Strain-level diversity of commercial probiotic isolates of Bacillus, Lactobacillus, and Saccharomyces species illustrated by molecular identification and phenotypic profiling

Effect of Bacillus subtilis and Bacillus coagulans spores on induced allergic contact dermatitis in dogs

BACKGROUND

Probiotic strains have the potential to modulate immune responses, reduce intestinal inflammation, normalize intestinal mucosal function and decrease allergic reactions.

OBJECTIVE

This study aimed to investigate the effect of oral probiotic supplements containing Bacillus subtilis and Bacillus coagulans spores on clinical symptoms, haematological factors and immune responses to allergic contact dermatitis in dogs induced by dinitrochlorobenzene (DNCB).

METHODS

DNCB was injected subcutaneously into the scapular region of 20 healthy adult dogs of both sexes, divided into four groups, to induce experimental allergic contact dermatitis. Dogs in Group 1 received food without probiotics or medication. Oral prednisolone was administered to Group 2 for 30 days at a dosage of 0.25 mg/kg every other day. The dogs in Group 3 were treated with a combination of oral prednisolone and probiotics. The dogs in Group 4 were fed daily with a mixture of 109 B. subtilis and B. coagulans bacteria for 30 days. The immune system responses and related gene expression were analysed in the treated animals.

RESULTS

The administration of probiotics for 30 days resulted in a reduction in clinical symptoms and duration of wound repair. The probiotics treatment also significantly increased the serum bactericidal effects against Staphylococcus aureus and Escherichia coli. It enhanced both the classic and alternative activity of the complement, as well as lysozyme activity. Additionally, the probiotics led to higher total immunoglobulin levels and significant reductions in anti-trypsin and C-reactive protein levels. Furthermore, the expression of IgE, induction of interferon-gamma and IL-4 genes were also reduced.

CONCLUSIONS

According to the results, B. subtilis and B. coagulans can be further investigated as a viable alternative to corticosteroids in treating allergic contact dermatitis in dogs.

Influence of connatural factors in shaping vaginal microflora and ensuring its health

Vaginal canal (VC) is exposed to the external environment affected by habitual factors like hygiene and sexual behaviour as well as physiological factors like puberty, menstrual cycle, pregnancy, child birth and menopause. Healthy VC harbours beneficial microflora supported by vaginal epithelium and cervical fluid. Connatural antimicrobial peptide (AMPs) of female reproductive tract (FRT) conjunctly with these beneficial microbes provide protection from a large number of infectious diseases. Such infections may either be caused by native microbes of the VC or transitory microbes like bacteria or virus which are not a part of VC microflora. This review highlight's the role of hormones, enzymes, innate immunological factors, epithelial cells and vaginal mucus that support beneficial microbes over infectious ones thus, helping to maintain homeostasis in VC and further protect the FRT. We also discuss the prospective use of vaginal probiotics and AMPs against pathogens which can serve as a potential cure for vaginal infections.

Recent and Advanced DNA-Based Technologies for the Authentication of Probiotic, Protected Designation of Origin (PDO) and Protected Geographical Indication (PGI) Fermented Foods and Beverages

The authenticity of probiotic products and fermented foods and beverages that have the status of protected designation of origin (PDO) or geographical indication (PGI) can be assessed via numerous methods. DNA-based technologies have emerged in recent decades as valuable tools to achieve food authentication, and advanced DNA-based methods and platforms are being developed. The present review focuses on the recent and advanced DNA-based techniques for the authentication of probiotic, PDO and PGI fermented foods and beverages. Moreover, the most promising DNA-based detection tools are presented. Strain- and species-specific DNA-based markers of microorganisms used as starter cultures or (probiotic) adjuncts for the production of probiotic and fermented food and beverages have been exploited for valuable authentication in several detection methods. Among the available technologies, propidium monoazide (PMA) real-time polymerase chain reaction (PCR)-based technologies allow for the on-time quantitative detection of viable microbes. DNA-based lab-on-a-chips are promising devices that can be used for the on-site and on-time quantitative detection of microorganisms. PCR-DGGE and metagenomics, even combined with the use of PMA, are valuable tools allowing for the fingerprinting of the microbial communities, which characterize PDO and PGI fermented foods and beverages, and they are necessary for authentication besides permitting the detection of extra or mislabeled species in probiotic products. These methods, in relation to the authentication of probiotic foods and beverages, need to be used in combination with PMA, culturomics or flow cytometry to allow for the enumeration of viable microorganisms.

Genetic basis for probiotic yeast phenotypes revealed by nanopore sequencing

Probiotic yeasts are emerging as preventative and therapeutic solutions for disease. Often ingested via cultured foods and beverages, they can survive the harsh conditions of the gastrointestinal tract and adhere to it, where they provide nutrients and inhibit pathogens like Candida albicans. Yet, little is known of the genomic determinants of these beneficial traits. To this end, we have sequenced 2 food-derived probiotic yeast isolates that mitigate fungal infections. We find that the first strain, KTP, is a strain of Saccharomyces cerevisiae within a small clade that lacks any apparent ancestry from common European/wine S. cerevisiae strains. Significantly, we show that S. cerevisiae KTP genes involved in general stress, pH tolerance, and adherence are markedly different from S. cerevisiae S288C but are similar to the commercial probiotic yeast species S. boulardii. This suggests that even though S. cerevisiae KTP and S. boulardii are from different clades, they may achieve probiotic effect through similar genetic mechanisms. We find that the second strain, ApC, is a strain of Issatchenkia occidentalis, one of the few of this family of yeasts to be sequenced. Because of the dissimilarity of its genome structure and gene organization, we infer that I. occidentalis ApC likely achieves a probiotic effect through a different mechanism than the Saccharomyces strains. Therefore, this work establishes a strong genetic link among probiotic Saccharomycetes, advances the genomics of Issatchenkia yeasts, and indicates that probiotic activity is not monophyletic and complimentary mixtures of probiotics could enhance health benefits beyond a single species.

In Vivo Toxicity Assessment of the Probiotic Bacillus amyloliquefaciens HTI-19 Isolated from Stingless Bee (Heterotrigona itama) Honey

This study evaluated the acute and sub-acute toxicity of B. amyloliquefaciens HTI-19 (isolated from stingless bee honey) in female Sprague Dawley rats. In an acute toxicity study, the rats received a low dosage (1 × 10⁹ CFU·mL^-1), medium dosage (3 × 10⁹ CFU·mL^-1), or high dosage (1 × 10¹⁰ CFU·mL^-1) of B. amyloliquefaciens HTI-19 daily orally by syringe-feeding for 14 days. For the subacute toxicity study, rats received a low dosage (1 × 10⁹ CFU·mL^-1) or a high dosage (1 × 10¹⁰ CFU·mL^-1) for 28 days. The probiotic feeding in acute and sub-acute toxicity studies showed no mortality or significant abnormalities in rats throughout the experimental period. In week 2 of the acute study, the body weight of the rats showed a significant increase (p < 0.05) compared to the control. By gross and microscopic examination of organs, no evidently significant changes were observed in the morphology of organs. Serum biochemical tests and blood hematology tests also revealed no treatment-related changes. Overall, these data indicated that oral administration of B. amyloliquefaciens HTI-19 up to 1 × 10⁹ CFU·mL^-1 for 28 days can be considered safe.

Microbiological Testing of Probiotic Preparations

Probiotic microorganisms that are potentially beneficial to the health of the host are commercially available in a great variety of products. Not all microorganism strains present in products have proven beneficial to the health properties. These products include not only foodstuffs but also dietary supplements, food for special medical purposes, medicinal products, as well as cosmetics and medical devices. These products contain from one to a dozen bacterial strains of the same or different species and sometimes also fungal strains. Since the pro-health effects of probiotics depend on a specific strain, the number of its cells in a dose, and the lack of pathogenic microorganisms, it is extremely important to control the quality of probiotics. Depending on the classification of a given product, its form, and its content of microorganisms, the correct determination of the number of microorganisms and their identification is crucial. This article describes the culture-dependent and culture-independent methods for testing the contents of probiotic microorganisms, in addition to biochemical and genetic methods of identification. The microbiological purity requirements for various product categories are also presented. Due to numerous reports on the low quality of probiotic products available on the market, it is important to standardise research methods for this group of products and to increase the frequency of inspections of these products.

Genotyping of Probiotic Lactobacilli in Nigerian Fermented Condiments for Improved Food Safety

BACKGROUND: Plant-based naturally fermented condiments usually result in poor quality products with various bacteria and fungi contaminants. Previous reports suggested the use of starter cultures from previously fermented condiments in fermentation processes to ensure health-promoting benefits, improved quality, shelf life, and organoleptic properties for the achievement of healthy nutrition, safe, and quality food. AIM: This study aimed to genotype potential lactobacilli from locally fermented condiments for improved food safety. METHODS: The lactobacilli colonies isolated from fermented condiments purchased from food markets in Southwest Nigeria were profiled for probiotic activities, hemolytic activities, antibiotics susceptibility, and inhibitory activities against food pathogens. Interesting probiotic lactobacilli were identified using 16S rRNA gene sequencing and evaluated for phylogenetic relatedness with other globally reported probiotic lactobacilli. RESULTS: Lactobacillus species which expressed significant probiotics, γ-hemolysis, anti-spoilage, and anti-listerial activities (P < 0.05) with tolerable safety profiles were identified as Lactiplantibacillus plajomi YD001 (MW280136), Lactiplantibacillus plantarum YD002 (MW280139), L. plantarum YD003 (MW280137), and Lacticaseibacillus paracasei YD004 (MW280138) possessed 50.75, 50.61, 50.75, and 52.54 mol% DNA G+C contents, respectively. The species clustered into different phylogroups with high clonal relatedness with other potential lactobacilli meta-data (≥96.80%) obtained from the public repository. CONCLUSION: Obtained genotyped Lactobacillus species are potential starter cultures for improved fermentation processes, control of food pathogens, and spoilage organisms.

Therapeutic Anti-Depressant Potential of Microbial GABA Produced by Lactobacillus rhamnosus Strains for GABAergic Signaling Restoration and Inhibition of Addiction-Induced HPA Axis Hyperactivity

The role of the microbiota–gut–brain (MGB) axis in mood regulation and depression treatment has gained attention in recent years, as evidenced by the growing number of animal and human studies that have reported the anti-depressive and associated gamma-aminobutyric acid-ergic (GABAergic) effects of probiotics developed from Lactobacillus rhamnosus bacterial strains in the gut microbiome. The depressive states attenuated by these probiotics in patients suffering from clinical depression also characterize the severe and relapse-inducing withdrawal phase of the addiction cycle, which has been found to arise from the intoxication-enabled hyperregulation of the hypothalamic–pituitary–adrenal (HPA) axis, the body’s major stress response system, and a corresponding attenuation of its main inhibitory system, the gamma-aminobutyric acid (GABA) signaling system. Therefore, the use of probiotics in the treatment of general cases of depression provides hope for a novel therapeutic approach to withdrawal depression remediation. This review discusses potential therapeutic avenues by which probiotic application of Lactobacillus rhamnosus strains can be used to restore the central GABAergic activity responsible for attenuating the depression-inducing HPA axis hyperactivity in addiction withdrawal. Also, information is provided on brain GABAergic signaling from other known GABA-producing strains of gut microbiota.

Compositional Quality and Possible Gastrointestinal Performance of Marketed Probiotic Supplements

The local pharmacies and shops are brimming with various probiotic products that herald a range of health benefits. The poor quality of probiotic products in both dosage and species is symptomatic of this multi-billion-dollar market making it difficult for consumers to single out reliable ones. This study aims to fill the potential gap in the labeling accuracy of probiotic products intended for human consumption. We describe a combinatorial approach using classical culture-dependent technique to quantify and molecular techniques (16 s rRNA gene sequencing, multilocus sequence, and ribotyping) for strain recognition of the microbial contents. The full gamut of probiotic characteristics including acid, bile and lysozyme tolerances, adhesiveness, anti-pathogenicity, and degree of safeness were performed. Their capacity to endure gastro-intestinal (GIT) stresses and select drugs was assessed in vitro. Our results forced us to declare that the local probiotic market is essentially unregulated. Almost none of the probiotic products tested met the label claim. Some (11%) have no viable cells, and a quarter (27%) showing significant inter-batch variation. A lower microbial count was typical with undesirables constituting a quarter of the total (~ 27%). Half of the products contained antibiotic-resistant strains; the unregulated use of these probiotics carries the risk of spreading antibiotic resistance to gut pathobionts. Poor tolerance to gut conditions and mediocre functionalism make the case worse. The current regulatory systems do not take this discrepancy into account. We recommend an evidence-based regular market surveillance of marketed probiotics to ensure the authenticity of the claims and product effectiveness.

Characterization and Viability Prediction of Commercial Probiotic Supplements under Temperature and Concentration Conditioning Factors by NIR Spectroscopy

The quality of probiotics has been associated with bacteria and yeast strains’ contents and their stability against conditioning factors. Near-infrared spectroscopy (NIRS), as a non-destructive, fast, real-time, and cost-effective analytical technique, can provide some advantages over more traditional food quality control methods in quality evaluation. The aim of our study was to evaluate the applicability of NIRS to the characterization and viability prediction of three commercial probiotic food supplement powders containing lactic acid bacteria (LAB) subjected to concentration and temperature conditioning factors. For each probiotic, 3 different concentrations were considered, and besides normal preparation (25 °C, control), samples were subjected to heat treatment at 60 or 90 °C and left to cool down until reaching room temperature prior to further analysis. Overall, after applying chemometrics to the NIR spectra, the obtained principal component analysis-based linear discriminant analysis (PCA-LDA) classification models showed a high accuracy in both recognition and prediction. The temperature has an important impact on the discrimination of samples. According to the concentration, the best models were identified for the 90 °C temperature treatment, reaching 100% average correct classification for recognition and over 90% for prediction. However, the prediction accuracy decreased substantially at lower temperatures. For the 25°C temperature treatment, the prediction accuracy decreased to nearly 60% for 2 of the 3 probiotics. Moreover, according to the temperature level, both the recognition and prediction accuracies were close to 100%. Additionally, the partial least square regression (PLSR) model achieved respectable values for the prediction of the colony-forming units (log CFU/g) of the probiotic samples, with a determination coefficient for prediction (R2Pr) of 0.82 and root mean square error for prediction (RMSEP) of 0.64. The results of our study show that NIRS is a fast, reliable, and promising alternative to the conventional microbiology technique for the characterization and prediction of the viability of probiotic supplement drink preparations.

Microbiological Quality and Resistance to an Artificial Gut Environment of Two Probiotic Formulations

The quality control of probiotic products is the focus of numerous organizations worldwide. Several studies have highlighted the poor microbiological quality of many commercial probiotic formulations in terms of the identity of the contained microorganisms, viability, and purity, thus precluding the expected health benefits and representing a potential health risk for consumers. In this paper, we analyzed the contents of two probiotic formulations, one composed of an encapsulated mixture of lactobacilli and bifidobacteria, and one by a lyophilized yeast. The microorganisms contained in the products were quantified and identified using up-to-date methodologies, such as MALDI-TOF MS and metagenomic analysis. Moreover, as acid and bile tolerance is included among the criteria used to select probiotic microorganisms, in vitro tests were performed to evaluate the behavior of the formulations in conditions mimicking the harsh gastric environment and the intestinal fluids. Our results indicate the high quality of the formulations in terms of the enumeration and identification of the contained organisms, as well as the absence of contaminants. Moreover, both products tolerated the acidic conditions well, with encapsulation providing further protection for the microorganisms. A good tolerance to the simulated artificial intestinal conditions was also evidenced for both preparations.

Fermented pomegranate extracts protect against oxidative stress and aging of skin

BACKGROUND

Punica granatum (pomegranate) potentially ameliorates skin inflammation and pain, including herpetic stromal keratitis. Fermentation is a biotechnological technique that may naturally induce health benefits by producing antioxidants. However, the anti-aging effect of fermented pomegranate extracts (FPE) on the skin is still unclear.

AIM

This investigation evaluates the effects of fermented pomegranate as a functional supplement (FPE drink, FPE-D) and a cosmetic ingredient (FPE serum, FPE-S) in vitro and in vivo.

PATIENTS/METHODS

The effects of FPE products for anti-oxidation, anti-tyrosinase, anti-inflammation, and anti-aging were examined. Forty subjects were randomly allocated to FPE-D or placebo drink groups (50 ml of a FPE-D /placebo drink daily for 8 weeks for each subject), and another 40 subjects were recruited to FPE-S or placebo serum groups (about 3 ml of a FPE-S /placebo serum daily and nightly/daily for 4 weeks for each subject) in a double-blind study.

RESULTS

The effects of FPE products on the DPPH, ABTS⁺ , and NO· free radical scavenging activities, their inhibiting of tyrosinase activity and their enhancement of the skin health of healthy subjects, were investigated. FPE-D improved the moisture, brightness, elasticity, and collagen density of the skin of most subjects at 8 weeks relative to the baseline without treatment (p < 0.05). After 4 weeks of FPE-S serum consumption, the moisture, brightness, elasticity, spots, UV spots, and collagen density of skin were slightly better than those at week 0 (p < 0.05).

CONCLUSIONS

The daily consumption of fermented pomegranate extracts can protect the skin against oxidative stress and slow skin aging.

Evaluation of Dietary Supplements Containing Viable Bacteria by Cultivation/MALDI-TOF Mass Spectrometry and PCR Identification

The insufficient quality of products containing beneficial live bacteria in terms of content and viability of labelled microorganisms is an often-reported problem. The aim of this work was to evaluate the quality of dietary supplements containing viable bacteria available in Slovenian pharmacies using plate counting, matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and species- or subspecies-specific PCR with DNA isolated from consortia of viable bacteria, from individual isolates, or directly from the products. Twelve percent of the products (3 of 26) contained insufficient numbers of viable bacteria. Eighty-three of the labelled species (111 in total) were confirmed by PCR with DNA from the product; 74% of these were confirmed by PCR with DNA from viable consortium, and 65% of these were confirmed by MALDI-TOF MS analysis of colonies. Certain species in multi-strain products were confirmed by PCR with DNA from viable consortia but not by MALDI-TOF MS, suggesting that the number of isolates examined (three per labelled strain) was too low. With the exception of Lacticaseibacillus casei and closely related species (Lacticaseibacillus rhamnosus and Lacticaseibacillus zeae), PCR and MALDI-TOF identification results agreed for 99% of the isolates examined, although several MALDI-TOF results had lower score values (1.700-1.999), indicating that the species identification was not reliable. The species L. zeae, which appeared in 20 matches of the Biotyper analysis, was identified as L. rhamnosus by PCR. The MALDI-TOF MS analysis was also unsuccessful in detecting Lactobacillus acidophilus La-5 and Bacillus coagulans due to missing peaks and unreliable identification, respectively. Mislabelling was detected by both methods for two putative L. casei strains that turned out to belong to the species Lacticaseibacillus paracasei. PCR remains more successful in subspecies-level identification as long as the database of MALDI-TOF MS spectra is not expanded by building in-house databases. The lack of positive PCR results with viable consortia or colonies, but positive PCR results with DNA isolated directly from the products observed in 10% (11/112) of the labelled strains, suggests the presence of non-culturable bacteria in the products. MALDI-TOF MS is a faster and simpler alternative to PCR identification, provided that a sufficient number of colonies are examined. Generation of in-house library may further improve the identification accuracy at the species and sub-species level.

The role of the microbiome in gastrointestinal inflammation

The microbiome plays an important role in maintaining human health. Despite multiple factors being attributed to the shaping of the human microbiome, extrinsic factors such diet and use of medications including antibiotics appear to dominate. Mucosal surfaces, particularly in the gut, are highly adapted to be able to tolerate a large population of microorganisms whilst still being able to produce a rapid and effective immune response against infection. The intestinal microbiome is not functionally independent from the host mucosa and can, through presentation of microbe-associated molecular patterns (MAMPs) and generation of microbe-derived metabolites, fundamentally influence mucosal barrier integrity and modulate host immunity. In a healthy gut there is an abundance of beneficial bacteria that help to preserve intestinal homoeostasis, promote protective immune responses, and limit excessive inflammation. The importance of the microbiome is further highlighted during dysbiosis where a loss of this finely balanced microbial population can lead to mucosal barrier dysfunction, aberrant immune responses, and chronic inflammation that increases the risk of disease development. Improvements in our understanding of the microbiome are providing opportunities to harness members of a healthy microbiota to help reverse dysbiosis, reduce inflammation, and ultimately prevent disease progression.

Targeted Delivery of Probiotics: Perspectives on Research and Commercialization

Considering the significance of the gut microbiota on human health, there has been ever-growing research and commercial interest in various aspects of probiotic functional foods and drugs. A probiotic food requires cautious consideration in terms of strain selection, appropriate process and storage conditions, cell viability and functionality, and effective delivery at the targeted site. To address these challenges, several technologies have been explored and some of them have been adopted for industrial applicability. Encapsulation of probiotics has been recognized as an effective way to stabilize them in their dried form. By conferring a physical barrier to protect them from adverse conditions, the encapsulation approach renders direct benefits on stability, delivery, and functionality. Various techniques have been explored to encapsulate probiotics, but it is noteworthy that the encapsulation method itself influences surface morphology, viability, and survivability of probiotics. This review focuses on the need to encapsulate probiotics, trends in various encapsulation techniques, current research and challenges in targeted delivery, the market status of encapsulated probiotics, and future directions. Specific focus has been given on various in vitro methods that have been explored to better understand their delivery and performance.

Authenticity of probiotic foods and dietary supplements: A pivotal issue to address

The market of probiotic foods and supplements is growing rapidly but frequently the commercialized products are not compliant with their labels in terms of claimed probiotic strain(s) and labeled number of viable probiotic cells, thus mining the authenticity of these probiotic products.In this review, we provide an up-to-date overview of: (i) the current regulatory aspects, (ii) the consistency of probiotic foods and supplements with their labels, (iii) the implications of mislabeling on the quality, safety and functionality of these products and (iv) the available and most promising methods to assess the authenticity of these products, taking into account the need to discriminate among the different physiological states probiotics might be in the carrier matrices. It arises that authenticity of probiotic foods and supplements is an urgent issue, of industrial and legislation relevance, that need to be addressed. A plethora of methods are available to reach this goal, each with its own advantages and disadvantages. Protocols that combine the use of propidium monoazide (PMA) with metagenomics or polyphasic approaches including the PMA real time PCR or flow cytometry (for the viability assessment) and the whole genome sequence analysis (for the identification and typing of the probiotic strain) are the most promising that should be standardized and used by producers and regulators.

Psychobiotic Effects of Multi-Strain Probiotics Originated from Thai Fermented Foods in a Rat Model

This work aimed to investigate the psychobiotic effects of six bacterial strains on the mind and behavior of male Wistar rats. The probiotic (PRO) group (n=7) were rats pre-treated with antibiotics for 7 days followed by 14-day probiotic administration, antibiotics (ANT) group (n=7) were rats treated with antibiotics for 21 days without probiotics. The control (CON) group (n=7) were rats that received sham treatment for 21 days. The six bacterial strains with probiotic properties were mostly isolated from Thai fermented foods; Pedicoccus pentosaceus WS11, Lactobacillus plantarum SK321, L. fermentum SK324, L. brevis TRBC 3003, Bifidobacterium adolescentis TBRC 7154 and Lactococcus lactis subsp. lactis TBRC 375. The probiotics were freeze-dried into powder (6×109 CFU/5 g) and administered to the PRO group via oral gavage. Behavioral tests were performed. The PRO group displayed significantly reduced anxiety level and increased locomotor function using a marble burying test and open field test, respectively and significantly improved short-term memory performance using a novel object recognition test. Antibiotics significantly reduced microbial counts in rat feces in the ANT group by 100 fold compared to the PRO group. Probiotics significantly enhanced antioxidant enzymatic and non-enzymatic defenses in rat brains as assessed using catalase activity and ferric reducing antioxidant power assay, respectively. Probiotics also showed neuroprotective effects with less pyknotic cells and lower frequency of vacuolization in cerebral cortex. This multi-strain probiotic formulation from Thai fermented foods may offer a potential to develop psychobiotic-rich functional foods to modulate human mind and behaviors.

Characterization of Lactic Acid Bacteria in Raw Buffalo Milk: a Screening for Novel Probiotic Candidates and Their Transcriptional Response to Acid Stress

Lactic acid bacteria (LAB) are important microorganisms for the food industry due to their functional activity, as starters and potential probiotic strains. With that in mind, we explored the LAB diversity in raw buffalo milk, screening for novel potential probiotic strains. A total of 11 strains were identified by combination of MALDI-TOF and partial 16S rDNA sequencing and selected as potential probiotic candidates. Bacteria innocuity assessment was performed by determining antimicrobial susceptibility and the presence of virulence factors. Antagonism activity against Escherichia coli, Pseudomonas aeruginosa, Listeria monocytogenes and Staphylococcus aureus was assessed, as well as milk proteolytic activity and exopolysaccharides production. Seven strains were identified as innocuous and two of them, Lactobacillus rhamnosus LB1.5 and Lactobacillus paracasei LB6.4 were selected for further probiotic potential analyses. Both strains demonstrated adhesion ability to Caco-2 cells, coaggregated with S. aureus and E. coli and maintained cell viability after gastrointestinal simulation in vitro, suggesting their probiotic potential. Furthermore, the transcriptional response of Lact. rhamnosus LB1.5 and Lact. paracasei LB6.4 to in vitro acid stress was assessed by RT-qPCR targeting seven genes related to adhesion, aggregation, stress tolerance, DNA repair and central metabolism. The association between the transcriptional responses and the maintenance of cell viability after gastrointestinal simulation highlights the genetic ability as probiotic of the two selected strains. Finally, we have concluded that Lact. rhamnosus LB1.5 and Lact. paracasei LB6.4 are important probiotic candidates to further in vivo studies.

Molecular Routes to Specific Identification of the Lactobacillus Casei Group at the Species, Subspecies and Strain Level

The genus Lactobacillus includes, among others, Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus, species that are collectively referred to as the Lactobacillus casei group. Many studies have shown that strains belonging to this group may decrease lactose intolerance, the effects of inflammatory bowel disease, diarrhea, constipation, food allergies and even colon cancer. Moreover, evidences exists of positive effects of these bacteria on mucosal immunity and blood cholesterol level. Because of their beneficial influence on human health, many of them are used as food additives and probiotic pharmaceuticals. It should be stressed that health-promoting properties are not attributed at the species level, but to specific strains. Therefore, procedures are necessary to allow specific identification at each phylogenetic level-genus, species and strain. In this paper we present a practical overview of molecular methods for the identification and differentiation of L. casei bacteria. The research included 30 bacterial strains belonging to three species: L.casei, L. paracasei and L. rhamnosus. Among the tested procedures were genus- and species-specific PCR, multiplex-PCR, Real-Time HRM analysis, RFLP-PCR, rep-PCR, RAPD-PCR, AFLP-PCR, and proteomic methods such as MALDI-TOF MS typing and SDS-PAGE fingerprinting. The obtained results showed that multiplex-PCR and MALDI-TOF MS turned out to be the most useful methods to identify the tested bacteria at the species level. At the strain level, the AFLP-PCR method showed the highest discriminatory power. We hope that the presented results will allow for the easy selection of an appropriate procedure, depending on the experiment conducted and the equipment capabilities of any given laboratory.

Identification and Growth Characterization of a Novel Strain of Saccharomyces boulardii Isolated From Soya Paste

The nonpathogenic yeast Saccharomyces boulardii (Sb) has beneficial effects on the human intestine, and thus has been prescribed as probiotics for the treatment of diarrhea and gastrointestinal diseases. This is the only commercialized yeast with the purpose of being used as human medicine. Currently, little is known about their multiple mechanisms of actions. The S. boulardii yeast strain is isolated and identified by using the BIOLOG^TM microarray identification system and morphologically. To understand its functional roles, the present study investigates the ability of this yeast to tolerate different concentrations of bile salt up to 2.5%, cell hydrophobicity, antioxidants, autoaggregation activity, and simulated gastrointestinal digestion. The effect of temperatures (up to 50°C), pH (up to 8.0), and salinity (at best 7%) was also monitored on the growth and survival of the yeast cell. The physicochemical analyses revealed that S. boulardii could survive in stomach conditions at pH 2.5, temperature 37°C, and 2% bile salt. Antibiotic susceptibility of S. boulardii was carried out using commercial antibiotic discs. The antimicrobial activity of the isolated S. boulardii against bacterial pathogens related to diarrhea diseases was in-vitro determined by the Well Diffusion method. The biosafety assay findings also claimed S. boulardii could be a potential probiotic. The experimental findings suggest that the isolated S. boulardii possesses excellent probiotic capacities as a biotherapeutic agent for antidiarrheal and gastrointestinal disorders.