The coming of age of probiotics

A New Probiotic Cheese with Antioxidative and Antimicrobial Activity

The aim of our study was to develop an original probiotic cheese based on the Estonian open-texture, smear-ripened, semisoft cheese "Pikantne." Cheese was produced by two methods using cheese starter cultures (Probat 505) in combination with 0.04% of probiotic Lactobacillus fermentum strain ME-3 (10(9) cfu/mL) with high antimicrobial activity and antioxidative properties. The probiotic Lactobacillus was added into milk simultaneously with starter cultures (cheese A) and into drained curd (cheese B). After addition of probiotic L. fermentum ME-3, the cheese composition, flavor, and aroma were comparable to the control cheese (score values = 4.5, 4.2, and 3.7 for control cheese, cheese A, and cheese B, respectively). Cheese A, which had good sensory properties, was chosen for further testing of viability and probiotic properties. The probiotic strain was found to withstand the technological processing of cheese, surviving and sustaining moderate antimicrobial and high antioxidative activity throughout ripening and storage (the ripened cheese contained approximately 5 x 10(7) cfu/g viable ME-3 cells), although the viability of the ME-3 strain incorporated into the cheese showed a slight decrease between d 24 and 54 after cheese preparation. Semisoft cheese "Pikantne" serves as a suitable carrier of antimicrobial and antioxidative L. fermentum ME-3.

Identification method based on PCR combined with automated ribotyping for tracking probiotic Lactobacillus strains colonizing the human gut and vagina

AIMS

A molecular methodology based on PCR-associated automated ribotyping was developed to specifically detect the Lactobacillus strains of two probiotic products (an orally administered lyophilized preparation and vaginal tablets) in human faeces and vaginal swabs.

METHODS AND RESULTS

The 16S-23S rDNA sequences and the ribotype profiles of the probiotic lactobacilli were characterized and new species-specific primer sets were designed. The identification of faecal and vaginal lactobacilli isolated from subjects administered with the probiotic products was performed by using PCR with species-specific primers followed by strain-specific automated ribotyping.

CONCLUSIONS

The PCR-ribotyping identification allowed to study the colonization patterns of the probiotic lactobacilli in the human gut and vagina evidencing the strains with the best survival capability.

SIGNIFICANCE AND IMPACT OF THE STUDY

The proposed molecular method represents a powerful tool of strain-specific identification, useful for differentiating exogenous from indigenous strains in any microbial ecosystem and for rationally choosing probiotic bacteria with the best chance of survival in the host.

Probiotics and inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterised by a chronic dysregulation of the inflammatory response in the gastrointestinal tract. While the pathogenesis is unclear, studies have demonstrated that the gastrointestinal tracts of patients with IBD are populated with increased levels of adherent and pathogenic bacteria. This evidence, combined with growing data accumulated from genetic studies as well as animal models of IBD, indicates that an aberrant response to altered enteric flora plays a significant role in the disease process. Current therapies for IBD have been directed towards the development of anti-inflammatory agents and immunomodulators to attenuate the inflammatory response in the gastrointestinal tract. Antibiotics are also partially effective in the treatment of IBD, presumably by altering the bowel flora. However, it is clear from clinical trials that immunomodulators and antibiotics are not effective in a large proportion of patients with IBD and other therapeutic alternatives need to be pursued. Probiotics are microbial supplements capable of recolonising the bowel with non-pathogenic strains of bacteria or yeast. Probiotics have long been shown to be beneficial in both infectious and non-infectious digestive disorders. Growing evidence indicates that probiotics may be effective in the treatment of specific clinical IBD conditions. This article addresses the current evidence for the role of enteric flora in the pathogenesis of IBD and the clinical evidence supporting the use of probiotics in specific clinical IBD conditions.

Fermentation of banana media by using κ-carrageenan immobilized Lactobacillus acidophilus

Fermentation media were prepared by using banana as the raw material, and cell immobilization of Lactobacillus acidophilus by kappa-carrageenan entrapment was applied to enhance the fermentation efficiency. Gel beads of diameters around 3.0 mm were prepared for the immobilized cells, ripe bananas were used for preparation of media, and both free and immobilized cells were employed to carry out the fermentation for 80 h. Cells leaked out from the gel beads and proliferated in the medium solution during the fermentation of immobilized cells. The final viable cell number reached 10(5) CFU/ml in the medium suspension, over 10(8) CFU/(ml gel) in gel beads for the immobilized cell fermentation and around 10(6) CFU/ml for the free cell fermentation. Immobilized cells withstand the adverse conditions in banana media resulting in better fermentation efficiency compared to free cells. Variation of fructooligosaccharides (FOS) in banana media was not significant in immobilized cell fermentation compared to free cell. Immobilized L. acidophilus fermented banana medium was found to possess synbiotic properties.

The suppressive effect of bifidobacteria on Bacteroides vulgatus, a putative pathogenic microbe in inflammatory bowel disease

Bacteroides, a predominant commensal bacteria in the gut, are thought to be responsible for the development of inflammatory bowel disease (IBD). In the present study, we examined whether or not bifidobacteria suppress B. vulgatus, a representative pathogenic Bacteroides species, in both the coculture system and the gnotobiotic murine model. As a result, Bifidobacterium infantis 1222 highly inhibited the growth of B. vulgatus in the coculture and also significantly suppressed the systemic antibody response raised by B. vulgatus colonizing the gut in gnotobiotic mice. Colonization of the mice by B. vulgatus increased the number of Peyer's patch (PP) cells bearing PNA (peanut agglutinin)+/anti-kappa+ phenotype, which represents plasma cell-like B cells. Moreover, treatment of those B. vulgatus-implanted mice with B. infantis 1222 abrogated such increase in the number of PNA+/anti-kappa+ cells. These results thus suggested that B. infantis 1222 protected the gut epithelial layer including the PP from being invaded by Bacteroides, thereby suppressing the systemic antibody response raised by Bacteroides.

Growth and metabolism of selected strains of probiotic bacteria in milk

Growth and metabolism of five probiotic strains with well-documented health effects were studied in ultra-high temperature (UHT) treated milk, supplemented with 0.5% (w/v) tryptone or 0.75% (w/v) fructose. The probiotic strains were Lactobacillus acidophilus La5, Lb. acidophilus 1748, Lactobacillus rhamnosus GG, Lactobacillus reuteri SD 2112 and Bifidobacterium animalis BB12. Fermentation was followed for 72 h at 37 degrees C and the samples were analysed for pH, log cfu ml(-1), volatile compounds, organic acids and carbon dioxide. The strains reduced pH from 6.7 to between 3.9 and 4.4 after 24 h of incubation. All strains attained viable cell counts above 8.7-9.18 log cfu ml(-1) after 6-16 h of incubation. The two Lb. acidophilus strains showed a stable level of viable cells during 12-72 h of incubation but the three other strains showed a reduction of 0.4-1.1 log cfu ml(-1) from 24 to 72 h of incubation. However, all strains showed cell levels between 7.8 and 8.7 log cfu ml(-1) after 72 h of incubation. After 48 h of incubation, the amount of lactic acid produced varied according to strain from 6949 to 14,000 mg kg(-1) and acetic acid produced varied from 0 to 6901 mg kg(-1). Three of the strains metabolised citrate but only low amounts of diacetyl and acetoin were detected within strains, 0.2-0.8 and 6.5-10 mg kg(-1), respectively. Carbon dioxide produced varied from 221 to 3942 mg kg(-1) and was connected to the citrate-fermenting ability of the strain used and their carbohydrate fermentation pathway. Three of the strains produced detectable levels of acetaldehyde and the concentration varied from 9.4 to 12.6 mg kg(-1) after 24 h of incubation. All five probiotic strains showed very different profiles of metabolites during fermentation; however, the two Lb. acidophilus strains were the most alike. Our findings show the importance of controlling the fermentation time since the probiotic strains produced different amounts of metabolic products according to fermentation time.

Transcript map of the temperate Lactobacillus gasseri bacteriophage ϕadh

Temporal transcription of phage ϕadh was analysed during lytic reproduction. Based on Northern hybridizations the phage genome was divided into regions of early, middle and late transcription. Eight groups of overlapping transcripts, probably originating from common precursors, were distinguished. Early transcription of a 10·9 kb region adjacent to the lytic/lysogenic switch started within the first 10 min of infection and produced three groups of mRNAs mostly related to DNA replication. Four middle transcripts were observed 30 min after infection, corresponding to an 8·5 kb genomic region, which started at the replication origin (ori) and encompassed a DNA packaging function and the cos site. Three groups of late transcripts were first observed 50 min after infection, corresponding to a 21·1 kb region between the middle region and the attachment site (attP), encoding functions for capsid morphogenesis and host cell lysis. A fourth group of late-appearing mRNAs was divergently transcribed from the 3·2 kb section between attP and the lytic/lysogenic switch, including the repressor and integrase genes. Except for one set of early mRNAs, all the transcripts persisted until the end of the reproduction cycle. Two confirmed and two predicted promoters were assigned to transcript 5′ ends in the early region.

Probiotic and milk technological properties of Lactobacillus brevis

Two Lactobacillus brevis strains ATCC 8287 and ATCC 14869(T), were evaluated for their applicability as putative probiotics in dairy products. The strains expressed good in vitro adherence to human Caco-2 and Intestine 407 cells and tolerated well low pH, bile acids and pancreatic fluid under in vitro conditions. In antimicrobial activity assays, strain ATCC 8287 showed inhibitory properties toward selected potential harmful microorganisms, particularly against Bacillus cereus. Both L. brevis strains were resistant to vancomycin, which is typical for the genus Lactobacillus. The L. brevis strains were not able to acidify milk to yoghurt but were suitable as supplement strains in yoghurts. This was shown by producing a set of yoghurt products and analysing their rheological and sensory properties during a cold storage period of 28 days. Survival of the strains through human intestine was examined in 1-week feeding trials. Despite its human origin, L. brevis ATCC 14869(T) could not survive through the gastrointestinal (GI) tract, whereas L. brevis ATCC 8287 was detected in the faecal samples taken during and immediately after ingestion of the strain. In conclusion, L. brevis ATCC 8287 is a promising candidate as a probiotic supplement in dairy products.

Probiotic properties of human lactobacilli strains to be used in the gastrointestinal tract

AIMS

The study of two human strains of Lactobacillus to be used as probiotics in the gastrointestinal tract.

METHODS AND RESULTS

The Lactobacillus acidophilus UO 001 and Lact. gasseri UO 002, were resistant to the gastrointestinal conditions (pH 2 and 3, presence of pepsin, pancreatin or bile salts), the resistance was enhanced in the presence of skimmed milk. Additionally, adhered to Caco-2 cells through glycoproteins in Lact. gasseri and carbohydrates in the case of Lact. acidophilus. These strains are able to inhibit the growth of certain enteropathogens: Salmonella, Listeria and Campylobacter without interfering with the normal microbiota of the gastrointestinal tract, as stated by using the mixed culture and the spot agar test. Finally, strongly adherent Lact. gasseri were found to inhibit the attachment of Escherichia coli O111 to intestinal Caco-2 cells under the condition of exclusion.

CONCLUSIONS

These results indicate that the two strains of Lactobacillus from human origin present important properties for survival in, and colonization of, the gastrointestinal tract, that give them potential probiotic.

SIGNIFICANCE AND IMPACT OF THE STUDY

Two strains of Lactobacillus isolated from human vagina of healthy premenopausal women could be promising candidates to be used in the preparation of probiotic products and for their use as health-promoting bacteria.

Increase of viability of entrapped cells of Lactobacillus delbrueckii ssp. bulgaricus in artificial sesame oil emulsions

A technique was developed to protect lactic acid bacteria (Lactobacillus delbrueckii ssp. bulgaricus) against simulated gastrointestinal conditions by encapsulation of bacterial cells within artificial sesame oil emulsions. Purified sesame oil bodies consisting of approximately 99% oil, 0.5% phospholipid, and 0.5% protein were decomposed by heating at 70 degrees C for 1 h. The bacteria cultured in nonfat milk were encapsulated in artificial oil emulsions constituted with decomposed sesame oil bodies and excess sesame or vegetable cooking oil. Viability of bacteria in storage at 4 degrees C for 16 d was substantially elevated from 0.023 to 5.45% after encapsulation. Compared with free cells, the entrapped bacteria demonstrated a significant increase (approximately 10(4) times) in survival rate when subjected to simulated high acid gastric or bile salt conditions. The results indicate that artificial sesame oil emulsion may serve as an effective biocapsule for encapsulation of bacteria in dairy products.

Survival of lactic acid bacteria in simulated gastrointestinal juice protected by a DNA-based complex gel

Salmon milt DNA was utilized in the approach to protect functional materials, proteins, microorganisms, drugs, etc., by forming a DNA-based complex gel with gelatin and kappa-carrageenan. The multiplier effect of the combination of DNA, gelatin and kappa-carrageenan was examined by measuring the release of methyl orange from the gel after being incubated in simulated gastric juice. The results indicated that the hydrogel made of DNA, gelatin and kappa-carrageenan can efficiently maintain the functional materials. Furthermore, a complex gel was developed and optimized by applying an emulsion of lactic acid bacteria and cacao oil onto the already prepared hydrogel. The existence of the lactic acid bacteria in the oil emulsion particles was confirmed by scanning electron microscopy. The protection capabilities in the simulated gastrointestinal juice, which had a viability of 1.50 x 10(6) CFU/g gel after 2 h incubation in the simulated gastric juice and 2.53 x 10(7) CFU/g gel after 6 h continued incubation in the simulated intestinal juice, were measured, in contrast to 2.58 x 10(7) CPU/g in the original gel before treatment.

Dietary influence of kefir on microbial activities in the mouse bowel

AIMS

In this work the microflora present in kefir, a fermented milk product, was studied together with the effect of kefir administration on different groups of indigenous bacteria of mouse bowel.

METHODS AND RESULTS

Kefir microflora was composed of lactic acid bacteria, acetic acid bacteria and yeasts. Yeast population was composed of Saccharomyces cerevisiae, S. unisporus, Candida kefir, Kluyveromyces marxianus and K. lactis. The streptococci levels in kefir treated mice increased by 10-fold and the levels of sulfite-reducing clostridia decreased by 100-fold. The number of lactic acid bacteria increased significantly.

CONCLUSIONS

The administration of kefir significantly increased the lactic acid bacteria counts in the mucosa of the bowel. Ingestion of kefir specifically lowered microbial populations of Enterobacteriaceae and clostridia.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first long-term study about the effects of the kefir administration on the intestinal microflora of mice.

Application of cereals and cereal components in functional foods: a review

The food industry is directing new product development towards the area of functional foods and functional food ingredients due to consumers' demand for healthier foods. In this respect, probiotic dairy foods containing human-derived Lactobacillus and Bifidobacterium species and prebiotic food formulations containing ingredients that cannot be digested by the human host in the upper gastrointestinal tract and can selectively stimulate the growth of one or a limited number of colonic bacteria have been recently introduced into the market. The aim of these products is to affect beneficially the gut microbial composition and activities. Cereals offer another alternative for the production of functional foods. The multiple beneficial effects of cereals can be exploited in different ways leading to the design of novel cereal foods or cereal ingredients that can target specific populations. Cereals can be used as fermentable substrates for the growth of probiotic microorganisms. The main parameters that have to be considered are the composition and processing of the cereal grains, the substrate formulation, the growth capability and productivity of the starter culture, the stability of the probiotic strain during storage, the organoleptic properties and the nutritional value of the final product. Additionally, cereals can be used as sources of nondigestible carbohydrates that besides promoting several beneficial physiological effects can also selectively stimulate the growth of lactobacilli and bifidobacteria present in the colon and act as prebiotics. Cereals contain water-soluble fibre, such as beta-glucan and arabinoxylan, oilgosaccharides, such as galacto- and fructo-oligosaccharides and resistant starch, which have been suggested to fulfil the prebiotic concept. Separation of specific fractions of fibre from different cereal varieties or cereal by-products, according to the knowledge of fibre distribution in cereal grains, could be achieved through processing technologies, such as milling, sieving, and debranning or pearling. Finally, cereal constituents, such as starch, can be used as encapsulation materials for probiotics in order to improve their stability during storage and enhance their viability during their passage through the adverse conditions of the gastrointestinal tract. It could be concluded that functional foods based on cereals is a challenging perspective, however, the development of new technologies of cereal processing that enhance their health potential and the acceptability of the food product are of primary importance.

Effect of pH and Dose on the Growth of Gut Bacteria on Prebiotic Carbohydrates in vitro

The effect of pH and substrate dose on the fermentation profile of a number of commercial prebiotics was analysed in triplicate using stirred, pH and temperature controlled anaerobic batch culture fermentations, inoculated with a fresh faecal slurry from one of three healthy volunteers. Bacterial numbers were enumerated using fluorescence in situ hybridisation. The commercial prebiotics investigated were fructooligosaccharides (FOS), inulin, galactooligosaccharides (GOS), isomaltooligosaccharides (IMO) and lactulose. Two pH values were investigated, i.e. pH 6 and 6.8. Doses of 1% and 2% (w/v) were investigated, equivalent to approximately 4 and 8 g per day, respectively, in an adult diet. It was found that both pH and dose altered the bacterial composition. It was observed that FOS and inulin demonstrated the greatest bifidogenic effect at pH 6.8 and 1% (w/v) carbohydrate, whereas GOS, IMO and lactulose demonstrated their greatest bifidogenic effect at pH 6 and 2% (w/v) carbohydrate. From this we can conclude that various prebiotics demonstrate differing bifidogenic effects at different conditions in vitro.

Probiotics--role in inflammatory bowel disease

The aetiology of inflammatory bowel disease is still unclean. Whilst a specific pathogen agent associated with these diseases has not been found, the rationale for probiotic therapy in inflammatory bowel disease is based on convincing evidence involving intestinal bacteria in their pathogenesis. Encouraging results have been obtained with probiotic therapy in several animal models of experimental colitis. The administration of highly concentrated probiotic preparations represents a valid approach both for the prevention of pouchitis onset and relapses. The encouraging results obtained in ulcerative colitis and Crohn's disease need to be further assessed in large double-blind trials.

Safety and efficacy of probiotic lactobacilli in promoting growth in post-weaning Swiss mice

Lactobacillus rhamnosus MA27/6B and L. acidophilus MA27/6R are strains used in feed as probiotics. Their safety profiles and growth-stimulating properties were investigated via in vivo studies on young Swiss mice. After repeated administrations of different probiotic preparations in drinking water, safety parameters determined from liver, spleen and total weight remained unchanged. The growth-stimulating properties of viable or dead lactobacilli were studied after supplementation in drinking water. The feed intake (FI), water intake and body weight gain (WG) of the animals were compared to those of control mice. The lactobacilli supplementation of a sub-optimal diet made of barley allow recording of measurable growth performance of mice. It significantly increased WG compared to control groups (P < 0.01), by +28.9% and +31.7% for L. rhamnosus MA27/6B and L. acidophilus MA27/6R, respectively. This WG was correlated with a decrease in the consumption index. The effect of the dose ingested was also investigated: 10(8) lactobacilli CFU/mouse/day produced greater WG than 10(2), 10(4) or 10(6) CFU/mouse/day. No significant differences in growth performance parameters were observed between mice fed with 10(8) cells of viable or nonviable preparations. The mouse assay described could be used as a preliminary criterion when screening candidate probiotics for growth performance properties.

Immune responses in rhesus rotavirus-challenged BALB/c mice treated with bifidobacteria and prebiotic supplements

Bifidobacterium species (B. bifidum and B. infantis), with or without prebiotic compounds (arabino-galactan, short-chain fructo-oligosaccharide, iso-malto-dextrins), were orally fed to Balb/c pups (n = 192) to evaluate their potential synergistic effects on modulating the course of rhesus rotavirus (RRV) infection, as well as their ability to mediate the associated mucosal and humoral immune responses. Rotavirus-specific IgA and IgG in serum, rotavirus antigen, and specific IgA in feces were measured by ELISA. Mucosal total IgA and IgG levels were determined in Peyer's patches by flow cytometry. Significantly delayed onset (p = 0.001) and early resolution (p < 0.001) of diarrhea were observed in bifidobacteria-treated, RRV-infected mice compared with RRV-infected control mice. Supplementation with prebiotic compounds did not shorten the clinical diarrhea course more than that observed with bifidobacteria treatment alone. Rotavirus-specific IgA in feces was 16-fold elevated on d 5 postinfection in bifidobacteria-treated, RRV-infected mice compared with the RRV-infected alone group. In addition, the level of rotavirus-specific IgA in serum was four-fold higher in bifidobacteria-treated, RRV-infected litters versus mice challenged with RRV alone on 28 and 42 d postinfection. No enhancement of the immune response was found in RRV-infected mice that were treated with both bifidobacteria and prebiotic compounds over those treated with bifidobacteria only. The findings suggest that bifidobacteria may act as an adjuvant by modulating early mucosal and strong humoral rotavirus-specific immune responses, and mitigate severity of rotavirus-induced diarrhea.

Impact on human intestinal microflora of an Enterococcus faecium probiotic and vancomycin

The aims of this study were to evaluate the impact of a fermented milk product containing viable Enterococcus faecium on human intestinal microflora and to evaluate any risk of development of vancomycin-resistant enterococci (VRE). Twenty Danish and 20 Swedish healthy volunteers were given 150 ml of the fermented milk product once daily, equivalent to a daily dose of 4.5 x 10(9) to 7.5 x 10(9) CFU E. faecium, for 10 d. Half of the volunteers also received 125 mg vancomycin orally q.i.d. for 10 d. Faecal samples were collected on day 0 before intake, on day 10 directly after end of intake and on day 31, 3 weeks after the end of the experiment. There was a significant increase in the total number of enterococci on day 10 (p < 0.01) in the group receiving only the E. faecium supplement, but 3 weeks later the level was as before intake. In the vancomycin group, the total number of enterococci was reduced on day 10 (p < 0.01) but had increased on day 31 (p < 0.01) in relation to day 0. In none of the Swedish and 4 of the Danish volunteers, VRE were sporadically detected, but without relation to intake of the probiotic or vancomycin. In healthy young Danish individuals the VRE carrier rate tended to be higher than previously found.

Chemopreventive effect of Lactobacillus rhamnosus on growth of a subcutaneously implanted bladder cancer cell line in the mouse

Lactic acid bacteria are known to have beneficial effects on the host, such as preventing carcinogenesis. The present study was designed to evaluate the chemopreventive effects of Lactobacillus rhamnosus strain GG (LGG) in suppressing bladder cancer formation in a murine subcutaneous model of bladder cancer involving the inoculation of MB49 cells in C57B / L6 mice. After tumor implantation, one group of mice (n = 8) was fed LGG immediately. The remaining mice that had tumors between 0.03 - 0.1 cm(3) were divided into two groups: those fed LGG after 7 days (n = 7) and those fed saline (n = 7). A second group of mice without any inoculation of MB49 cells was fed either LGG (n = 10) or saline (n = 10) and served as non-tumor-bearing controls. LGG was administered orally at 1.6 x 10(8) colony-forming units daily. Mice fed LGG immediately after tumor cell implantation formed smaller tumors and some did not develop tumors (2 out of 8 mice), when the tumor burden was small. The level of spleen CD3, CD4 and CD8a T lymphocytes, as well as natural killer cells in mice fed immediately with LGG was also higher than that in control tumor-bearing mice. There was an increase in lymphocytes and granulocytes in tumor sections, especially from the immediately fed group as compared to the controls. Our results suggest that oral consumption of LGG may prevent tumor growth via modulation of the immune system. The potential of LGG as an adjunct therapy in the treatment of bladder cancer could be further explored.

Application of RBGR--a simple way for screening of oxygen tolerance in probiotic bacteria

Oxygen toxicity is a major problem in the survival of probiotic bacteria in dairy foods. High levels of oxygen in the product are detrimental to the viability of these predominantly anaerobic bacteria. Screening probiotic bacteria for oxygen tolerance before their incorporation could ensure high cell counts in food products during storage. Reported techniques have focused only on qualitative estimations of oxygen tolerance in probiotic bacteria. To characterize the oxygen tolerance of a large number of organisms, a quantitative measurement is essential. For the first time, the oxygen tolerance of several probiotic strains was measured quantitatively using an index known as Relative Bacterial Growth Ratio (RBGR). The tolerance to oxygen varied between organisms, and this technique can therefore be applied for screening probiotic bacteria for oxygen tolerance.

Usefulness of epifluorescence for quantitative analysis of lactobacilli in probiotic feed

AIMS

Enumeration of total, active or viable probiotic micro-organisms from liquid or solid commercial feedstuffs was studied during processing and storage.

METHODS AND RESULTS

After sample preparation, an epifluorescence microscopy technique and a plating method were investigated comparatively. It was shown that (i) on the day of manufacture, active or viable bacteria were in equivalent amounts and that viable numbers then decreased, depending on the different processing and storage factors enhancing ABNC production, (ii) the amount of total and active lactobacilli remained close and quite stable for months at a high level (>10(8) active fluorescent units).

CONCLUSIONS

Processing and storage promoted ABNC cells in the products tested. Consequently, both techniques should be used to evaluate the viable-dead-active status of bacteria for which functional properties are claimed.

SIGNIFICANCE AND IMPACT OF THE STUDY

Enumeration of the whole probiotic bacterial population should be take into account for guidelines and labelling since non-viable bacteria could have a probiotic effect.

Effects of probiotic administration upon the composition and enzymatic activity of human fecal microbiota in patients with irritable bowel syndrome or functional diarrhea

In a clinical trial, 10 patients suffering from irritable bowel syndrome or functional diarrhea were administered the probiotic preparation VSL-3. Preliminary results indicated that administration of VSL-3 improved the clinical picture and changed the composition and biochemistry of fecal microbiota. Titer variations of intestinal bacterial groups were evaluated by culture and PCR techniques. A significant increase in lactobacilli, bifidobacteria and Streptococcus thermophilus was observed as a consequence of probiotic treatment, while enterococci, coliforms, Bacteroides and Clostridium perfringens did not change significantly. The strains Bifidobacterium infantis Y1 and Bifidobacterium breve Y8, included in VSL-3, were specifically detected in feces of patients treated with the probiotic by using strain-specific PCR primers. In addition, fecal beta-galactosidase increased and urease activities decreased as a result of changes in the intestinal microbiota induced by VSL-3 administration.

In vitro adherence properties of Lactobacillus rhamnosus DR20 and Bifidobacterium lactis DR10 strains and their antagonistic activity against an enterotoxigenic Escherichia coli

Adhesion and colonisation properties of three probiotic strains namely, Lactobacillus rhamnosus DR20, L. acidophilus HN017, and Bifidobacterium lactis DR10, were determined in vitro using the differentiated human intestinal cell-lines including HT-29, Caco-2, and HT29-MTX, and compared with properties of L. acidophilus LA-1 and L. rhamnosus GG (two commercial probiotic strains). Two independent methods were employed to quantitate the "adhesiveness" of each strain. In the first method, the bacteria adhered to human cells were detected by Gram staining and counted in different fields under a microscope. Bacteria were also radio-labelled and extent of adhesion determined by scintillation counting. All three strains showed strong adhesion with the human intestinal cell lines in vitro. Adhesion indices of the three strains to two cell lines, i.e. HT-29, and Caco-2 varied between 99 +/- 17 and 219 +/- 36. With mucus-secreting cell-line HT29-MTX, the adhesion indices of all the strains were 2-3 times higher. The adhesion indices of L. acidophilus LA-1 and L. rhamnosus GG were comparable to the other three probiotic strains. We also investigated the inhibitory effect of adhering strains against the intestinal cell monolayer colonization by a known enterotoxigenic strain of Escherichia coli (strain O157:H7). Pre-treatment of E. coli O157:H7 with 2.5-fold concentrated cell-free culture supernatants from L. acidophilus HN017, L. rhamnosus DR20 and B. lactis DR10 reduced the culturable E. coli numbers on TSB plates and also reduced the invasiveness and cell association characteristics of this toxic strain. The inhibitory molecules secreted into the spent media by these strains were partially affected by treatments with lactate dehydrogenase, trypsin and proteinase K suggesting that overall inhibition may be due to a synergistic action of lactic acid and proteinaceous substances.

Bile salt hydrolase activity and resistance to toxicity of conjugated bile salts are unrelated properties in lactobacilli

Bacteria of numerous species isolated from the human gastrointestinal tract express bile salt hydrolase (BSH) activity. How this activity contributes to functions of the microorganisms in the gastrointestinal tract is not known. We tested the hypothesis that a BSH protects the cells that produce it from the toxicity of conjugated bile salts. Forty-nine strains of numerous Lactobacillus spp. were assayed to determine their capacities to express BSH activities (taurodeoxycholic acid [TDCA] hydrolase and taurocholic acid [TCA] hydrolase activities) and their capacities to resist the toxicity of a conjugated bile acid (TDCA). Thirty of these strains had been isolated from the human intestine, 15 had been recovered from dairy products, and 4 had originated from other sources. Twenty-six of the strains expressed both TDCA hydrolase and TCA hydrolase activities. One strain that expressed TDCA hydrolase activity did not express TCA hydrolase activity. Conversely, in one strain for which the assay for TDCA hydrolase activity gave a negative result there was evidence of TCA hydrolase activity. Twenty-five of the strains were found to resist the toxicity of TDCA. Fourteen of these strains were of human origin, nine were from dairy products, and two were from other sources. Of the 26 strains expressing both TDCA hydrolase and TCA hydrolase activities, 15 were resistant to TDCA toxicity, 6 were susceptible, and 5 gave inconclusive results. Of the 17 strains that gave negative results for either of the enzymes, 7 were resistant to the toxicity, 9 were susceptible, and 1 gave inconclusive results. These findings do not support the hypothesis tested. They suggest, however, that BSH activity is important at some level for lactobacillus colonization of the human intestine.

Probiotics and antibiotics in inflammatory bowel disease

Many experimental and clinical observations suggest a potential role for intestinal microflora in the pathogenesis of inflammatory bowel disease. Manipulation of the luminal content using antibiotics and/or probiotics may represent a potentially effective therapeutic option. Results of antibiotic treatment in inflammatory bowel disease are controversial, but this approach is frequently and successfully adopted in clinical practice. Recent data support the potential therapeutic role of probiotics in inflammatory bowel disease. In particular, a highly concentrated probiotic preparation was shown to be superior to placebo both on the prevention of pouchitis onset and of chronic pouchitis relapse. Its role in the maintenance treatment of ulcerative colitis and Crohn disease needs to be further assessed by large, double-blind, controlled trials. Future research needs to be focused on obtaining more precise information on the enteric microflora and the mechanisms of action of probiotics.

Intra- and extracellular beta-galactosidases from Bifidobacterium bifidum and B. infantis: molecular cloning, heterologous expression, and comparative characterization

Three beta-galactosidase genes from Bifidobacterium bifidum DSM20215 and one beta-galactosidase gene from Bifidobacterium infantis DSM20088 were isolated and characterized. The three B. bifidum beta-galactosidases exhibited a low degree of amino acid sequence similarity to each other and to previously published beta-galactosidases classified as family 2 glycosyl hydrolases. Likewise, the B. infantis beta-galactosidase was distantly related to enzymes classified as family 42 glycosyl hydrolases. One of the enzymes from B. bifidum, termed BIF3, is most probably an extracellular enzyme, since it contained a signal sequence which was cleaved off during heterologous expression of the enzyme in Escherichia coli. Other exceptional features of the BIF3 beta-galactosidase were (i) the monomeric structure of the active enzyme, comprising 1,752 amino acid residues (188 kDa) and (ii) the molecular organization into an N-terminal beta-galactosidase domain and a C-terminal galactose binding domain. The other two B. bifidum beta-galactosidases and the enzyme from B. infantis were multimeric, intracellular enzymes with molecular masses similar to typical family 2 and family 42 glycosyl hydrolases, respectively. Despite the differences in size, molecular composition, and amino acid sequence, all four beta-galactosidases were highly specific for hydrolysis of beta-D-galactosidic linkages, and all four enzymes were able to transgalactosylate with lactose as a substrate.

Quality assurance criteria for probiotic bacteria

Acid and bile stability and intestinal mucosal adhesion properties are among the criteria used to select probiotic microbes. The quality control of probiotic cultures in foods traditionally has relied solely on tests to ensure that an adequate number of viable bacteria are present in the products throughout their shelf lives. Viability is an important factor, but not the only criterion for quality assurance. To be effective, probiotic strains must retain the functional health characteristics for which they were originally selected. Such characteristics include the ability to survive transit through the stomach and small intestine and to colonize the human gastrointestinal tract. In vitro test protocols can be readily adopted to examine the maintenance of a strain's ability to tolerate acidic conditions, survive and grow in the presence of bile, and metabolize selective substrates. Molecular techniques are also available to examine strain stability. Adhesion characterization may be an important quality-control method for assessing gut barrier effects. Adhesion has been related to shortening the duration of diarrhea, immunogenic effects, competitive exclusion, and other health effects. Adhesion properties should be carefully monitored, including adhesion to intestinal cells (eg, Caco-2) and human intestinal mucus. This article outlines the types of in vitro testing that can be used to ensure quality control of functional probiotic strains.

Probiotic bacteria in fermented foods: product characteristics and starter organisms

Probiotic bacteria are sold mainly in fermented foods, and dairy products play a predominant role as carriers of probiotics. These foods are well suited to promoting the positive health image of probiotics for several reasons: 1) fermented foods, and dairy products in particular, already have a positive health image; 2) consumers are familiar with the fact that fermented foods contain living microorganisms (bacteria); and 3) probiotics used as starter organisms combine the positive images of fermentation and probiotic cultures. When probiotics are added to fermented foods, several factors must be considered that may influence the ability of the probiotics to survive in the product and become active when entering the consumer's gastrointestinal tract. These factors include 1) the physiologic state of the probiotic organisms added (whether the cells are from the logarithmic or the stationary growth phase), 2) the physical conditions of product storage (eg, temperature), 3) the chemical composition of the product to which the probiotics are added (eg, acidity, available carbohydrate content, nitrogen sources, mineral content, water activity, and oxygen content), and 4) possible interactions of the probiotics with the starter cultures (eg, bacteriocin production, antagonism, and synergism). The interactions of probiotics with either the food matrix or the starter culture may be even more intensive when probiotics are used as a component of the starter culture. Some of these aspects are discussed in this article, with an emphasis on dairy products such as milk, yogurt, and cheese.

In vitro selection criteria for probiotic bacteria of human origin: correlation with in vivo findings

The enteric flora comprises approximately 95% of the total number of cells in the human body and can elicit immune responses while protecting against microbial pathogens. However, the resident bacterial flora of the gastrointestinal tract may also be implicated in the pathogenesis of diseases such as inflammatory bowel disease (ulcerative colitis and Crohn disease). The objectives of the Probiotic Research Group based at University College Cork were to isolate and identify lactic acid bacteria exhibiting beneficial probiotic traits, such as bile tolerance in the absence of deconjugation activity, acid resistance, adherence to host epithelial tissue, and in vitro antagonism of pathogenic microorganisms or those suspected of promoting inflammation. To isolate potentially effective probiotic bacteria, we screened the microbial population adhering to surgically resected segments of the gastrointestinal tract (the environment in which they may subsequently be reintroduced and required to function). In total, 1500 bacterial strains from resected human terminal ilea were assessed. From among these organisms, Lactobacillus salivarius subsp. salivarius strain UCC118 was selected for further study. In mouse feeding trials, milk-borne L. salivarius strain UCC118 could successfully colonize the murine gastrointestinal tract. A human feeding study conducted in 80 healthy volunteers showed that yogurt can be used as a vehicle for delivery of strain UCC118 to the human gastrointestinal tract with considerable efficacy in influencing gut flora and colonization. In summary, we developed criteria for in vitro selection of probiotic bacteria that may reflect certain in vivo effects on the host such as modulation of gastrointestinal tract microflora.

Market potential for probiotics

"Functional foods" as a marketing term was initiated in Japan in the late 1980s and is used to describe foods fortified with ingredients capable of producing health benefits. This concept is becoming increasingly popular with consumers because of a heightened awareness of the link between health, nutrition, and diet. Food manufacturers are enthusiastic about developing such products because the added ingredients give increased value to food. The global market for functional foods in the coming years is predicted to grow rapidly. Although Japan currently accounts for about one-half of this market, the fastest rate of growth is expected to be in the United States. Probiotic products represent a strong growth area within the functional foods group and intense research efforts are under way to develop dairy products into which probiotic organisms such as Lactobacillus and Bifidobacterium species are incorporated. Such probiotic foods may modulate gut microbial composition, thereby leading to improved gut health, for example, through improved tolerance to lactose in lactose-intolerant individuals or improved resistance to pathogenic bacteria. Large numbers of viable microorganisms are likely to be required in the food product, which should be consumed regularly to experience the health effect. The probiotic market, especially dairy products such as yogurts and fermented milks, has experienced rapid growth in Europe. The long-term exploitation of probiotics as health promoters is dependent on several factors, including sound, scientifically proven clinical evidence of health-promoting activity; accurate consumer information; effective marketing strategies; and, above all, a quality product that fulfills consumer expectations.

Direct in situ viability assessment of bacteria in probiotic dairy products using viability staining in conjunction with confocal scanning laser microscopy

The viability of the human probiotic strains Lactobacillus paracasei NFBC 338 and Bifidobacterium sp. strain UCC 35612 in reconstituted skim milk was assessed by confocal scanning laser microscopy using the LIVE/DEAD BacLight viability stain. The technique was rapid (<30 min) and clearly differentiated live from heat-killed bacteria. The microscopic enumeration of various proportions of viable to heat-killed bacteria was then compared with conventional plating on nutrient agar. Direct microscopic enumeration of bacteria indicated that plate counting led to an underestimation of bacterial numbers, which was most likely related to clumping. Similarly, LIVE/DEAD BacLight staining yielded bacterial counts that were higher than cell numbers obtained by plate counting (CFU) in milk and fermented milk. These results indicate the value of the microscopic approach for rapid viability testing of such probiotic products. In contrast, the numbers obtained by direct microscopic counting for Cheddar cheese and spray-dried probiotic milk powder were lower than those obtained by plate counting. These results highlight the limitations of LIVE/DEAD BacLight staining and the need to optimize the technique for different strain-product combinations. The minimum detection limit for in situ viability staining in conjunction with confocal scanning laser microscopy enumeration was approximately 10(8) bacteria/ml (equivalent to approximately 10(7) CFU/ml), based on Bifidobacterium sp. strain UCC 35612 counts in maximum-recovery diluent.

Probiotic bacteria: safety, functional and technological properties

During the past two decades probiotic (health promoting) micro-organisms have been increasingly included in various types of food products, especially in fermented milks. Several aspects, including safety, functional and technological characteristics, have to be taken into consideration in the selection process of probiotic micro-organisms. Safety aspects include specifications such as origin (healthy human GI-tract), non-pathogenicity and antibiotic resistance characteristics. Functional aspects include viability and persistence in the GI-tract, immunomodulation, antagonistic and antimutagenic properties. Before probiotic strains, chosen on the basis of their good safety and functional characteristics, can benefit the consumer, they must first be able to be manufactured under industrial conditions. Furthermore, they have to survive and retain their functionality during storage, and also in the foods into which they are incorporated without producing off-flavours. Factors related to the technological and sensory aspects of probiotic food production are of utmost importance since only by satisfying the demands of the consumer can the food industry succeed in promoting the consumption of functional probiotic products in the future.

Lactobacillus johnsonii La1 shares carbohydrate-binding specificities with several enteropathogenic bacteria

The carbohydrate-binding specificities of the probiotic lactic acid bacterium Lactobacillus johnsonii La1 (a health-beneficial bacterial strain able to be incorporated into the human intestinal microflora) were investigated in vitro. First various soluble complex carbohydrates were tested as potential inhibitors of the strain adhesion onto Caco-2 intestinal epithelial cells, and then bacterial binding to glycolipids immobilized on TLC plates was probed. Two major carbohydrate-binding specificities of Lactobacillus johnsonii La1 were identified. A first one for an Endo-H treated yeast cell wall mannoprotein carrying mainly O:-linked oligomannosides, and a second one for the gangliotri- and gangliotetra-osylceramides (asialo-GM1). Similar carbohydrate-binding specificities are known to be expressed on cell surface adhesins of several enteropathogens, enabling them to adhere to the host gut mucosa. These findings corroborate the hypothesis that selected probiotic bacterial strains could be able to compete with enteropathogens for the same carbohydrate receptors in the gut.

Specific detection of bifidobacterium strains in a pharmaceutical probiotic product and in human feces by polymerase chain reaction

For PCR specific detection of the strains Bifidobacterium longum Y 10, B. infantis Y 1 and B. breve Y 8 used in a new probiotic product (VSL-3), strains-specific rDNA primers have been developed. Spacer regions between the 16S and 23S rRNA genes (ITS) of the three strains were amplified by PCR with conserved primers and the nucleotide sequence of these ITSs were determined. On the basis of their comparison with the rDNA sequences retrieved from GenBank, we designed new primers which specifically recognize the species B. breve and the two strains B. infantis Y 1 and B. breve Y 8. Specificity of these primers was confirmed through the analysis of 60 bifidobacteria strains belonging to the more representative human species. The feasibility of this PCR method was investigated in commercial VSL-3 product and fecal samples collected from 4 patients affected by inflammatory bowel deseases and two healthy subjects before and after the VSL-3 administration. By PCR analysis of different VSL-3 commercial batches we were successful in differentiating and quantifying the strains B. longum Y 10, B. infantis Y 1 and B. breve Y 8. B. infantis Y 1 and B. breve Y 8 could be detected at high concentration in fecal specimens of both patients and subjects treated with the probiotic preparation, showing a different colonization behaviour. Seven days after the VSL-3 treatment suspension, no patients and subjects harbored B. infantis Y 1 and B. breve Y 8, indicating a transient presence of these exogenous strains.

Quantitative approach in the study of adhesion of lactic acid bacteria to intestinal cells and their competition with enterobacteria

To describe the phenomena of bacterial adhesion to intestinal cells and the competition for adhesion between bacteria, mathematical equations based on a simple dissociation process involving a finite number of bacterial receptors on intestinal cell surface were developed. The equations allow the estimation of the maximum number of Lactobacillus sp. and Escherichia coli cells that can adhere to Caco-2 cells and intestinal mucus; they also characterize the affinity of the bacteria to Caco-2 cells and intestinal and fecal mucus and the theoretical adhesion ratio of two bacteria present in a mixed suspension. The competition for adhesion between Lactobacillus rhamnosus GG and E. coli TG1 appeared to follow the proposed kinetics, whereas the competition between Lactobacillus casei Shirota and E. coli TG1 may involve multiple adhesion sites or a soluble factor in the culture medium of the former. The displacement of the adhered Lactobacillus by E. coli TG1 seemed to be a rapid process, whereas the displacement of E. coli TG1 by the Lactobacillus took more than an hour.