Media for the isolation and enumeration of bifidobacteria in dairy products

Bifidobacterium pseudocatenulatum In Vitro In Vivo

The genus Bifidobacterium has been widely used in functional foods for health promotion due to its beneficial effects on human health, especially in the gastrointestinal tract (GIT). In this study, we characterize the anti-inflammatory potential of the probiotic strain Bifidobacterium pseudocatenulatum G7, isolated from a healthy male adult. G7 secretion inhibited inflammatory response in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Moreover, oral administration of bacteria G7 alleviated the severity of colonic inflammation in dextran sulfate sodium (DSS)-treated colitis mice, which was evidenced by a decreased disease activity index (DAI) and enhanced structural integrity of the colon. The 16S rRNA gene sequencing result illustrated that the G7 alleviated DSS-induced gut microbiota dysbiosis, accompanied by the modulated bile acids and short-chain fatty acid (SCFA) levels. Overall, our results demonstrated the potential anti-inflammatory effects of Bifidobacterium pseudocatenulatum G7 on both in vitro and in vivo models, which provided a solid foundation for further development of a novel anti-inflammatory probiotic.

Drying of probiotics to enhance the viability during preparation, storage, food application, and digestion: A review

Functional food products containing viable probiotics have become increasingly popular and demand for probiotic ingredients that maintain viability and stability during processing, storage, and gastrointestinal digestions. This has resulted in heightened research and development of powdered probiotic ingredients. The aim of this review is to overview the development of dried probiotics from upstream identification to downstream applications in food. Free probiotic bacteria are susceptible to various environmental stresses during food processing, storage, and after ingestion, necessitating additional materials and processes to preserve their activity for delivery to the colon. Various classic and emerging thermal and nonthermal drying technologies are discussed for their efficiency in preparing dehydrated probiotics, and strategies for enhancing probiotic survival after dehydration are highlighted. Both the formulation and drying technology can influence the microbiological and physical properties of powdered probiotics that are to be characterized comprehensively with various techniques. Furthermore, quality control during probiotic manufacturing and strategies of incorporating powdered probiotics into liquid and solid food products are discussed. As emerging technologies, structure-design principles to encapsulate probiotics in engineered structures and protective materials with improved survivability are highlighted. Overall, this review provides insights into formulations and drying technologies required to supplement viable and stable probiotics into functional foods, ensuring the retention of their health benefits upon consumption.

Bifidobacterium mechanisms of immune modulation and tolerance

Bifidobacterium is a widely distributed commensal bacterial genus that displays beneficial pro-homeostatic and anti-inflammatory immunomodulatory properties. Depletion or absence of Bifidobacterium in humans and model organisms is associated with autoimmune responses and impaired immune homeostasis. At the cellular level, Bifidobacterium upregulates suppressive regulatory T cells, maintains intestinal barrier function, modulates dendritic cell and macrophage activity, and dampens intestinal Th2 and Th17 programs. While there has been a large volume of literature characterizing the probiotic properties of various Bifidobacterial species, the likely multifactorial mechanisms underlying these effects remain elusive, in particular, its immune tolerogenic effect. However, recent work has shed light on Bifidobacterium surface structural polysaccharide and protein elements, as well as its metabolic products, as commensal mediators of immune homeostasis. This review aims to discuss several mechanisms Bifidobacterium utilizes for immune modulation as well as their indirect impact on the regulation of gut microbiome structure and function, from structural molecules to produced metabolites. These mechanisms are pertinent to an increasingly networked understanding of immune tolerance and homeostasis in health and disease.

Acetate modulates the inhibitory effect of Lactobacillus gasseri against the pathogenic yeasts Candida albicans and Candida glabrata

The exploration of the interference prompted by commensal bacteria over fungal pathogens is an interesting alternative to develop new therapies. In this work we scrutinized how the presence of the poorly studied vaginal species Lactobacillus gasseri affects relevant pathophysiological traits of Candida albicans and Candida glabrata. L. gasseri was found to form mixed biofilms with C. albicans and C. glabrata resulting in pronounced death of the yeast cells, while bacterial viability was not affected. Reduced viability of the two yeasts was also observed upon co-cultivation with L. gasseri under planktonic conditions. Either in planktonic cultures or in biofilms, the anti-Candida effect of L. gasseri was augmented by acetate in a concentration-dependent manner. During planktonic co-cultivation the two Candida species counteracted the acidification prompted by L. gasseri thus impacting the balance between dissociated and undissociated organic acids. This feature couldn't be phenocopied in single-cultures of L. gasseri resulting in a broth enriched in acetic acid, while in the co-culture the non-toxic acetate prevailed. Altogether the results herein described advance the design of new anti-Candida therapies based on probiotics, in particular, those based on vaginal lactobacilli species, helping to reduce the significant burden that infections caused by Candida have today in human health.

Administration of Bifidobacterium pseudolongum suppresses the increase of colonic serotonin and alleviates symptoms in dextran sodium sulfate-induced colitis in mice

Previous studies suggested that altered gut serotonin (5-HT) signaling is implicated in the pathophysiology of inflammatory bowel disease (IBD). Indeed, 5-HT administration reportedly exacerbated the severity of murine dextran sodium sulfate (DSS)-induced colitis that mimics human IBD. Our recent study suggested that Bifidobacterium pseudolongum, one of the most predominant bifidobacterial species in various mammals, reduces the colonic 5-HT content in mice. The present study thus tested whether the administration of B. pseudolongum prevents DSS-induced colitis in mice. Colitis was induced by administering 3% DSS in drinking water in female BALB/c mice, and B. pseudolongum (10⁹ CFU/day) or 5-aminosalicylic acid (5-ASA, 200 mg/kg body weight) was intragastrically administered once daily throughout the experimental period. B. pseudolongum administration reduced body weight loss, diarrhea, fecal bleeding, colon shortening, spleen enlargement, and colon tissue damage and increased colonic mRNA levels of cytokine genes (Il1b, Il6, Il10, and Tnf) almost to an extent similar to 5-ASA administration in DSS-treated mice. B. pseudolongum administration also reduced the increase of colonic 5-HT content, whereas it did not alter the colonic mRNA levels of genes that encode the 5-HT synthesizing enzyme, 5-HT reuptake transporter, 5-HT metabolizing enzyme, and tight junction-associated proteins. We propose that B. pseudolongum is as beneficial against murine DSS-induced colitis as the widely used anti-inflammatory agent 5-ASA. However, further studies are needed to clarify the causal relationship between the reduced colonic 5-HT content and reduced severity of DSS-induced colitis caused by B. pseudolongum administration.

The Pleiotropic Effects of Carbohydrate-Mediated Growth Rate Modifications in Bifidobacterium longum NCC 2705

Bifidobacteria are saccharolytic bacteria that are able to metabolize a relatively large range of carbohydrates through their unique central carbon metabolism known as the “bifid-shunt”. Carbohydrates have been shown to modulate the growth rate of bifidobacteria, but unlike for other genera (e.g., E. coli or L. lactis), the impact it may have on the overall physiology of the bacteria has not been studied in detail to date. Using glucose and galactose as model substrates in Bifidobacterium longum NCC 2705, we established that the strain displayed fast and slow growth rates on those carbohydrates, respectively. We show that these differential growth conditions are accompanied by global transcriptional changes and adjustments of central carbon fluxes. In addition, when grown on galactose, NCC 2705 cells were significantly smaller, exhibited an expanded capacity to import and metabolized different sugars and displayed an increased acid-stress resistance, a phenotypic signature associated with generalized fitness. We predict that part of the observed adaptation is regulated by the previously described bifidobacterial global transcriptional regulator AraQ, which we propose to reflect a catabolite-repression-like response in B. longum. With this manuscript, we demonstrate that not only growth rate but also various physiological characteristics of B. longum NCC 2705 are responsive to the carbon source used for growth, which is relevant in the context of its lifestyle in the human infant gut where galactose-containing oligosaccharides are prominent.

Integration of Corn and Cane for Ethanol Production: Effects of Lactobacilli Contamination on Fermentative Parameters and Use of Ionizing Radiation Treatment for Disinfection

Recently, in Brazil, corn ethanol industries are being installed and the integration with sugar/energy-cane has been proposed, using bagasse for cogeneration and the juice to dilute the corn. However, this integration may have some limitations, such as the quality of the cane juice and potential contamination by microorganisms brought with the cane from the field. In this article, we first tested the effects of mixing energy cane juice with corn on fermentative parameters. We also assessed the effects of Lactobacilli. contamination on organic acids produced during the fermentation and fermentation parameters and proposed the use of ionizing radiation to replace antibiotics as a disinfection control method. Our results showed that mixing energy cane juice with corn does not have any negative effect on fermentation parameters, including ethanol production. The contamination with Lactobacilli. considerably increased the production of acetic, lactic, and succinic acid, reducing the pH and ethanol content from 89.2 g L−1 in the sterilized treatment to 72.9 g L−1 in the contaminated treatment. Therefore, for the integration between corn and cane to be applied on an industrial scale, it is essential to have effective disinfection before fermentation. Ionizing radiation (20 kGy) virtually disinfected the wort, showing itself to be a promising technology; however, an economic viability study for adopting it in the industry should be carried out.

Development of a Novel Flavored Goat Cheese with Gentiana lutea Rhizomes

Gentiana lutea rhizomes, generally used as a bittering agent in food, were harvested from two geographical sites (Massif Central: MC and Jura: J) to evaluate their potential use in the flavoring step during goat cheesemaking. Gentian flavored goat cheeses (MCGC and JGC) were elaborated by a one-night immersion of unflavored goat cheeses (CGC) into gentian-infused whey. The impregnation of gentian in goat cheeses was evaluated by chemical and sensory analysis. The chemical composition of cheeses was analyzed by HS-SPME-GC-MS (Head-Space-Solid Phase MicroExtraction-Gas Chromatography-Mass Spectrometry) for volatile compounds (alcohols, ketones, aldehydes, esters, alkenes, alkanes, acids, terpenes) and UHPLC-DAD (Ultra High-Performance Liquid Chromatography-Diode Array Detector) for gentian bitter compounds (seco-iridoids). The sensory analysis consisted of a bitterness rating and a free description of cheeses by 17 trained panelists. Results of the study highlighted that unflavored goat cheeses presented higher unpleasant notes (goaty and lactic whey) and higher amounts of hexanoic acid and toluene compared to gentian flavored goat cheeses. The bitterness of gentian flavored goat cheeses was higher compared to unflavored cheeses and could be explained by loganic acid transfer from yellow gentian to flavored cheeses. Other free descriptors of gentian flavored goat cheeses revealed more complex notes (herbal, vegetal, floral, sweet, spicy and creamy) and higher relative amounts of volatile compounds such as 3-methyl butanoic acid, 2-methyl propanoic acid, 4-methyl decane, 2,3-butanediol, ethanol, diacetyl, methyl acetate and 2-phenylethyl acetate, compared to unflavored cheeses. Phenylethyl acetate was the only volatile compound that enabled differentiation of gentian origin on gentian flavored goat cheeses. Gentian rhizomes could be considered a promising flavoring agent contributing to the olfactive and gustative complexity of flavored goat cheeses and the reduction of their goaty perceptions.

Spotlight on the Compositional Quality of Probiotic Formulations Marketed Worldwide

On the worldwide market, a great number of probiotic formulations are available to consumers as drugs, dietary supplements, and functional foods. For exerting their beneficial effects on host health, these preparations should contain a sufficient amount of the indicated living microbes and be pathogen-free to be safe. Therefore, the contained microbial species and their amount until product expiry are required to be accurately reported on the labels. While commercial formulations licensed as drugs are subjected to rigorous quality controls, less stringent regulations are generally applied to preparations categorized as dietary supplements and functional foods. Many reports indicated that the content of several probiotic formulations does not always correspond to the label claims in terms of microbial identification, number of living organisms, and purity, highlighting the requirement for more stringent quality controls by manufacturers. The main focus of this review is to provide an in-depth overview of the microbiological quality of probiotic formulations commercialized worldwide. Many incongruences in the compositional quality of some probiotic formulations available on the worldwide market were highlighted. Even if manufacturers carry at least some of the responsibility for these inconsistencies, studies that analyze probiotic products should be conducted following recommended and up-to-date methodologies.

Consumption of indigestible saccharides and administration of Bifidobacterium pseudolongum reduce mucosal serotonin in murine colonic mucosa

SCFA increase serotonin (5-hydroxytryptamine, 5-HT) synthesis and content in the colon in vitro and ex vivo, but little is known in vivo. We tested whether dietary indigestible saccharides, utilised as a substrate to produce SCFA by gut microbiota, would increase colonic 5-HT content in mice. Male C57BL/6J mice were fed a purified diet and water supplemented with 4 % (w/v) 1-kestose (KES) for 2 weeks. Colonic 5-HT content and enterochromaffin (EC) cell numbers were lower in mice supplemented with KES than those without supplementation, while monoamine oxidase A activity and mRNA levels of tryptophan hydroxylase 1 (Tph1), chromogranin A (Chga), Slc6a4 and monoamine oxidase A (Maoa) genes in the colonic mucosa, serum 5-HT concentration and total 5-HT content in the colonic contents did not differ between groups. Caecal acetate concentration and Bifidobacterium pseudolongum population were higher in KES-supplemented mice. Similar trends were observed in mice supplemented with other indigestible saccharides, that is, fructo-oligosaccharides, inulin and raffinose. Intragastric administration of live B. pseudolongum (108 colony-forming units/d) for 2 weeks reduced colonic 5-HT content and EC cell numbers. These results suggest that changes in synthesis, reuptake, catabolism and overflow of 5-HT in the colonic mucosa are not involved in the reduction of colonic 5-HT content by dietary indigestible saccharides in mice. We propose that gut microbes including B. pseudolongum could contribute to the reduction of 5-HT content in the colonic mucosa via diminishing EC cells.

Protocol to Select Bifidobacteria from Fecal and Environmental Samples

Bifidobacteria are commensal microorganisms able to colonize several ecological niches. Since their discovery, culture-dependent methods combined with the most modern next-generation sequencing techniques have contributed to shed light on the ecological, functional and genomic features of bifidobacteria, purporting them as microorganisms with probiotic traits. Thanks to their acclaimed health-promoting effects, several members of the Bifidobacterium genus have been included in a variety of functional foods and drugs. In this context, the functional relevance of bifidobacteria in the gut explains ongoing efforts to isolate novel and potentially beneficial strains. For this purpose, development of effective and selective isolation protocols in concert with knowledge on the physiological characteristics of bifidobacterial are fundamental requirements for their recovery and discovery from their natural environments, in particular from fecal samples.

Influence of probiotic adjunct cultures on the characteristics of low-fat Feta cheese

There are different methods that have been recently applied to develop a process to manufacture low-fat Feta cheese (LFC) with acceptable flavor and texture. The objective of this study was to produce LFC from skim buffalo's milk (SBM) using Streptococcus thermophilus (ST) and Lactobacillus bulgaricus (LB) as control LFC (T1) incorporated with other probiotic adjunct cultures (PAC), such as Lactobacillus casei (LBC) in T2, Bifidobacterium bifidum (BB) in T3, and Lactococcus lactis subsp. lactis (LL) in T4. The SBM was pasteurized and inoculated with 3% of starter cultures; then, 0.4% of rennet and 3% of salt were added. After coagulation, the cheese was cut, packed, and stored at 4°C. The chemical, microbiological, and sensory characteristics of LFC were monitored during 14 days of storage. The moisture, acidity, total protein (TP), salt, and fat of LFC were approximately 75.0%, 1.0%, 17.0%, 3.0%, and 1.2%, respectively, after 14 days of storage at 4°C. The viability of PAC was high (5-7 log cfu/g) at the end of storage, which makes LFC a functional product with a valuable source of probiotic. Moreover, the adjunct cultures improved (p < .05) the sensory characteristics of LFC, including the texture and flavor.

Enhancement of low-fat Feta cheese characteristics using probiotic bacteria

The objective of this study was to manufacture low-fat Feta cheese (LFC) using different types of starter cultures, such as yogurt (Y) cultures (Streptococcus thermophilus and Lactobacillus bulgaricus), bifidobacterium (B) cultures (Bifidobacterium bifidum and Bifidobacterium longum), and mixed of them (Y + B) at different rates (0.4, 0.5, and 0.6%). The Y + B cultures improved the flavor and body and texture of LFC, especially at a ratio of 0.4 + 0.6% and 0.5 + 0.5%, which is similar to the typical full-fat Feta cheese. Also, the LFC maintained a higher number of probiotics and lactic acid bacteria after 30 d of storage at a range of 5 to 7 log cfu/g.

The Effect of Bifidobacterium Bifidum Supernatant and Cell Mass on the Proliferation Potential of Rat Bone Marrow-Derived Stromal Cells

Background

Mesenchymal stem cells (MSCs) are widely used to treat various diseases, however, their proliferative potential reduces after a number of passages. It has been shown that some probiotics such as Bifidobacterium Bifidum (B. bifidum) affect the proliferation of various cell lineages. The present study aimed to investigate the effect of B. bifidum on the proliferation of rat bone marrow stromal cells (rBMSCs) and to develop a method for compensating their proliferation reduction after some passages.

Methods

The present experimental study was conducted at Tehran University of Medical Sciences, Tehran, Iran, in 2017. The stromal cells were isolated from rBMSCs and their mesenchymal properties were confirmed by osteogenic and adipogenic differentiation media and staining. B. bifidum was cultured and the B. bifidum supernatant (BS) and bacterial cell mass (BCM) were extracted. The rBMSCs were treated with different concentrations of BS and BCM. The MTT assay was performed to measure the number of viable cells in the culture. Cell proliferation was analyzed using the paired-sample t test.

Results

Cell proliferation increased as the concentration of bacteria was increased logarithmically (0, 0.1, 0.3, 0.9, 3, 9, 30 μL/mL). In comparison with BS, cells treated with BCM showed increased cell proliferation at lower concentrations. This effect was caused by removing the "de Man, Rogosa, and Sharpe" (MRS) broth medium from the BCM culture. The optimal concentration of bacteria with the most significant effect on rBMSCs proliferation was determined.

Conclusion

A significant increase in the proliferation of stromal cells was observed; confirming the stimulatory potential of probiotics (B. bifidum) on various cells. The use of products containing probiotic bacteria can increase the proliferation potential of BMSCs.

A novel pharmaceutical approach for the analytical validation of probiotic bacterial count by flow cytometry

INTRODUCTION

Flow cytometry is a powerful and sensitive technique able to characterize single cells within a heterogeneous population. Different fluorescent dyes can be combined and used together to analyze a great variety of parameters simultaneously. In particular, flow-cytometry allows to measure viability and vitality of probiotics measuring their metabolic activity, fermentation capacity, acidification potential or oxygen uptake ability (Hayouni et al., 2008). To now, plate counting is considered the gold standard in microbiological technique for probiotic enumeration. However, this approach is limited to the detection of only those viable cells which are able to proliferate and form colonies on a solid medium but is not able to recognize not cultivable bacteria and nonviable cells.

AIM

The aim of the present study was to apply The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) parameters for the validation of new analytical methods in microbiology. ICH requirements, which are commonly employed for the analysis of drugs and chemical analytes, have been here applied to live cells for the comparison between a flow-cytometric assay and the traditional plate count method for the quantification of viable probiotics bacteria.

METHODS AND RESULTS

Combining specific viability dyes such as thiazole orange (TO) and propidium iodide (PI), probiotic counts of Lactobacillus and Bifidobacterium species were carried out using a FACS Verse (BD Biosciences) cytometer. Analyses were conducted in parallel with the traditional plate count, on specific media. Raw data were analyzed using the FACSuite software (BD Biosciences) and then elaborated with the statistical software Neolicy (VWR International). Results indicated that flow cytometry provides very similar results in cell counting if compared to classical microbiology approaches, showing better performances (ICH parameters) than the traditional plate count method.

CONCLUSIONS

This work demonstrated the analytical ICH validation of probiotic counts in food supplement products using a robust flow cytometric approach able to enumerate and to assess bacteria viability with stronger results in comparison to the traditional plate count.

Bifidobacteria cell wall-derived exo-polysaccharides, lipoteichoic acids, peptidoglycans, polar lipids and proteins - their chemical structure and biological attributes

A variety of health benefits has been documented to be associated with the consumption of probiotic bacteria, namely bifidobacteria and lactobacilli. Thanks to the scientific advances in recent years we are beginning to understand the molecular mechanisms by which bacteria in general and probiotic bacteria in particular act as host physiology and immune system modulators. More recently, the focus has shifted from live bacteria towards bacteria-derived defined molecules, so called postbiotics. These molecules may represent safer alternative compared to the live bacteria while retaining the desired effects on the host. The excellent source of effector macromolecules is the bacterial envelope. It contains compounds that are pivotal in the adhesion phenomenon, provide direct bacteria-to-host signaling capacity and the associated physiological impact and immunomodulatory properties of bacteria. Here we comprehensively review the structure and biological role of Bifidobacterium surface and cell wall molecules: exopolysaccharides, cell wall polysaccharides, lipoteichoic acids, polar lipids, peptidoglycans and proteins. We discuss their involvement in direct signaling to the host cells and their described immunomodulatory effects.

Effect of ferulic acid sugar ester with high molecular mass from corn bran on proliferation of intestinal bifidobacteria in aged mice induced by D-galactose: The role of HFASE in the intestine

Our experiment was to study the effect of high molecular mass ferulic acid sugar ester (HFASE) from corn bran on proliferation of intestinal bifidobacteria in aged mice induced by D-galactose. The number of bifidobacteria in the intestine of D-galactose-induced aging mice was lower than that of normal mice. After the intragastric administration of different doses of HFASE (100, 200, and 300 mg kg^-1  day^-1 body weight) in experimental groups, the number of bifidobacteria was also higher than the aging group. The proliferation rate of bifidobacteria in the intestine of the experimental groups was fast in the first 24 days of feeding and then tended to be gentle. The H-l experimental group (100 mg/kg body weight) had the most obvious effect of the proliferation of bifidobacteria. PRACTICAL APPLICATIONS: As the by-product of corn starch processing, corn bran was usually processed into animal feed and sold at a low price. The results of this study indicated that high molecular mass corn bran ferulic acid sugar ester had the effect of promoting the proliferation of bifidobacteria in aging mice, which provided ideas for the development and application of corn bran in the food industries. It could be added as a raw material for functional foods to common foods such as yogurt, baked bread, cereals, and porridge.

Valorization of Olive By-Products as Substrates for the Cultivation of Ganoderma lucidum and Pleurotus ostreatus Mushrooms with Enhanced Functional and Prebiotic Properties

The successful management of olive by-products constitutes a major challenge due to their huge volume, high organic content, and toxicity. Olive-mill wastes (TPOMW) and olive pruning residues (OLPR) were evaluated as substrates for the cultivation of Ganoderma lucidum and Pleurotus ostreatus. Chemical composition, glucans, total phenolic content, and antioxidant activity were measured in mushrooms, and their prebiotic potential was assessed by examining their effect on the growth of four intestinal bacteria. Several substrates based on olive by-products had a positive impact on P. ostreatus mushroom production, whereas only one performed adequately for G. lucidum. Increased ratios of OLPR to wheat-straw resulted in an increase of crude protein content in P. ostreatus fruit-bodies by up to 42%, while G. lucidum mushrooms from OLPR-based substrates exhibited an up to three-fold increase in α-glucan, or a significant enhancement of β-glucan content, when compared to beech sawdust (control). The mushrooms’ FTIR spectra confirmed the qualitative/quantitative differentiation detected by standard assays. In regard to prebiotic properties, mushrooms powder supported or even enhanced growth of both Lactobacillus acidophilus and L. gasseri after 24/48 h of incubation. In contrast, a strain-specific pattern was observed in bifidobacteria; mushrooms hindered Bifidobacterium bifidum growth, whereas they supported a similar-to-glucose growth for B. longum.

Methods for culturing anaerobes from human specimen

Anaerobes represent the dominating population in the human gut microbiota and play a key role in gut homeostasis. In addition, several anaerobes are now considered as probiotics and they remain essential to several processes in the field of biotechnology. With the implementation of MALDI-TOF MS in routine laboratories, anaerobes are no longer neglected in clinical microbiology, as their identification is made easy. However, the isolation and identification of anaerobic bacteria, remains time consuming, fastidious and costly. Various strategies have been developed, from sampling to culturing human specimens, which will be discussed in this paper. Also, particular attention is paid to isolating species with special medical importance, as for contribution to the field of culturomics.

Flow cytometry: a versatile technology for specific quantification and viability assessment of micro-organisms in multistrain probiotic products

AIMS

Classical microbiology techniques are the gold standard for probiotic enumeration. However, these techniques are limited by parameters of time, specificity and incapacity to detect viable but nonculturable (VBNC) micro-organisms and nonviable cells. The aim of the study was to evaluate flow cytometry as a novel method for the specific quantification of viable and nonviable probiotics in multistrain products.

METHODS AND RESULTS

Custom polyclonal antibodies were produced against five probiotic strains from different species (Bifidobacterium bifidum R0071, Bifidobacterium longum ssp. infantis R0033, Bifidobacterium longum ssp. longum R0175, Lactobacillus helveticus R0052 and Lactobacillus rhamnosus R0011). Evaluation of specificity confirmed that all antibodies were specific at least at the subspecies level. A flow cytometry method combining specific antibodies and viability assessment with SYTO^® 24 and propidium iodide was applied to quantify these strains in three commercial products. Analyses were conducted on two flow cytometry instruments by two operators and compared with classical microbiology using selective media. Results indicated that flow cytometry provides higher cell counts than classical microbiology (P < 0·05) in 73% of cases highlighting the possible presence of VBNC. Equivalent performances (repeatability and reproducibility) were obtained for both methods.

CONCLUSIONS

This study showed that flow cytometry methods can be applied to probiotic enumeration and viability assessment. Combination with polyclonal antibodies can achieve sufficient specificity to differentiate closely related strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

Flow cytometry provides absolute and specific quantification of viable and nonviable probiotic strains in a very short time (<2 h) compared with classical techniques (>48 h), bringing efficient tools for research and development and quality control.

Selective method for identification and quantification of Bifidobacterium animalis subspecies lactis BB-12 (BB-12) from the gastrointestinal tract of healthy volunteers ingesting a combination probiotic of BB-12 and Lactobacillus rhamnosus GG

AIM

To develop a novel validated method for the isolation of Bifidobacterium animalis ssp. lactis BB-12 (BB-12) from faecal specimens and apply it to studies of BB-12 and Lactobacillus rhamnosus GG (LGG) recovered from the healthy human gastrointestinal (GI) tract.

METHODS AND RESULTS

A novel method for isolating and enumerating BB-12 was developed based on its morphologic features of growth on tetracycline-containing agar. The method identified BB-12 correctly from spiked stool close to 100% of the time as validated by PCR confirmation of identity, and resulted in 97-104% recovery of BB-12. The method was then applied in a study of the recovery of BB-12 and LGG from the GI tract of healthy humans consuming ProNutrients^® Probiotic powder sachet containing BB-12 and LGG. Viable BB-12 and LGG were recovered from stool after 21 days of probiotic ingestion compared to baseline. In contrast, no organisms were recovered 21 days after baseline in the nonsupplemented control group.

CONCLUSIONS

We demonstrated recovery of viable BB-12, using a validated novel method specific for the isolation of BB-12, and LGG from the GI tract of healthy humans who consumed the probiotic supplement.

SIGNIFICANCE AND IMPACT OF THE STUDY

This method will enable more detailed and specific studies of BB-12 in probiotic supplements, including when in combination with LGG.

Anaerobic Probiotics: The Key Microbes for Human Health

Human gastrointestinal microbiota (HGIM) incorporate a large number of microbes from different species. Anaerobic bacteria are the dominant organisms in this microbial consortium and play a crucial role in human health. In addition to their functional role as the main source of many essential metabolites for human health, they are considered as biotherapeutic agents in the regulation of different human metabolites. They are also important in the prevention and in the treatment of different physical and mental diseases. Bifidobacteria are the dominant anaerobic bacteria in HGIM and are widely used in the development of probiotic products for infants, children and adults. To develop bifidobacteria-based bioproducts, therefore, it is necessary to develop a large-scale biomass production platform based on a good understanding of the ideal medium and bioprocessing parameters for their growth and viability. In addition, high cell viability should be maintained during downstream processing and storage of probiotic cell powder or the final formulated product. In this work we review the latest information about the biology, therapeutic activities, cultivation and industrial production of bifidobacteria.

Evaluation of culture media for selective enumeration of bifidobacteria and lactic acid bacteria

The purpose of this study was to test the suitability of Transgalactosylated oligosaccharides-mupirocin lithium salt (TOS-MUP) and MRS-clindamycin-ciprofloxacin (MRS-CC) agars, along with several other culture media, for selectively enumerating bifidobacteria and lactic acid bacteria (LAB) species commonly used to make fermented milks. Pure culture suspensions of a total of 13 dairy bacteria strains, belonging to eight species and five genera, were tested for growth capability under various incubation conditions. TOS-MUP agar was successfully used for the selective enumeration of both Bifidobacterium animalis subsp. lactis BB-12 and B. breve M-16 V. MRS-CC agar showed relatively good selectivity for Lactobacillus acidophilus, however, it also promoted the growth of Lb. casei strains. For this reason, MRS-CC agar can only be used as a selective medium for the enumeration of Lb. acidophilus if Lb. casei is not present in a product at levels similar to or exceeding those of Lb. acidophilus. Unlike bifidobacteria and coccus-shaped LAB, all the lactobacilli strains involved in this work were found to grow well in MRS pH 5.4 agar incubated under anaerobiosis at 37 °C for 72 h. Therefore, this method proved to be particularly suitable for the selective enumeration of Lactobacillus spp.

Development of a growth medium suitable for exopolysaccharide production and structural characterisation by Bifidobacterium animalis ssp. lactis AD011

Exopolysaccharides (EPSs) produced by Bifidobacteria have received considerable attention due to their ability to modify the rheological and physicochemical properties of dairy products. However, the quantification and characterisation of Bifidobacterial EPS are hampered by the presence of EPS-equivalent (EPS-E) substances in complex media such as Reinforced Clostridial Medium (RCM). This study has developed a medium based on RCM which both supports the growth of Bifidobacterium animalis ssp. lactis AD011 and does not interfere with the quantification and characterisation of the EPS generated. Medium development involved the identification of EPE-E containing components via NMR analysis followed by their removal, substitution or pre-treatment. Both beef extract and casein acid hydrolysate required chemical pre-treatment to remove polysaccharide components before the medium was free of EPS-E materials. Once EPS-E free components had been identified, lactose, glucose and galactose were evaluated as potential carbon sources. Glucose was found to be the optimum carbon source. The final medium composition supported growth to the same extent as RCM providing significant EPS yields and no interferences during analysis.

Advantageous direct quantification of viable closely related probiotics in petit-suisse cheeses under in vitro gastrointestinal conditions by Propidium Monoazide--qPCR

Species-specific Quantitative Real Time PCR (qPCR) alone and combined with the use of propidium monoazide (PMA) were used along with the plate count method to evaluate the survival of the probiotic strains Lactobacillus acidophilus La-5 and Bifidobacterium animalis subsp. lactis Bb-12, and the bacteriocinogenic and potentially probiotic strain Lactobacillus sakei subsp. sakei 2a in synbiotic (F1) and probiotic (F2) petit-suisse cheeses exposed throughout shelf-life to in vitro simulated gastrointestinal tract conditions. The three strains studied showed a reduction in their viability after the 6 h assay. Bb-12 displayed the highest survival capacity, above 72.6 and 74.6% of the initial populations, respectively, by plate count and PMA-qPCR, maintaining population levels in the range or above 6 log CFU/g. The prebiotic mix of inulin and FOS did not offer any additional protection for the strains against the simulated gastrointestinal environment. The microorganisms' populations were comparable among the three methods at the initial time of the assay, confirming the presence of mainly viable and culturable cells. However, with the intensification of the stress induced throughout the various stages of the in vitro test, the differences among the methods increased. The qPCR was not a reliable enumeration method for the quantification of intact bacterial populations, mixed with large numbers of injured and dead bacteria, as confirmed by the scanning electron microscopy results. Furthermore, bacteria plate counts were much lower (P<0.05) than with the PMA-qPCR method, suggesting the accumulation of stressed or dead microorganisms unable to form colonies. The use of PMA overcame the qPCR inability to differentiate between dead and alive cells. The combination of PMA and species-specific qPCR in this study allowed a quick and unequivocal way of enumeration of viable closely related species incorporated into probiotic and synbiotic petit-suisse cheeses and under stress conditions.

Microbial characterization of probiotics--advisory report of the Working Group "8651 Probiotics" of the Belgian Superior Health Council (SHC)

When ingested in sufficient numbers, probiotics are expected to confer one or more proven health benefits on the consumer. Theoretically, the effectiveness of a probiotic food product is the sum of its microbial quality and its functional potential. Whereas the latter may vary much with the body (target) site, delivery mode, human target population, and health benefit envisaged microbial assessment of the probiotic product quality is more straightforward. The range of stakeholders that need to be informed on probiotic quality assessments is extremely broad, including academics, food and biotherapeutic industries, healthcare professionals, competent authorities, consumers, and professional press. In view of the rapidly expanding knowledge on this subject, the Belgian Superior Health Council installed Working Group "8651 Probiotics" to review the state of knowledge regarding the methodologies that make it possible to characterize strains and products with purported probiotic activity. This advisory report covers three main steps in the microbial quality assessment process, i.e. (i) correct species identification and strain-specific typing of bacterial and yeast strains used in probiotic applications, (ii) safety assessment of probiotic strains used for human consumption, and (iii) quality of the final probiotic product in terms of its microbial composition, concentration, stability, authenticity, and labeling.

Screening fecal enterococci from Greek healthy infants for susceptibility to antimicrobial agents

Enterococci are among the first lactic acid bacteria to colonize the neonatal gastrointestinal tract, but they are also characterized as significant nosocomial pathogens. The aim of this study was to investigate the incidence of antibiotic resistance in enterococci isolated from neonates' gut microbiota as well as the presence of genetic determinants encoding for certain antibiotic resistance traits. A total of 263 fecal samples derived from 97 infants were collected on day 4, 30, and 90 after delivery. Enterococcus faecalis was the most frequently identified species (54.6%) followed by E. faecium, while E. casseliflavus/E. flavescens and E. gallinarum were also traced. The isolates were examined for their resistance to 12 antibiotics. Rifampicin resistance was the highest observed (53.2%), followed by resistance to tetracycline (42.0%), erythromycin (35.7%), and vancomycin (11.2%). Multiresistant strains were highly prevalent. Only intrinsic vancomycin resistance (vanC1 and vanC2/C3) was traced. The ermB gene was detected in 49 out of 96 erythromycin-resistant isolates, while tet genes were detected in 51 out of 113 tetracycline-resistant strains, with tet(L) being the most frequently observed. In conclusion, antibiotic-resistant enterococci are already established in the fecal microbiota of healthy neonates, from the first days of an infant's life.

The impact of meals on a probiotic during transit through a model of the human upper gastrointestinal tract

Commercial literature on various probiotic products suggests that they can be taken before meals, during meals or after meals or even without meals. This has led to serious confusion for the industry and the consumer. The objective of our study was to examine the impact of the time of administration with respect to mealtime and the impact of the buffering capacity of the food on the survival of probiotic microbes during gastrointestinal transit. We used an in vitro Digestive System (IViDiS) model of the upper gastrointestinal tract to examine the survival of a commercial multi-strain probiotic, ProtecFlor®. This product, in a capsule form, contains four different microbes: two lactobacilli (Lactobacillus helveticus R0052 and Lactobacillus rhamnosus R0011), Bifidobacterium longum R0175 and Saccharomyces cerevisiae boulardii. Enumeration during and after transit of the stomach and duodenal models showed that survival of all the bacteria in the product was best when given with a meal or 30 minutes before a meal (cooked oatmeal with milk). Probiotics given 30 minutes after the meal did not survive in high numbers. Survival in milk with 1% milk fat and oatmeal-milk gruel were significantly better than apple juice or spring water. S. boulardii was not affected by time of meal or the buffering capacity of the meal. The protein content of the meal was probably not as important for the survival of the bacteria as the fat content. We conclude that ideally, non-enteric coated bacterial probiotic products should be taken with or just prior to a meal containing some fats.

Antibiotic resistance in faecal microbiota of Greek healthy infants

Increasing use of antibiotics for the treatment of infectious diseases and also for non-therapeutic reasons (agriculture, animal husbandry and aquaculture) has led to the increasing incidence of antibiotic resistance and the ineffectiveness of antimicrobial treatment. Commensal intestinal bacteria are very often exposed to the selective pressure of antimicrobial agents and may constitute a reservoir of antibiotic resistance determinants that can be transferred to pathogens. The present study aimed to investigate the antibiotic susceptibility profile and the presence of selected resistance genes in cocci isolated from the faecal microbiota of 35 healthy, full-term infants at 4, 30 and 90 days after delivery. A total of 148 gram-positive, catalase-negative cocci were isolated and tested for susceptibility to 12 different antibiotics by disk-diffusion technique. Multiplex PCR analysis was performed for the identification of Enterococcus spp. isolates and the simultaneous detection of vancomycin-resistance genes. PCR-based methodology was used also for identification of tetracycline and erythromycin resistance determinants. Identification results indicated E. faecalis as the predominant species (81 strains), followed by E. faecium, E. casseliflavus/E. flavescens and E. gallinarum. High prevalence of resistance to tetracycline (39.9%), erythromycin (35.1%), vancomycin (19.6%) and to nucleic acid synthesis inhibitors was detected. PCR data revealed 24 out of 52 erythromycin-resistant isolates carrying the ermB gene and 32 out of 59 tetracycline-resistant strains carrying tet genes, with tet(L) determinant being the most frequently detected. Only intrinsic vancomycin resistance (vanC1 and vanC2/C3) was reported among tested isolates. In conclusion, erythromycin and tetracycline acquired resistant traits are widespread among faecal cocci isolates from Greek, healthy infants under no apparent antimicrobial selective pressure.

Enumeration of bifidobacteria using Petrifilm™ AC in pure cultures and in a fermented milk manufactured with a commercial culture of Streptococcus thermophilus

Bifidobacteria are probiotic microorganisms that are widely used in the food industry. With the aim of using of Petrifilm™ Aerobic Count (AC) plates associated with selective culture media, aliquots of sterile skim milk were inoculated separately with four commercial cultures of bifidobacteria. These cultures were plated by both the conventional method and Petrifilm™AC, using the culture media NNLP and ABC. The cultures were incubated under anaerobiosis at 37 °C for 24, 48 and 72 h. No significant differences (p > 0.05) were observed between the obtained counts at 48 and 72 h. Bifidobacteria counts in ABC were usually higher than in NNLP, independent of the plating method. Subsequently, fermented milk was prepared with a Streptococcus thermophilus strain, and aliquots were inoculated with the same bifidobacteria. Then, the fermented milks were submitted to microbiological analysis for bifidobacteria enumeration using the same culture media and methodologies previously described, incubated under anaerobiosis at 37 °C for 48 h. Again, bifidobacteria counts in ABC were higher than in NNLP, with significant differences for some cultures (p < 0.05). The counts obtained by both methodologies presented significant correlations (p < 0.05). The results indicate the viability of Petrifilm™AC as an alternative method for bifidobacteria enumeration when associated to specific culture media, specially the ABC.

Recommendations for the viability assessment of probiotics as concentrated cultures and in food matrices

Due to the fact that probiotic cells need to be alive when they are consumed, culture-based analysis (plate count) is critical in ascertaining the quality (numbers of viable cells) of probiotic products. Since probiotic cells are typically stressed, due to various factors related to their production, processing and formulation, the standard methodology for total plate counts tends to underestimate the cell numbers of these products. Furthermore, products such as microencapsulated cultures require modifications in the release and sampling procedure in order to correctly estimate viable counts. This review examines the enumeration of probiotic bacteria in the following commercial products: powders, microencapsulated cultures, frozen concentrates, capsules, foods and beverages. The parameters which are specifically examined include: sample preparation (rehydration, thawing), dilutions (homogenization, media) and plating (media, incubation) procedures. Recommendations are provided for each of these analytical steps to improve the accuracy of the analysis. Although the recommendations specifically target the analysis of probiotics, many will apply to the analysis of commercial lactic starter cultures used in food fermentations as well.

New detection systems of bacteria using highly selective media designed by SMART: selective medium-design algorithm restricted by two constraints

Culturing is an indispensable technique in microbiological research, and culturing with selective media has played a crucial role in the detection of pathogenic microorganisms and the isolation of commercially useful microorganisms from environmental samples. Although numerous selective media have been developed in empirical studies, unintended microorganisms often grow on such media probably due to the enormous numbers of microorganisms in the environment. Here, we present a novel strategy for designing highly selective media based on two selective agents, a carbon source and antimicrobials. We named our strategy SMART for highly Selective Medium-design Algorithm Restricted by Two constraints. To test whether the SMART method is applicable to a wide range of microorganisms, we developed selective media for Burkholderia glumae, Acidovorax avenae, Pectobacterium carotovorum, Ralstonia solanacearum, and Xanthomonas campestris. The series of media developed by SMART specifically allowed growth of the targeted bacteria. Because these selective media exhibited high specificity for growth of the target bacteria compared to established selective media, we applied three notable detection technologies: paper-based, flow cytometry-based, and color change-based detection systems for target bacteria species. SMART facilitates not only the development of novel techniques for detecting specific bacteria, but also our understanding of the ecology and epidemiology of the targeted bacteria.