with inflammatory bowel disease, an inflammatory disorder characterized by a change in the intestinal flora, are another important target group for which probiotics may be beneficial. It has been claimed that in ulcerative colitis and Crohn disease patients, lactobacilli, S. boulardii and Escherichia coli reduce relapses. But most studies were not placebo-controlled. A reduction in relapses has also been demonstrated in pouchitis patients treated with a multispecies probiotic. Irritable bowel syndrome might be another clinical indication for probiotic therapy, but results of clinical trials performed in these patients are inconsistent. Additionally, probiotics may improve lactose absorption. Helicobacter pylori eradication and constipation. Finally, in animal models of colorectal cancer, treatment with probiotics reduces the prevalence of this disease, and in humans the amount of genotoxic substances in faeces has
been reduced.
In conclusion, the results of studies on the effects of probiotics in gastrointestinal conditions are encouraging. But well-designed placebo-controlled studies are warranted before recommendations for therapeutic or preventive use can be given. Many issues still have to be resolved, including optimal dose and duration of treatment, selection of and differences between the several available probiotic strains, and, importantly, their mechanisms of actions have to be elucidated.
Scand J Gastroenterol Suppl. 2003;(239):15-23.
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Tolerance of probiotics and prebiotics
Marteau P, Seksik P.
The clinical efficacy of probiotics and prebiotics has been proved in several clinical settings. The authors review their proved or potential side effects. Probiotics as living microorganisms may theoretically be responsible for 4 types of side effects in susceptible individuals: infections, deleterious metabolic activities, excessive immune stimulation, and gene transfer. Very few cases of infection have been observed. These occurred mainly in very sick patients who received probiotic drugs because of severe medical conditions. Prebiotics exert an osmotic effect in the intestinal lumen and are fermented in the colon. They may induce gaseousness and bloating. Abdominal pain and diarrhea only occur with large doses. An increase in gastroesophageal reflux has recently been associated with large daily doses. Tolerance depends on the dose and individual sensitivity factors (probably the presence of irritable bowel syndrome or gastroesophageal reflux), and may be an adaptation to chronic consumption.
J Clin Gastroenterol. 2004 Jul;38(6 Suppl):S67-9.
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Probiotic consumption does not enhance the cholesterol-lowering effect of soy in postmenopausal women
Thomas W., Wangen K.E., Nettleton J.A., Kurzer M.S.,Greany K.A.
Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA.
Numerous studies report that soy lowers cholesterol. Probiotic bacteria were also reported to lower total cholesterol (TC) and LDL cholesterol (LDL-C). We hypothesized that by altering intestinal microflora, probiotic consumption may also change phytoestrogen metabolism and enhance the effects of soy.
To evaluate the independent and interactive effects of probiotic bacteria and soy on plasma TC, LDL-C, HDL cholesterol (HDL-C), and triglycerides (TG), 37 women with a baseline TC of 5.24 mmol/L were given the following 4 treatments for 6 wk each in a randomized crossover design: soy protein isolate (26 +/- 5 g soy protein containing 44 +/- 8 mg isoflavones/d); soy protein isolate + probiotic capsules (10(9) colony-forming units Lactobacillus acidophilus DDS-1 and Bifidobacterium longum); milk protein isolate (26 +/- 5 g milk protein/d); and milk protein isolate + probiotic. Soy consumption decreased plasma TC by 2.2% (P = 0.02) and LDL-C by 3.5% (P = 0.005), increased HDL-C by 4.2% (P = 0.006) and tended to decrease TG (P = 0.07) compared with milk protein intake. When divided according to initial TC concentration, soy effects were observed only in hypercholesterolemic women (TC > 5.17 mmol/L). In this subgroup, soy treatments decreased plasma TC by 3.3% (P = 0.01), LDL-C by 4.5% (P = 0.004), and TG by 10.6% (P = 0.02), and increased HDL-C by 4.2% (P = 0.02). When subjects were divided on the basis of plasma and urine concentrations of the isoflavone metabolite, equol, equol producers and nonproducers did not differ in baseline lipids or in the effects of soy.
Probiotics did not lower cholesterol or enhance the effects of soy. These results confirm a beneficial effect of soy on plasma cholesterol in mildly hypercholesterolemic postmenopausal women independent of equol production status, but do not support an independent or additive effect of these particular probiotic bacteria.
J Nutr. 2004 Dec;134(12):3277-83.
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