Strains Of Probiotic Bacteria Research Articles

Growth and metabolism of selected strains of probiotic bacteria in milk- and water-based cereal puddings

Abstract The growth and metabolism of four probiotic strains ( Lactobacillus acidophilus La5 and 1748, Bifidobacterium animalis Bb12, and Lactobacillus rhamnosus GG) were studied in milk- and water-based puddings containing both maize and rice flour. All pudding-formulations were produced both with and without the potential prebiotic polydextrose, Litesse™, to see if this addition had any effect on the growth, metabolism and survival of the probiotic strains. Puddings were analysed for viable cell count, pH and metabolites during fermentation (12 h, 37°C) and after refrigerated storage (21 d, 4–6°C). All strains showed good growth and survival in milk-based puddings (8–9.1 log cfu g −1 ), but L. rhamnosus GG was the only strain with an acceptable survival in water-based puddings (8 log cfu g −1 ). After storage, 560–9800 mg kg −1 lactic acid was produced, with significantly higher concentrations in milk-based puddings ( p L. rhamnosus GG, reaching 18 mg kg −1 in milk-based puddings. In most cases, puddings prepared with or without the addition of Litesse™ were not significantly different.

Growth and metabolism of selected strains of probiotic bacteria, in maize porridge with added malted barley

A fermented probiotic maize porridge with high energy density and low viscosity was prepared, using maize flour and barley malt. The porridge was fermented with four probiotic strains (grown separately): Lactobacillus reuteri, Lb. acidophilus (LA5 and 1748) and Lb. rhamnosus GG. These strains were inoculated at two levels; to obtain approx. 7 or 6 log cfu g −1 in the porridge at 0 h. The porridge was fermented for 24 h at 37 °C, and analysed for viable cell count, pH, organic acids, volatile aromatic compounds and sugar content. The inoculated cell concentration was shown to be particularly important during the first hours of the fermentation period, showing a delayed production of most metabolites in porridge inoculated with approx. 6 log cfu g −1. Most strains reached maximum cell count after 12-h fermentation (7.2–8.2 log cfu g −1), with a pH below 4.0. Depending on the strain, lactic acid was produced in amounts ranging from 1360 to 4000 mg kg −1. Lb. reuteri metabolised succinate, while pyruvate and small amounts of diacetyl were detected in porridge inoculated with Lb. acidophilus LA5 and Lb. acidophilus 1748. High amounts of diacetyl (6 mg kg −1) and acetoin (27 mg kg −1) were detected in porridge inoculated with Lb. rhamnosus GG. Porridge inoculated with Lb. acidophilus LA5 and Lb. acidophilus 1748, contained acetaldehyde, while both Lb. reuteri and Lb. rhamnosus GG reduced the acetaldehyde to ethanol. Lb. reuteri utilised both maltose and glucose as carbohydrate sources, while Lb. acidophilus LA5, Lb. acidophilus 1748 and Lb. rhamnosus GG utilised only glucose.

Long-term consumption of infant formulas containing live probiotic bacteria: tolerance and safety

Nonpathogenic live bacteria are consumed as food by many children, particularly in the form of yogurt. The tolerance and safety of long-term consumption of specific types and strains of probiotic bacteria are not well documented. The goal was to evaluate tolerance to formulas containing 2 levels of probiotic supplementation and effects on growth, general clinical status, and intestinal health in free-living healthy infants. This was a prospective, double-blind, randomized, placebo-controlled study of healthy infants aged 3-24 mo. Infants were assigned to receive a standard milk-based formula containing 1 x 10(7) colony-forming units (CFU)/g each of Bifidobacterium lactis and Streptococcus thermophilus, formula containing 1 x 10(6) CFU/g each of B. lactis and S. thermophilus, or unsupplemented formula. Clinical outcomes included formula intake, gastrointestinal tolerance, anthropometric measures, daycare attendance, and history of illness. One hundred eighteen infants aged ( +/- SD) 7.0 +/- 2.9 mo at enrollment consumed formula for 210 +/- 127 d. There were no significant differences in age, sex, formula consumption, or length of study between groups. The supplemented formulas were well accepted and were associated with a lower frequency of reported colic or irritability (P < 0.001) and a lower frequency of antibiotic use (P < 0.001) than was the unsupplemented formula. There were no significant differences between groups in growth, health care attention seeking, daycare absenteeism, or other health variables. Long-term consumption of formulas supplemented with B. lactis and S. thermophilus was well tolerated and safe and resulted in adequate growth, reduced reporting of colic or irritability, and a lower frequency of antibiotic use.

Probiotic cell counts and acidification in fermented milks supplemented with milk protein hydrolysates

Abstract In the present work, the effect of milk protein hydrolysates on probiotic cell counts and acidification in fermented milks was studied. Two strains of probiotic bacteria, Lactobacillus acidophilus LA-5 and Lactobacillus rhamnosus LR-35, were used in mixed culture with Streptococcus thermophilus ST-7. The effect of three casein hydrolysates and three whey protein hydrolysates were investigated by adding them to milk at a concentration ranging from 0.25 to 4 g L −1 . Addition of hydrolysate enhanced the growth of S. thermophilus and acidification, thus reducing the fermentation time, and growth of probiotic bacteria. On the other hand, survival of probiotic bacteria was improved when milk was added with hydrolysate. As a consequence, the addition of hydrolysate had a differential action on probiotic cell counts in fermented milks after storage, depending on the balance between its negative effect on growth of probiotic bacteria and its positive effect on the survival of probiotic bacteria.

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 °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.

Influences of probiotic bacteria on organic acid production by pig caecal bacteria in vitro.

The mechanism of action of probiotics is largely unknown. A potential mechanism should be to increase the production of short-chain fatty acids (SCFA), known modulators of gut functions, by the bacterial ecosystem in the large intestine. The present paper reviews our recent studies in which the capacity of probiotic bacteria to increase the production of SCFA by pig caecal bacteria was investigated using batch-culture and continuous-culture techniques. All four commercial probiotic preparations and three strains of probiotic bacteria dose-dependently accelerated the net production of SCFA, succinic acid and lactic acid without changing the acid profile, and slowed the net production of NH4. Effects on organic acid production did not vary among different probiotic species. Neither probiotic preparations nor probiotic bacteria affected the organic acid production from glucose, gastric mucin, starch or lactose, or organic acids produced:added saccharide. Glucose abolished these effects of probiotic preparations. However, the capacity of probiotics to increase SCFA production was not modified by gastric mucin, starch or lactose. These results indicate that probiotic bacteria increase SCFA production by accelerating the breakdown of carbohydrates that are resistant to indigenous bacteria, and suggest that the concept of prebiotics in terms of SCFA production as a measure of probiotic function is arguable.

Effects of micronization on viability and thermotolerance of probiotic freeze-dried cultures

Abstract Three strains of probiotic freeze-dried bacteria, Bifidobacterium breve R070 (BB R070), Bifidobacterium longum R023 (BL R023), and Lactobacillus acidophilus R335 (LA R335), were micronized using a spiral jet mill as grinding system, in order to decrease the powder particle size for incorporation in multiphase low-diameter microcapsules produced by emulsification and spray-drying. The effects of grind air pressure (1, 2, 4 or 5.5 bar) and product feed rate (150 or 300 g h −1 ) on powder particle-size distribution and bacterial viability were evaluated. The D ( ν , 0.9) of the micronized powder was found to be only affected by grind air pressure ( P −1 was selected as the least destructive treatment (survival rate of 25.5±5.2%) to produce powders of probiotic freeze-dried cultures with particle-size distribution suitable for the microencapsulation technology ( D ( ν , 0.9) E a , D 45°C , D 65°C , D 80°C ). Results indicated that BL R023 displayed intrinsic low heat resistance whereas particle-size reduction dramatically increased the thermosensitivity of BB R070. Micronization is an effective way of reducing powder particle size of freeze-dried bacterial cultures for subsequent use in cell immobilization applications with low heat treatment.

Lactic acid starter and probiotic bacteria: a comparative “in vitro” study of probiotic characteristics and biological barrier resistance

Probiotic characteristics (deconjugation of bile salts, hydrophobicity and β-galactosidase activity) and the resistance to biological barriers (gastric juice and bile salts) of 24 strains of lactic acid starter bacteria ( Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and Lactococcus lactis) and 24 strains of probiotic bacteria ( Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus and bifidobacteria) were compared. Among the probiotic bacteria tested, Lactobacillus acidophilus was the most interesting species since it showed high values of resistance to gastric juice and bile, hydrophobicity and β-galactosidase and bile salts deconjugation activities. Bifidobacterium bifidum strains showed the same behavior, although the values of the parameters investigated were slightly lower than those obtained for Lactobacillus acidophilus. On the other hand, it was demonstrated that Lactobacillus delbrueckii subsp. bulgaricus was the lactic acid starter species with the best probiotic characteristics among the starter species assessed. It was resistant to gastric juice and bile, and showed high values for β-galactosidase activity. On the other hand, lactic acid starter bacteria showed hydrophobicity values similar to or higher than those obtained for the strains of the Lactobacillus casei . According to the results found, the total probiotic value of a fermented dairy product should take into account not only the intestinal probiotic cultures used in the formulation but also the probiotic contribution of the lactic acid starter microflora.

Effect of Milk Base and Starter Culture on Acidification, Texture, and Probiotic Cell Counts in Fermented Milk Processing

In the present work, the compared effect of milk base and starter culture on acidification, texture, growth, and stability of probiotic bacteria in fermented milk processing, was studied. Two strains of probiotic bacteria were used, Lactobacillus acidophilus LA5 and L. rhamnosus LR35, with two starter cultures. One starter culture consisted only of Streptococcus thermophilus ST7 (single starter culture); the other was a yogurt mixed culture with S. thermophilus ST7 and L. bulgaricus LB12 (mixed starter culture). For the milk base preparation, four commercial dairy ingredients were tested (two milk protein concentrates and two casein hydrolysates). The resulting fermented milks were compared to those obtained with control milk (without enrichment) and milk added with skim milk powder. The performance of the two probiotic strains were opposite. L. acidophilus LA5 grew well on milk but showed a poor stability during storage. L. rhamnosus LR35 grew weakly on milk but was remarkably stable during storage. With the strains tested in this study, the use of the single starter culture and the addition of casein hydrolysate gave the best probiotic cell counts. The fermentation time was of about 11h, and the probiotic level after five weeks of storage was greater than 106 cfu/ml for L. acidophilus LA5 and 107 cfu/ml for L. rhamnosus LR35. However, an optimization of the level of casein hydrolysate added to milk base has to be done, in order to improve texture and flavor when using this dairy ingredient.

Probiotics in prevention of antibiotic associated diarrhoea: meta-analysis

Objective: To evaluate efficacy of probiotics in prevention and treatment of diarrhoea associated with the use of antibiotics.Design: Meta-analysis; outcome data (proportion of patients not getting diarrhoea) were analysed, pooled,...

Influence of compounds associated with fermented dairy products on the growth of lactic acid starter and probiotic bacteria

Abstract The growth of 24 strains of lactic acid starter bacteria ( Streptococcus thermophilus , Lactobacillus delbrueckii subsp. bulgaricus and Lactococcus lactis ) and 24 strains of probiotic bacteria ( Lactobacillus acidophilus , Lactobacillus casei , Lactobacillus paracasei , Lactobacillus rhamnosus and bifidobacteria) in liquid media containing different substances was assessed. The substances used were salts (NaCl and KCl); sugars (sucrose and lactose); sweeteners (acesulfame and aspartame); aroma compounds (diacetyl, acetaldehyde and acetoin); natural colorings for fermented milk (red, yellow and orange colorings); flavoring agents (strawberry, vanilla, peach and banana essences); flavoring–coloring agents (strawberry, vanilla and peach); nisin, natamycin and lysozyme. Bacterial growth in the presence of natural fruit juices (green apple, kiwi, pineapple, peach and strawberry) with or without neutralization and cell viability in lactic acid acidified (pH 4 and 5) milk for 4 weeks at 5°C were also studied. Some compounds (KCl, sweeteners, aroma compounds, natamycin, flavoring agents and the peach flavoring–coloring agent) did not influence the growth of the strains in the concentrations commonly used in the dairy industry. The effect of other substances (especially flavoring–coloring agents) on the growth of lactic acid starters and probiotic bacteria was strain-dependent. Natural fruit juices weakly inhibited mainly S. thermophilus strains. Cell viability during cold storage in acidified milk was satisfactory for L. delbrueckii subsp. bulgaricus and L. casei group strains. For L. acidophilus and Bifidobacterium , the decreases in cell counts at pH 5 were negligible. Nevertheless, decreases from 1.6 to 6.2 and from 0.1 to 7.6 log orders, respectively were observed at pH 4.

Role of Lactic Acid Bacteria (LAB) in Food Preservation and Human Health – A Review

Fermentation of various food stuffs by lactic acid bacteria (LAB) is one of the oldest forms of biopreservation practiced by mankind . Bacterial antagonism has been recognized for over a century but in recent years this phenomenon has received more scientific attention , particularly in the use of various strains of lactic acid bacteria One important attribute of many LAB is their ability to produce antimicrobial compounds called bacteriocins. In recent years interest in these compounds has grown substantially due to their potential usefulness as natural substitute for chemical food preservatives in the production of foods with enhanced shelf life and / or safety. There is growing consumer awareness of the link between diet and health. Recent scientific evidence supports the role of probiotic LAB in mediating many positive health effects.Traditional probiotic dairy strains of lactic acid bacteria have a long history of safe use and most strains are considered commensal microorganisms with no pathogenic potential.

Screening of intestinal microflora for effective probiotic bacteria.

Increasing consumer awareness of health-promoting intestinal bacteria has fueled the addition of viable probiotic bacteria as functional ingredients in certain foods. However, to effectively market the enhanced attributes of these foods, the added probiotic bacteria need to have scientific credibility. The scientific rationale for using many of the strains of probiotic bacteria currently on the market is weak. Furthering the current understanding of what features a bacterium needs to have for effective probiotic functionality will enable the selection of strains with a more credible scientific rationale. To screen for effective strains, one must understand the microbial diversity in the intestines of healthy individuals. The advent of molecular tools has greatly enhanced our ability to accomplish this. These tools comprise genetic fingerprinting, specific probes, molecular speciation, and techniques for the in situ analysis of specific microbial groups in the intestine. This review will detail these scientific approaches and how their impact will improve criteria for selection of probiotic bacteria.

Effect of milk supplementation and culture composition on acidification, textural properties and microbiological stability of fermented milks containing probiotic bacteria

In the present work, the combined effect of milk supplementation and culture composition on acidification, textural properties, and microbiological stability of fermented milks containing probiotic bacteria, was studied. Three powders (whey, casein hydrolysate, and milk proteins) were tested as supplementation. Two strains of probiotic bacteria, Lactobacillus acidophilus (LA5) and Lactobacillus rhamnosus (LC35), were used in pure culture, and in mixed culture with Streptococcus thermophilus (ST7). Acidifying activity was enhanced with mixed cultures, compared to pure cultures resulting in a shorter time to reach pH 4.5. Acidifying activity was greatly improved with casein hydrolysate, with a reduction of the fermentation time by about 55% by comparison with the other supplementations. The stability of probiotic bacteria was weakly affected by milk supplementation and culture composition. However, pure cultures were more stable than mixed cultures. The texture of the fermented products was not dependent on culture composition, but strongly dependent on milk supplementation. Sweet whey supplementation gave products with lower firmness and viscoelasticity than products supplemented with casein hydrolysate or milk proteins (decrease by 70%). It was observed that all products containing probiotic counts over 2.2×107 CFU mL−1 are suitable for the development of a lactic beverage containing probiotics.

Acute oral toxicity and bacterial translocation studies on potentially probiotic strains of lactic acid bacteria

Three potentially probiotic lactic acid bacteria (LAB) strains, Lactobacillus rhamnosus HN001 (DR20 TM), Lb. acidophilus HN017 and Bifidobacterium lactis HN019 (DR10 ™), have recently been identified and characterized. The present study was designed to evaluate the acute oral toxicity of these strains to mice, and also to investigate bacterial translocation and gut mucosal pathology in BALB/c mice fed HN019, HN001 or HN017 for 8 consecutive days at a high dose of 10 11cfu/mouse/day. Results showed that these probiotic strains had no adverse effect on general health status, feed intake, body weight gain and intestinal mucosal morphology (villus height, crypt depth, epithelial cell height and mucosal thickness). No viable bacteria were recovered from blood and tissue samples (mesenteric lymph nodes, liver and spleen) of mice, and no treatment-associated illness or death was observed. According to these results, the oral LD 50 of HN019, HN001 and HN017 is more than 50 g/kg/day for mice, and their acceptable daily intake (ADI) value is 35 g dry bacteria per day for a 70-kg person. This suggests that the probiotic strains HN019, HN001 and HN017 are non-pathogenic and likely to be safe for human consumption.

A Probiotic Strain of L. Acidophilus Reduces DMH-Induced Large Intestinal Tumors in Male Sprague-Dawley Rats

Probiotic bacteria strains were examined for their influence on 1,2-dimethylhydrazine (DMH)-induced intestinal tumors in 100 male Sprague-Dawley rats. Lactobacillus acidophilus (Delvo Pro LA-1), Lactobacillus rhamnosus (GG), Bifidobacterium animalis (CSCC1941), and Streptococcus thermophilus (DD145) strains were examined for their influence when added as freeze-dried bacteria to an experimental diet based on a high-fat semipurified (AIN-93) rodent diet. Four bacterial treatments were compared: L. acidophilus, L. acidophilus + B. animalis, L. rhamnosus, and S. thermophilus, the bacteria being added daily at 1% freeze-dried weight (10 10 colony-forming units/g) to the diet. Trends were ob-served in the incidence of rats with large intestinal tumors for three treatments: 25% lower than control for L. acidophilus, 20% lower for L. acidophilus + B. animalis and L. rhamnosus treatments, and 10% lower for S. thermophilus. Large intestinal tumor burden was significantly lower for treated rats with L. acidophilus than for the control group (10 and 3 tumors/treatment group, respectively, p = 0.05). Large intestinal tumor mass index was also lower for the L. acidophilus treatment than for control (1.70 and 0.10, respectively, p = 0.05). Other treatments showed no statistically significant change from control for these indexes of tumorigenesis. For rats fed L. acidophilus, no adenocarcinomas were present in the colons. Pulsed-field gel electro-phoresis of bacterial chromosomal DNA fragments was used to differentiate introduced (exogenous) bacterial strains from indigenous bacteria of the same genera present in the feces. Survival during gut passage and displacement of indigenous lactobacilli occurred with introduced L. acidophilus and L. rhamnosus GG during the probiotic treatment period. However, introduced strains of B. animalis and S. thermophilus were not able to be isolated from feces. It is concluded that this strain of L. acidophilus supplied as freeze-dried bacteria in the diet was protective, as seen by a small but significant inhibition of tumors within the rat colon.

Antiproliferative effects of homogenates derived from five strains of candidate probiotic bacteria.

Unheated and heat-treated homogenates were separately prepared from candidate probiotic bacteria, including Lactobacillus rhamnosus GG, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Streptococcus thermophilus. We compared the phytohemagglutinin-induced proliferation of mononuclear cells in the presence of homogenates and in the presence of a control containing no homogenate by assessing thymidine incorporation in cell cultures. All homogenates suppressed proliferation, whether the enzymatic activity was inactivated or not inactivated by heating. When the proliferation assays were repeated with cytoplasmic and cell wall extracts derived from the homogenate of L. rhamnosus GG, the cytoplasmic extract but not the cell wall extract was suppressive. These findings indicate that candidate probiotic bacteria possess a heat-stable antiproliferative component(s). These bacteria may be used to generate microbiologically nonviable yet immunologically active probiotic food products that are easier to store and have a longer shelf life.

Aflatoxin B1 Binding Abilities of Probiotic Bacteria

The detoxification ability and toxin binding properties (ability and strength) of aflatoxin B1 by six strains of probiotic bacteria were studied. The detoxification ability of the organisms ranged between 20-50%. About 60-80% of the bound aflatoxin was removed when washed with water, and only 10-40% of the toxin was strongly bound to the bacterial cells. Among the organisms studied, Bifidobacterium infantis 1912 demonstrated a significantly higher aflatoxin binding ability than the other strains, while Bifidobacterium pseudolongum 20099 showed the least aflatoxin binding ability of about 10% of the added 50 ng of aflatoxin B1. Bifidobacterium bifidum 1 showed the least aflatoxin B1 binding strength during the 180 min treatment.

Lactic acid bacteria with health claims—interactions and interference with gastrointestinal flora

Lactic acid bacteria in foods have a long history of safe use. Members of the genera Lactococcus and Lactobacillus have a ‘generally-recognised-as-safe’ status, whilst members of the genera Streptococcus and Enterococcus and some other genera of lactic acid bacteria contain opportunistic pathogens. New species and more specific strains of probiotic bacteria are constantly being identified. Prior to incorporating new strains into products their efficacy should be carefully assessed and a case-by-case evaluation of whether they share the safety status of traditional food-grade organisms should be made. Genetically modified organisms are by definition always novel. Any safety assessment is based on the decision of the novel status, including phenotypic and genotypic characterisation. Additionally, for genetically modified organisms and their products, information is required in the following categories: effects of the genetic modification on the properties of the host organism, genetic stability of the genetically modified organism, specificity of expression of novel genetic material, transfer of genetic material from genetically modified organisms, and the ability of genetically modified microorganisms to colonise and to survive in the human gut.

Demonstration of safety of probiotics — a review

Probiotics are commonly defined as viable microorganisms (bacteria or yeasts) that exhibit a beneficial effect on the health of the host when they are ingested. They are used in foods, especially in fermented dairy products, but also in pharmaceutical preparations. The development of new probiotic strains aims at more active beneficial organisms. In the case of novel microorganisms and modified organisms the question of their safety and the risk to benefit ratio have to be assessed. Lactic acid bacteria (LAB) in foods have a long history of safe use. Members of the genera Lactococcus and Lactobacillus are most commonly given generally-recognised-as-safe (GRAS) status whilst members of the genera Streptococcus and Enterococcus and some other genera of LAB contain some opportunistic pathogens. Lactic acid bacteria are intrinsically resistant to many antibiotics. In many cases resistances are not, however, transmissible, and the species are also sensitive to many clinically used antibiotics even in the case of a lactic acid bacteria- associated opportunistic infection. Therefore no particular safety concern is associated with intrinsic type of resistance. Plasmid-associated antibiotic resistance, which occasionally occurs, is another matter because of the possibility of the resistance spreading to other, more harmful species and genera. The transmissible enterococcal resistance against glycopeptide antibiotics (vancomycin and teicoplanin) is particularly noteworthy, as vancomycin is one of the last effective antibiotics left in the treatment of certain multidrug-resistant pathogens. New species and more specific strains of probiotic bacteria are constantly identified. Prior to incorporating new strains into products their efficacy should be carefully assessed, and a case by case evaluation as to whether they share the safety status of traditional food-grade organisms should be made. The current documentation of adverse effects in the literature is reviewed. Future recommendations for the safety of already existing and new probiotics will be given.