Comprehensive approaches for assessing the safety of probiotic bacteria

The potential of probiotics in the amelioration of hyperuricemia

Hyperuricemia is a common disease caused by metabolic disorders or the excessive intake of high-purine foods. Persistent hyperuricemia in extreme cases induces gout, and asymptomatic hyperuricemia is probably linked to other metabolic diseases, such as hypertension. The typical damage caused by asymptomatic hyperuricemia includes inflammation, oxidative stress and gut dysbiosis. Probiotics have broad potential applications as food additives, not as drug therapies, in the amelioration of hyperuricemia. In this review, we describe novel methods for potential hyperuricemia amelioration with probiotics. The pathways through which probiotics may ameliorate hyperuricemia are discussed, including the decrease in uric acid production through purine assimilation and XOD (xanthine oxidase) inhibition as well as enhanced excretion of uric acid production by promoting ABCG2 (ATP binding cassette subfamily G member 2) activity, respectively. Three possible probiotic-related therapeutic pathways for alleviating the syndrome of hyperuricemia are also summarized. The first mechanism is to alleviate the oxidation and inflammation induced by hyperuricemia through the inhibition of NLRP3 inflammasome, the second is to restore damaged intestinal epithelium barriers and prevent gut microbiota dysbiosis, and the third is to enhance the innate immune system by increasing the secretion of immunoglobulin A (sIgA) to resist the stimulus by hyperuricemia. We propose that future research should focus on superior strain resource isolation and insight into the cause-effect mechanisms of probiotics for hyperuricemia amelioration. The safety and effects of the application of probiotics in clinical use also need verification.

Evaluation of inhibitory and probiotic properties of lactic acid bacteria isolated from vaginal microflora

Lactic acid bacteria (LABs) are known to secrete species-specific secondary metabolites that could be utilized as novel therapeutics against multi-drug resistant pathogens. This study aimed to investigate the antagonistic and probiotic properties of LABs isolated from the vaginal ecosystem of healthy women and to assess the stability of their antagonistic metabolites. Among 43 strains isolated from healthy women, eight LAB strains exhibited detectable BLISs (bacteriocin-like substances) producing ability against E. faecalis (JH-86), S. aureus (JH-68), Streptococcus sp. (JH-80), and E. coli (JH-101), with zone of inhibition (ZI) ranging from 9.00 to 20.33 mm and minimum inhibitory concentrations (MICs) from 62.5 to 500 μL/mL, respectively. The partially purified compounds extracted from cell free supernatant (CFS) displayed an increase in antagonistic activity based on ZI, 9.67-30.17 mm and MICs, 3.91-15.63 mg/mL, respectively. In a time-kill study, both crude and partially purified compounds of Limosilactobacillus reuteri (MT180537), Pediococcus pentosaceus (MT176555), Limosilactobacillus pontis (MW362838), and Levilactobacillus brevis (MW362790) exhibited significant bactericidal action against E. faecalis (MW051601), the most frequent etiological agent of aerobic vaginitis (AV). The active secondary metabolites from L. reuteri (MT180537), P. pentosaceus (MT176555), and L. pontis (MW362838) were protein in nature and remained stable under different physicochemical conditions. Regarding probiotic properties, the strains presented probiotic characteristics, i.e., good acid, bile salt tolerance, aggregation properties, and biofilm formation. The strains were susceptible to most of the commonly used antibiotics and had no hemolytic activity. In conclusion, antagonistic compounds or BLIS produced by L. reuteri (MT180537) could be investigated further for preparation of ointments to treat AV.

In silico, in vitro and in vivo safety evaluation of Limosilactobacillus reuteri strains ATCC PTA-126787 & ATCC PTA-126788 for potential probiotic applications

The last two decades have witnessed a tremendous growth in probiotics and in the numbers of publications on their potential health benefits. Owing to their distinguishing beneficial effects and long history of safe use, species belonging to the Lactobacillus genus are among the most widely used probiotic species in human food and dietary supplements and are finding increased use in animal feed. Here, we isolated, identified, and evaluated the safety of two novel Limosilactobacillus reuteri (L. reuteri) isolates, ATCC PTA-126787 & ATCC PTA-126788. More specifically, we sequenced the genomes of these two L. reuteri strains using the PacBio sequencing platform. Using a combination of biochemical and genetic methods, we identified the two strains as belonging to L. reuteri species. Detailed in silico analyses showed that the two strains do not encode for any known genetic sequences of concern for human or animal health. In vitro assays confirmed that the strains are susceptible to clinically relevant antibiotics and do not produce potentially harmful by-products such as biogenic amines. In vitro bile and acid tolerance studies demonstrated that the two strains have similar survival profiles as the commercial L. reuteri probiotic strain DSM 17938. Most importantly, daily administration of the two probiotic strains to broiler chickens in drinking water for 26 days did not induce any adverse effect, clinical disease, or histopathological lesions, supporting the safety of the strains in an in vivo avian model. All together, these data provide in silico, in vitro and in vivo evidence of the safety of the two novel candidates for potential probiotic applications in humans as well as animals.

Consumer's acceptability and health consciousness of probiotic and prebiotic of non-dairy products

Human gut microbiota is a protective agent of intestinal and systemic health, and its modulation is of great interest for human wellbeing. In the world of biotics, besides probiotics, prebiotics, and synbiotics, also appears the denomination of "postbiotics" and "psychobiotics". Fermented dairy products are, traditionally, the major source of probiotics. Nevertheless, due to the increasing number of lactose-intolerant individuals and strict vegetarians, there is a need for innovative non-dairy products. Non-dairy biotics are being included in the normal diet and due to technological advances, many products are created using non-conventional food matrices like kombucha tea, herbal tea, baking mix, and cereal-based products. The microorganisms most used as probiotics in many of the non-dairy products are strains belonging to the genera Bifidobacterium, Enterococcus, Lactobacillus, Lactococcus, Streptococcus, and Bacillus, and some yeast strains namely Saccharomyces cerevisiae var. boulardii. Recently, several other yeasts have been described as having probiotic properties. This review describes gut-derived effects in humans of possible microorganisms, such as yeasts, and bacteria, isolated from non-dairy fermented and non-fermented foods and beverages. The microorganisms responsible for the processing of these non-dairy fermented products, together with the prebiotics, form a class of nutrients that have been proven to be beneficial for our gut health.

Analysis of the probiotic activity of Bacillus velezensis RT-26 strain isolated from reindeer rumen by whole-genome sequencing

The paper analyses the properties of Bacillus velezensis RT-26, a probiotic strain isolated from reindeer rumen, which has high activity towards fiber degradation, against bacterial and fungal pathogens. The analysis was performed using whole-genome sequencing of the strain using the Illumina platform. The study revealed that strain RT-26 possessed a complete set of metabolic pathways, including glycolysis, the tricarboxylic acid cycle, and the pentose phosphate pathway. 411 genes were involved in carbohydrate metabolism in the strain genome, 229 genes were related to vitamin and coenzyme metabolism, 149 genes were involved in fatty acid metabolism. The synthesis pathways of various amino acids, most B vitamins (thiamine, riboflavin, nicotiamide, vitamin B5) were identified in the genome. A complete pathway for synthesis of the dipeptide antibiotic bacilisin was detected in the strain. In addition, the strain is capable of synthesizing class A beta-lactamase. No genes responsible for the degradation of mycotoxins and xenobiotics were detected in the genome of the strain studied. A number of glycosyl hydrolase families were detected in the strain genome: GH 1, 3, 4, 5, 6, 11, 13, 16, 18, 20, 23, 26, 28, 30, 32, 43, 46, 51, 53, 68, 68, 73, 101, 109, 126. Carbohydrate-binding proteins were of the SVM 50 family. Glycosyltransferases were of GT 1, 2, 4, 8, 26, 28, 30, 51, 83 families. In the genome of Bacillus velezensis strain RT-26, cellulases related to families GH 5, 6, 26, 51, chitinases related to families GH 18 and 23, and xylanases related to families GH 1, 3, 4, 16, 30, 43 were found. Thus, strain B. velezensis RT-26 has several phenotypically and genotypically proven properties that can characterize it as a good probiotic microorganism.

Assessment of the Safety of Lactobacillus casei IMV B-7280 Probiotic Strain on a Mouse Model

Probiotics, in particular Lactobacillus (lactic acid bacteria, LAB) strains, are widely used in clinical practice. Despite that these probiotics have GRAS (generally regarded as safe) and qualified presumption of safety (QPS) statuses, the safety of particular strains still needs to be thoroughly studied. The aim of the study was to evaluate the safety of Lact. casei IMV B-7280 strain by investigating toxicity and the effects on gut microbiota in experimental animal model. Male BALB/c mice (7-8 weeks, weight 20-24 g) were treated with amounts of Lact. casei IMV B-7280 strain: 5 × 106, 5 × 108, or 5 × 109 CFU/animal once per day during 7 days, or in the amount of 1 × 1010 CFU/animal once per day during 3 days (most of the proposed probiotic doses for humans-from 108 to 109 CFU) and monitored during 14 days. Blood tests and serum biochemistry were conducted; the cecal content from mice of the experimental and control groups were freshly collected and analyzed. At the end of the experiments (15th day), the presence of LAB in the heart, liver, kidney, and mesenteric lymph nodes and peripheral blood was determined; histology of the brain, liver, heart, fragments of the small and large intestine, and mesenteric lymph nodes was conducted. Survival rate of BALB/c mice treated with Lact. casei IMV B-7280 strain in different concentrations in toxicity experiments during 14 days was 100%. We observed no signs of toxicity as changes in gait, lethargy, sleep, somatomotor activity as well as changes in fur, eyes, skin and mucous membranes, tremors, behavior pattern, convulsions, salivation, diarrhea, and local injuries in mice from all experimental groups. After administration of probiotic strain, the number of opportunistic bacteria in cecal contents, such as Staphylococcus spp., Candida spp., Pseudomonas spp., and total aerobic and optionally anaerobic bacteria decreased compared to controls; the population of beneficial bacteria such as lactobacilli increased in cecal contents of these mice. LAB were not detected in the peripheral blood, heart, liver, kidneys, and mesenteric lymph nodes after administration of this strain to intact mice. Lact. casei IMV B-7280 strain is safe at dose up to 1010 CFU/animal during 3- and 7-day oral administration to mice and has a positive effect on the gut microbiota composition; it could be potentially considered as safe probiotic for humans.

Ameliorative Effect of Surface Proteins of Probiotic Lactobacilli in Colitis Mouse Models

The increase in concern from viable cells of probiotics specifically in acute inflammatory conditions has led to the emergence of the concept of postbiotics as a safer alternative therapy in the field of health and wellness. The aim of the present study was to evaluate the efficacy of surface proteins from three probiotic strains in dextran sodium sulfate and trinitrobenzenesulphonic acid = induced colitis mouse models. The molecular weight of total surface proteins extracted from the three probiotic strains ranged from ∼25 to ∼250 kDa with the presence of negligible levels of endotoxins. Surface layer proteins (SLPs) (∼45 kDa) were found to be present only in the Lactobacillus acidophilus NCFM strain. In the in vivo study, significant differences were not observed in the weight loss and general appetite, however, the decrease in colon length was apparent in TNBS colitis control mice. Further, the administration of these surface proteins significantly reversed the histopathological damages induced by the colitogens and improved the overall histological score. The oral ingestion of these surface proteins also led to a decrease in myeloperoxidase activity and TNF-α expression while the IL-10 levels significantly increased for the strain NCFM followed by MTCC 5690 and MTCC 5689. Overall, the present study signifies the ameliorative role of probiotic surface proteins in colitis mice, thereby, offering a potential and safer alternative for the management of inflammatory bowel disorders.

In vitro gastrointestinal resistance of Lactobacillus acidophilus in some dairy products

In this study, different dairy products such as ice cream, yoghurt, white pickled cheese, and fermented acidophilus milk were manufactured by using either Lactobacillus acidophilus DSM 20,079 or Lactobacillus acidophilus NCFM. The counts of L. acidophilus in the samples on days 1, 15, and 30 of the storage were determined. Additionally, the samples contained L. acidophilus were passed through a dynamic gastrointestinal model designed in laboratory conditions to compare the protective effect of different dairy products on viability of L. acidophilus against stress factors of the gastrointestinal model. The counts of L. acidophilus NCFM and L. acidophilus DSM 20,079 in the samples decreased by between 0.04 and 0.37 log units and by between 0.11 and 0.27 log units, respectively, within 30 days of storage. During the passage through the gastrointestinal model, the highest percentage reduction in the counts of L. acidophilus was determined in yoghurt followed by fermented acidophilus milk, white pickled cheese, and ice cream, respectively. The reduction in the counts of L. acidophilus in the samples during the passage through the model increased with extension of storage time. The results of this study showed that the reduction in the counts L. acidophilus in the samples during the passage through the model was influenced significantly by the matrix of the dairy product and storage period.

Safety Evaluation of Lactobacillus delbrueckii subsp. lactis CIDCA 133: a Health-Promoting Bacteria

Lactobacillus delbrueckii subsp. lactis CIDCA is a new potential probiotic strain whose molecular basis attributed to the host's benefit has been reported. This study investigated the safety aspects of Lactobacillus delbrueckii subsp. lactis CIDCA 133 based on whole-genome sequence and phenotypic analysis to avoid future questions about the harmful effects of this strain consumption. Genomic analysis showed that L. delbrueckii subsp. lactis CIDCA 133 harbors virulence, harmful metabolites, and antimicrobial resistance-associated genes. However, none of these genetic elements is flanked or located within prophage regions and plasmid sequence. At a phenotypic level, it was observed L. delbrueckii subsp. lactis CIDCA 133 antimicrobial resistance to aminoglycosides streptomycin and gentamicin antibiotics, but no hemolytic and mucin degradation activity was exhibited by strain. Furthermore, no adverse effects were observed regarding mice clinical and histopathological analysis after the strain consumption (5 × 10⁷ CFU/mL). Overall, these findings reveal the safety of Lactobacillus delbrueckii subsp. lactis CIDCA 133 for consumption and future probiotic applications.

Safety Evaluation of Bifidobacterium lactis BL-99 and Lacticaseibacillus paracasei K56 and ET-22 in vitro and in vivo

Probiotics have been reported to play a major role in maintaining the balance of microbiota in host. Consumption of food with probiotics has increased with consumer concerns regarding healthy diets and wellness. Correspondingly, safety evaluation of probiotics for human consumption has become increasingly important in food industry. Herein, we aimed to test the safety of Bifidobacterium lactis BL-99 and Lacticaseibacillus paracasei K56 and ET-22 strains in vitro and in vivo. In results, these strains were found to be negative for mucin degradation and platelet aggregation test. Additionally, the three strains were susceptible to eight antibiotics. In accordance with bacterial reversion mutation (Ames) assay, the tested strains had no genetic mutagenicity. Finally, it was confirmed that there were no dose-dependent mortality and toxicity throughout multidose oral toxicity tests in rats. Our findings demonstrated that B. lactis BL-99 and L. paracasei K56 and ET-22 can achieve the generally recognized as safe (GRAS) status as probiotics in the future.

The Administration of Probiotics against Hypercholesterolemia: A Systematic Review

Hypercholesterolemia is a key factor in the progression of atherosclerosis and cardiovascular disease (CVD). CVD is a significant public health concern with a high death rate. Some of the main factors linked to CVD include genetics and lifestyle. Dyslipidemia has been one of the factors related to the onset of several CVD-related diseases. Several clinicopathological studies have shown a correlation between high cholesterol levels, particularly low-density lipoprotein cholesterol (LDL-c), and CVD development. Probiotics have received a lot of attention for various beneficial effects, especially their ability to reduce blood cholesterol in humans. Probiotics were shown in several investigations to affect hypercholesterolemia by influencing cholesterol biosynthesis. The current review focuses on the human dietary interventions with probiotics and their effects on CVD risk factors and hypercholesterolemia. The outcomes are debatable and consider various parameters such as probiotic strain, dosing frequency, therapeutic response, dietary changes, and so forth. As a result, probiotics have the propensity to become dietary supplements in moderate/severe hypercholesterolemic patients, which significantly reduces the CVD risk.

Marination liquids enriched with probiotics and their inactivation effects against food-borne pathogens inoculated on meat

The aim of the study was to develop marination liquids (MLs) enriched with probiotics (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus or their combination) to improve the safety and sensory quality of meat during marination. The total acidity, total phenolic content, antioxidant and antimicrobial activities of MLs were in the range of 0.70-0.92 g tartaric acid/100 mL, 331.00-513.80 mg GAE/L, 71.10%-93.37% and 6.50-10.00 mm, respectively. At the end of the marination, the numbers of Escherichia coli O157: H7, Listeria monocytogenes and Salmonella Typhimurium on meat samples (≅6 log CFU/g) were decreased in the range of 0.7-2.7, 2.1-3.3 and 0.8-2.0 log CFU/g, respectively, depending on the type of ML and the treatment time used. Additionally, meat sample marinated with MLs containing L. casei was the most preferred sample in terms of appearance, color, flavor and general acceptability. These results showed that the existing effects of koruk juice were increased by probiotics.

Functional group characterization of lactic bacterial biosurfactants and evaluation of antagonistic actions against clinical isolates of methicillin-resistant Staphylococcus aureus

The present study investigated the antimicrobial and antibiofilm potential of biosurfactants derived from Lactobacillus fermentum Lf1, L. fermentum LbS4 and Lactobacillus plantarum A5 against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). The cell wall-bound and intracellular biosurfactants were extracted by solvent extraction method. Fourier-transform infrared spectroscopy-based characterization of biosurfactants revealed the heterogeneous chemical composition involving proteins, fatty acids and carbohydrate moieties in LbS4 and A5, while only the sugar and lipid fractions in Lf1. Fatty acid profiling using Gas chromatography-mass spectrometry indicated hexadecanoic acid and stearic acid as the predominant fatty acids in the biosurfactants of all these strains. Biosurfactants demonstrated dose-dependent antibacterial action against MRSA isolates with the highest inhibition zone diameter (30·0 ± 0·0 to 35·0 ± 0·0 mm) recorded at 400 mg ml^-1 . Biosurfactants showed an excellent staphylococcal antibiofilm activity by preventing the biofilm formation and disrupting the preformed biofilms. Visual inspection through scanning electron microscopy witnessed the biosurfactants-induced alteration in the cell membrane integrity and subsequent membrane pore formation on staphylococcal cells. Taken together, our findings emphasize the prospects of biomedical applications of biosurfactants as bactericidal and biofilm controlling agents to confront staphylococcal nosocomial infections.

Protective and ameliorating effects of probiotics against diet-induced obesity: A review

Diet-induced obesity is one of the major public health concerns all over the world, and obesity also contributes to the development of other chronic diseases such as non-alcoholic fatty acid liver disease, type 2 diabetes mellitus and cardiovascular diseases. Evidence shows that the pathogenesis of obesity and obesity-associated chronic diseases are closely related to dysregulation of lipid metabolism, glucose metabolism and cholesterol metabolism, and oxidative stress, endoplasmic reticulum stress, abnormal gut microbiome and chronic low-grade inflammation. Recently, in view of potential effects on lipid metabolism, glucose metabolism, cholesterol metabolism and intestinal microbiome, as well as anti-oxidative and anti-inflammatory activities, natural probiotics, including live and dead probiotics, and probiotic components and metabolites, have attracted increasing attention and are considered as novel strategies for preventing and ameliorating obesity and obesity-related chronic diseases. Specifically, this review is presented on the anti-obesity effects of probiotics and underlying molecular mechanisms, which will provide a theoretical basis of anti-obesity probiotics for the development of functional foods.

Lacticaseibacillus rhamnosus Reduces the Pathogenicity of Escherichia coli in Chickens

Lacticaseibacillus rhamnosus is a recognized probiotic that is widely used in scientific research and clinical applications. This study found that the Lacticaseibacillus rhamnosus GG (LGG) strain can reduce the adhesion of Escherichia coli (E. coli) to primary chicken intestinal epithelial cells by 75.7% and inhibit 41.7% of the E. coli that adhere to intestinal epithelial cells. Additionally, LGG showed strong inhibitory ability on the growth of E. coli, Staphylococcus aureus, Salmonella Paratyphi B, and Salmonella Enteritidis in vitro. Furthermore, the influence of LGG on the growth performance, intestinal flora, immunity, and disease resistance of chickens was explored. Chickens fed with LGG exhibited increased average daily weight gain and concentrations of sIgA, IgG, and IgM than did controls. After 21 days of feeding, a diet with LGG increased the diversity of intestinal microbiota and maintained intestinal health. Moreover, LGG promoted immunologic barriers by upregulating cytokines and chemokines via the Toll-like receptor. The major pro-inflammatory factors, including Myd88, NF-κB, Il6, and Il8, were upregulated compared to controls. After being challenged with E. coli, the survival rate of chickens fed with LGG was significantly higher than those in the control group, and decreased numbers of E. coli were detected in the heart and lungs of the LGG group. In summary, oral administration of LGG to chickens could improve growth performance, maintain intestinal homeostasis, and enhance innate immune response and disease resistance.

Safety assessment of Streptococcus salivarius DB-B5 as a probiotic candidate for oral health

Streptococcus salivarius DB-B5 was previously isolated from the supragingival plaque of a healthy female adult and selected for development as a probiotic candidate for oral health. Probiotics are an important emerging therapeutic method for preventing, treating, and maintaining oral health. Although S. salivarius is a predominant member of the commensal oral microbiota and generally regarded as a safe species, it is recognized that each strain needs to be comprehensively assessed for safety. This study describes the in silico, in vitro, and clinical testing that were conducted to evaluate the safety of S. salivarius DB-B5. Both 16S rRNA and multi-gene phylogenetic reconstruction was used to confirm the taxonomic identity of this strain. Bioinformatic analysis of the genome demonstrated the absence of transmissible antibiotic resistance genes or virulence factors. Phenotypic testing further showed S. salivarius DB-B5 to be susceptible to clinically relevant antibiotics. S. salivarius DB-B5 displayed weak alpha-hemolysis, and does not produce biogenic amines. In a randomized, double-blind, placebo-controlled clinical study, consumption of S. salivarius DB-B5 at 10 billion CFU/day for 4 weeks by healthy adults was safe and well-tolerated (ClinicalTrials.gov registry number NCT04492631). This work has indicated that S. salivarius DB-B5 is a safe probiotic candidate.

Invited review: Characterization of new probiotics from dairy and nondairy products-Insights into acid tolerance, bile metabolism and tolerance, and adhesion capability

The selection of potential probiotic strains that possess the physiological capacity of performing successfully in the gastrointestinal tract (GIT) is a critical challenge. Probiotic microorganisms must tolerate the deleterious effects of various stresses to survive passage and function in the human GIT. Adhesion to the intestinal mucosa is also an important aspect. Recently, numerous studies have been performed concerning the selection and evaluation of novel probiotic microorganisms, mainly probiotic bacteria isolated from dairy and nondairy products. Therefore, it would be crucial to critically review the assessment methods employed to select the potential probiotics. This article aims to review and discuss the recent approaches, methods used for the selection, and outcomes of the evaluation of novel probiotic strains with the main purpose of supporting future probiotic microbial assessment studies. The findings and approaches used for assessing acid tolerance, bile metabolism and tolerance, and adhesion capability are the focus of this review. In addition, probiotic bile deconjugation and bile salt hydrolysis are explored. The selection of a new probiotic strain has mainly been based on the in vitro tolerance of physiologically related stresses including low pH and bile, to ensure that the potential probiotic microorganism can survive the harsh conditions of the GIT. However, the varied experimental conditions used in these studies (different types of media, bile, pH, and incubation time) hamper the comparison of the results of these investigations. Therefore, standardization of experimental conditions for characterizing and selecting probiotics is warranted.

Gut Microbiota: Influence on Carcinogenesis and Modulation Strategies by Drug Delivery Systems to Improve Cancer Therapy

Gut microbiota have close interactions with the host. It can affect cancer progression and the outcomes of cancer therapy, including chemotherapy, immunotherapy, and radiotherapy. Therefore, approaches toward the modulation of gut microbiota will enhance cancer prevention and treatment. Modern drug delivery systems (DDS) are emerging as rational and promising tools for microbiota intervention. These delivery systems have compensated for the obstacles associated with traditional treatments. In this review, the essential roles of gut microbiota in carcinogenesis, cancer progression, and various cancer therapies are first introduced. Next, advances in DDS that are aimed at enhancing the efficacy of cancer therapy by modulating or engineering gut microbiota are highlighted. Finally, the challenges and opportunities associated with the application of DDS targeting gut microbiota for cancer prevention and treatment are briefly discussed.

A Comprehensive Assessment of the Safety of Blautia producta DSM 2950

In recent years, Blautia has attracted attention for its role in ameliorating host diseases. In particular, Blautia producta DSM 2950 has been considered a potential probiotic due to its ability to mitigate inflammation in poly(I:C) induced HT-29 cells. Thus, to promote the development of indigenous intestinal microorganisms with potential probiotic function, we conducted a comprehensive experimental analysis of DSM 2950 to determine its safety. This comprised a study of its potential virulence genes, antibiotic resistance genes, genomic islands, antibiotic resistance, and hemolytic activity and a 14-day test of its acute oral toxicity in mice. The results indicated no toxin-related virulence genes in the DSM 2950 genome. Most of the genomic islands in DSM 2950 were related to metabolism, rather than virulence expression. DSM 2950 was sensitive to most of the tested antibiotics but was tolerant of treatment with kanamycin, neomycin, clindamycin, or ciprofloxacin, probably because it possessed the corresponding antibiotic resistance genes. Oral acute toxicity tests indicated that the consumption of DSM 2950 does not cause toxic side effects in mice. Overall, the safety profile of DSM 2950 confirmed that it could be a candidate probiotic for use in food and pharmaceutical preparations.

Evolutionary concepts in the functional biotics arena: a mini-review

Over the years, the attempts to elucidate the role of beneficial microorganisms in shaping human health are becoming fairly apparent. The functional impact conferred by such microbes is not only transmitted by viable cells or their metabolites but also through non-viable cells. Extensive research to unveil the protective action of such wonder bugs has resulted in categorizing the beneficial microflora and their bioactive metabolites into a variety of functional biotic concepts based on their intended applications in various forms. In the modern era, these are often termed as probiotics, prebiotics, synbiotics, postbiotics, next-generation probiotics, psychobiotics, oncobiotics, pharmabiotics, and metabiotics. Currently, the concept of traditional probiotics is being widened to include microbes beyond lactic acid bacteria. Indeed, this diversification has broadened the functional food portfolio from food to pharmaceuticals. In this context, the present review aims to summarize the existing biotic concepts and their differences thereof.

Whole-genome analysis of probiotic product isolates reveals the presence of genes related to antimicrobial resistance, virulence factors, and toxic metabolites, posing potential health risks

Background

Safety issues of probiotic products have been reported frequently in recent years. Ten bacterial strains isolated from seven commercial probiotic products on market were evaluated for their safety, by whole-genome analysis.

Results

We found that the bacterial species of three probiotic products were incorrectly labeled. Furthermore, six probiotic product isolates (PPS) contained genes for the production of toxic metabolites, while another three strains contained virulence genes, which might pose a potential health risk. In addition, three of them have drug-resistance genes, among which two strains potentially displayed multidrug resistance. One isolate has in silico predicted transferable genes responsible for toxic metabolite production, and they could potentially transfer to human gut microflora or environmental bacteria. Isolates of Lactobacillus rhamnosus and Bifidobacterium animalis subsp. lactis are associated with low risk for human consumption. Based on a comparative genome analysis, we found that the isolated Enterococcus faecium TK-P5D clustered with a well-defined probiotic strain, while E. faecalis TK-P4B clustered with a pathogenic strain.

Conclusions

Our work clearly illustrates that whole-genome analysis is a useful method to evaluate the quality and safety of probiotic products. Regulatory quality control and stringent regulations on probiotic products are needed to ensure safe consumption and protect human health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07539-9.

Metataxonomic analysis of microbiota from Pakistani dromedary camelids milk and characterization of a newly isolated Lactobacillus fermentum strain with probiotic and bio-yogurt starter traits

This study was undertaken to investigate the starter and probiotic potential of lactic acid bacteria isolated from dromedarian camel's milk using both culture-dependent and -independent approaches and metataxonomic analysis. Strains of lactic acid bacteria recovered were examined in vitro for tolerance to gastric acidity, bile, and lysozyme. Bile salt hydrolysis, serum cholesterol-lowering, oxalate degradation, proteolytic activity, exopolysaccharide production, and cell surface characteristics necessary for colonizing intestinal mucosa were also evaluated. A single strain of the species, Lactobacillus fermentum named NPL280, was selected through multivariate analysis as it harbored potential probiotic advantages and fulfilled safety criteria. The strain assimilated cholesterol, degraded oxalate, produced exopolysaccharides, and proved to be a proficient alternate yogurt starter with good viability in stored bio-yogurt. A sensorial analysis of the prepared bio-yogurt was also found to be exemplary. We conclude that the indigenous L. fermentum strain NPL280 has the desired traits of a starter and adjunct probiotic culture for dairy products.

Safety of Probiotics: Functional Fruit Beverages and Nutraceuticals

Over the last decade, fruit juice consumption has increased. Their rise in popularity can be attributed to the belief that they are a quick way to consuming a dietary portion of fruit. Probiotics added to fruit juices produce various bioactive compounds, thus probiotic fruit juices can be considered as a new type of functional foods. Such combinations could improve nutritional properties and provide health benefits of fruit juices, due to delivering positive health attributes from both sources (fruit juices and probiotics). However, this review discusses the other side of the same coin, i.e., the one that challenges general beliefs that probiotics are undoubtedly safe. This topic deserves more acknowledgments from the medical and nutritional literature, as it is highly important for health care professionals and nutritionists who must be aware of potential probiotic issues. Still, clinical trials have not adequately questioned the safety of probiotics, as they are generally considered safe. Therefore, this reviews aims to give an evidence-based perspective of probiotic safety, focusing on probiotic fruit beverages and nutraceuticals, by providing documented clinical case reports and studies. Finally, the paper deals with some additional insights from the pharmacological and toxicological point of views, such as pharmacological repercussions of probiotics on health.

Brazilian artisanal cheeses are rich and diverse sources of nonstarter lactic acid bacteria regarding technological, biopreservative, and safety properties-Insights through multivariate analysis

In this study a total of 220 isolates of lactic acid bacteria (LAB) recovered from 10 types of Brazilian artisanal cheeses marketed in 4 main regions of Brazil were evaluated regarding their safety and ability to produce diacetyl (a precursor of aromatic compounds), exopolysaccharides (EPS; from different sugar sources), and antagonistic activity against Listeria monocytogenes and Staphylococcus aureus. The results indicated that 131 isolates (59.6%) were classified as strong (40.5%) and moderate (19.1%) diacetyl producers; 28 isolates (12.7%) stood out due to their remarkable production of EPS from different sugars, including sucrose (3.2%), fructose (2.3%), lactose (2.3%), and glucose (6%). Furthermore, 94.1% and 95.9% of isolates presented antagonistic activity against S. aureus and L. monocytogenes, respectively, even though only 27 isolates (12.3%) exhibited positive results in the bacteriocin production test. None of the isolates tested presented hemolytic activity, and 117 were classified as safe, due to their intrinsic resistance to a maximum of 4 different antibiotics. The data obtained for assessment of antibiogram profile and technological potential (moderate and high production of diacetyl, EPS, and bacteriocins) were submitted to a multiple correspondence analysis to correlate them with the cheese of isolation. Regarding the antimicrobial profile of LAB strains, it was possible to verify an association between isolates from Minas artisanal cheeses from Araxá and resistance to tetracycline; Minas artisanal cheeses from Serro and resistance to erythromycin; Coalho and Minas artisanal cheese from Cerrado and resistance to penicillin; and isolates from Serrano and Colonial cheeses with clindamycin and ceftazidime resistance. Although the susceptibility of strains to these antibiotics was considered high (71.8-80.5%), these data may be related to the horizontal transfer of genes in the production chain of these cheeses. Results of multiple correspondence analysis also showed that isolates with antagonistic activity were mostly isolated from Manteiga, Colonial, and Coalho cheeses. The isolates with high or moderate EPS-producer ability from sucrose, glucose, and fructose were mainly associated with Minas artisanal cheeses from Cerrado. In contrast, isolates with high or moderate EPS-producer ability from lactose were isolated from Serrano, Minas artisanal cheeses from Canastra, and Campo das Vertentes microregions. Finally, isolates from Minas artisanal cheeses (from Araxá microregion), Coalho, and Caipira cheeses were associated with moderate/high diacetyl production. To the best of the authors' knowledge, this study provides, for the first time, data indicating that the dominant technological, biopreservative, and safety properties of LAB isolates can be correlated with the type of Brazilian artisanal cheeses, which denotes its singularity. This knowledge is of utmost relevance for the development of starter or adjunct cultures with tailored properties.

Microbial Etiology and Prevention of Dental Caries: Exploiting Natural Products to Inhibit Cariogenic Biofilms

Dental caries is one of the most common microbe-mediated oral diseases in human beings. At present, the accepted etiology of caries is based on a four-factor theory that includes oral microorganisms, oral environment, host, and time. Excessive exposure to dietary carbohydrates leads to the accumulation of acid-producing and acid-resistant microorganisms in the mouth. Dental caries is driven by dysbiosis of the dental biofilm adherent to the enamel surface. Effective preventive methods include inhibiting the cariogenic microorganisms, treatment with an anti-biofilm agent, and sugar intake control. The goal is to reduce the total amount of biofilm or the levels of specific pathogens. Natural products could be recommended for preventing dental caries, since they may possess fewer side effects in comparison with synthetic antimicrobials. Herein, the mechanisms of oral microbial community development and functional specialization are discussed. We highlight the application of widely explored natural products in the last five years for their ability to inhibit cariogenic microorganisms.

Characterization and ACE Inhibitory Activity of Fermented Milk with Probiotic Lactobacillus plantarum K25 as Analyzed by GC-MS-Based Metabolomics Approach

Addition of probiotics to yogurt with desired health benefits is gaining increasing attention. To further understand the effect of probiotic Lactobacillus plantarum on the quality and function of fermented milk, probiotic fermented milk (PFM) made with probiotic L. plantarum K25 and yogurt starter (L. delbrueckii ssp. bulgaricus and Streptococcus thermophilus) was compared with the control fermented milk (FM) made with only the yogurt starter. The probiotic strain was shown to survive well with a viable count of 7.1 ± 0.1 log CFU/g in the PFM sample after 21 days of storage at 4°C. The strain was shown to promote formation of volatiles such as acetoin and 2,3-butanediol with milk fragrance, and it did not cause post-acidification during refrigerated storage. Metabolomics analysis by GC-MS datasets coupled with multivariate statistical analysis showed that addition of L. plantarum K25 increased formation of over 20 metabolites detected in fermented milk, among which γ-aminobutyric acid was the most prominent. Together with several other metabolites with relatively high levels in fermented milk such as glyceric acid, malic acid, succinic acid, glycine, alanine, ribose, and 1,3-dihydroxyacetone, they might play important roles in the probiotic function of L. plantarum K25. Further assay of the bioactivity of the PFM sample showed significant (p < 0.05) increase of ACE inhibitory activity from 22.3% at day 1 to 49.3% at day 21 of the refrigerated storage. Therefore, probiotic L. plantarum K25 could be explored for potential application in functional dairy products.

Detection and isolation of the typical gut indigenous bacteria from ddY mice fed a casein-beef tallow-based or egg yolk-based diet

The effects of whole egg on the cecal microbiome of ddY mice has been reported. To investigate the existence of susceptible indigenous bacteria (SIB) to egg yolks (EY), mice were fed a diet containing either 20% (w/w) milk casein and 17% beef tallow (CT) or 12% milk casein and 27% EY for 14 days, and then, the cecal microbiome was analyzed by 16S rRNA (V4) amplicon sequencing. To isolate the typical species in each diet group, culture-dependent viable bacterial counts were determined on Blood Liver (BL) and Gifu Anaerobic Medium (GAM) agar plates. The amplicon sequencing analysis revealed typical CT-SIB, such as Lachnospiraceae-like bacteria, and EY-SIB, such as Allobaculum-, Lactobacillus murinus-, and Bacteroides vulgatus-like bacteria. Two of the detected SIB species, L. murinus- and B. vulgatus-like bacteria, were successfully isolated from the BL and GAM agar plates and defined using a 16S rDNA BLAST search. PRACTICAL APPLICATIONS: The SIB defined in the CT and EY groups might have some effects on the nutritional and functional chemical compounds in the milk casein, beef tallow, and/or EY. Analysis of its functional properties of the isolates might develop the new and unique probiotic strains.