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At the beginning of the twenty-first century, microbiological studies on human milk started to describe the existence of its own microbiota. Hygienically collected milk samples from healthy women contain a relatively low bacterial load consisting mostly of Staphylococcus, Streptococcus, and other Gram-positive bacteria (Corynebacterium, Propionibacterium, Lactobacillus and Bifidobacterium). DNA from strict anaerobic bacteria is also detected in human milk samples. Colostrum and milk bacteria may play a key role in driving the development of the infant gut microbiota, the correct maturation of the infant immune system and the improvement of tolerance mechanisms. A well-balanced human milk microbiota is also relevant for maternal breast health. The origin of human milk bacteria still remains largely unknown. Infant’s oral cavity and maternal skin may contaminate milk. Additionally, selected bacteria of the maternal digestive microbiota may access the mammary glands through oral- and entero-mammary pathways by involving mononuclear cells for their transport. These pathways would provide new opportunities for manipulating maternal-fetal microbiota, reducing the risk of preterm birth or infant diseases.

Trabajo presentado en el 6th International Conference on Food Digestion, celebrado en Granada (España), del 2 al 4 de abril de 2019, [Introduction] Milk is a complex food with 3.3% protein content and is fundamental in the diet throughout the all life and especially during childhood. However, cow`s milk protein allergy (CMPA) is very common in infancy and the only therapeutic option is a dairy elimination diet. The impact of the absence of milk proteins and dairy products in the gut ecosystem development of the infant has rarely been assessed. [Objective] To evaluate the intestinal changes in infants with non-IgE mediated CMPA after successful standardized oral challenges (SOCs) and introduction of milk in their diet. [Methodology] Twelve allergic children (between 1 and 2 years old) that were initially on a milk restriction diet provided stool samples before SOCs, and a week and a month after introduction of milk. Changes in the intestinal microbiota populations were determined by high-throughput sequencing of the 16S rRNA gene, meanwhile diverse microbial metabolites (short chain fatty acids and indoles) were quantified by chromatographic methods. [Main findings] The introduction of milk in infants that developed tolerance acquisition increased significantly the levels of fecal lactic acid bacteria. Microbial metabolites derived from the fermentation of proteins, such as branched chain fatty acids and p-cresol diminished. Statistical differences were observed between infants that were consuming probiotics (Lactobacillus rhamnosus GG) during the restriction diet period and those that were not. [Conclusion] The introduction of dairy products in the diet is accompanied by modifications in the infant gut environment through changes in the microbiota and protein metabolic end-products. Consumption of probiotics may affect the response to SOC with milk.

Bifidobacteria are among the predominant microorganisms during infancy, being a dominant microbial group in the healthy breastfed infant and playing a crucial role in newborns and infant development. Not only the levels of the Bifidobacterium genus but also the profile and quantity of the different bifidobacterial species have been demonstrated to be of relevance to infant health. Although no definitive proof is available on the causal association, reduced levels of bifidobacteria are perhaps the most frequently observed alteration of the intestinal microbiota in infant diseases. Moreover, Bifidobacterium strains have been extensively studied by their probiotic attributes. This review compiles the available information about bifidobacterial composition and function since the beginning of life, describing different perinatal factors affecting them, and their implications on different health alterations in infancy. In addition, this review gathers exhaustive information about pre‐clinical and clinical studies with Bifidobacterium strains as probiotics in neonates. This review has received funding from the Project AGL2017-83653R funded by the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU)/Agencia Estatal de Investigación (AEI/10.13039/501100011033/) and FEDER “Una manera de hacer Europa”. S.A. was the recipient of a postdoctoral Juan de la Cierva-Incorporación Contract (Ref. IJCI-2017-32156) funded by MCIU/AEI/10.13039/501100011033.

Bacteroides is among the most abundant microorganism inhabiting the human intestine. They are saccharolytic bacteria able to use dietary or host-derived glycans as energy sources. Some Bacteroides fragilis strains contribute to the maturation of the immune system but it is also an opportunistic pathogen. The intestine is the habitat of most Bifidobacterium species, some of whose strains are considered probiotics. Bifidobacteria can synthesize exopolysaccharides (EPS), which are complex carbohydrates that may be available in the intestinal environment. We studied the metabolism of B. fragilis when an EPS preparation from bifidobacteria was added to the growth medium compared to its behavior with added glucose. 2D-DIGE coupled with the identification by MALDI-TOF/TOF evidenced proteins that were differentially produced when EPS was added. The results were supported by RT qPCR gene expression analysis. The intracellular and extracellular pattern of certain amino acids, the redox balance and the a-glucosidase activity were differently affected in EPS with respect to glucose. These results allowed us to hypothesize that three general main events, namely the activation of amino acids catabolism, enhancement of the transketolase reaction from the pentose-phosphate cycle, and activation of the succinate-propionate pathway, promote a shift of bacterial metabolism rendering more reducing power and optimizing the energetic yield in the form of ATP when Bacteroides grow with added EPS. Our results expand the knowledge about the capacity of B. fragilis for adapting to complex carbohydrates and amino acids present in the intestinal environment. © 2015 Rios-covian, Sanchez, Salazar, Martinez, Redruello, Gueimonde and De los Reyes-Gavilan., This work was financed by projects AGL2010-16525 and AGL2013-43770-R from Plan Nacional/Plan Estatal de I+D+I (Spanish Ministry of Economy and Competitiveness, MINECO). The activity of Probiotics and Prebiotics Group is being partly supported through the Grant GRUPIN14-043 from Plan Regional de Investigación del Principado de Asturias. Both, national and regional grants received cofounding from European Union FEDER funds. DR-C was the recipient of predoctoral FPI fellowship whereas BS enjoys a Ramon and Cajal contract from MINECO. NS benefits from a Clarin post-doctoral contract (Marie Curie European CoFund Program) cofinanced by Plan Regional de Investigación del Principado de Asturias, Spain. We acknowledge the excellent technical assistance of Lidia Alaez, whose technician contract was partially supported by the project AGL2010-16525 and by Plan Regional de Investigación del Principado de Asturias, through the grant COF 13-020.

Cow's milk protein allergy (CMPA) is the most common allergy in the first year of life. Non-IgE mediated CMPA is characterized by digestive symptoms and tolerance development before the age of three. Gut microbiota composition in early life has been associated with food allergy. The ingestion of different foods/nutrients may mark different shifts in the microbial colonization of the infant intestine as well as the consumption of probiotics. Aim: To analyze changes in microbiota composition and metabolic and cytokine profiles in fecal samples from infants with non-IgE mediated CMPA after successful milk challenges, tolerance acquisition, and increasing dairy introduction in their diet. Methods: Twelve children with CMPA, aged between 1 and 2 years old, were recruited for the study. Participants were initially consuming hypoallergenic hydrolyzed formulas (four of them supplemented with the probiotic Lactobacillus rhamnosus GG), before being exposed to a standardized oral challenge (SOC) with cow's milk. Fecal samples were collected before, 1 week, and 1 month after performing the SOC. Changes in gut microbiota were determined by high-throughput amplicon sequencing of the 16S rRNA gene. Levels of lactobacilli were also determined by quantitative PCR (qPCR). Microbial metabolites were analyzed by chromatographic methods and fecal cytokines related to the Th1/Th2 balance were determined by immunoassay. Results: Lactic acid bacteria significantly increased in infants who outgrew non-IgE CMPA, after the introduction of milk. Microbial metabolites derived from the fermentation of proteins, such as branched chain fatty acids, and p-cresol, diminished. After the SOC, some cytokines related to inflammation (TNF-α, IFN-γ) increased. Accompanying the introduction of an unrestricted diet, we found significant differences in fecal microbial composition, metabolites, and cytokines between infants who did not consume the probiotic L. rhamnosus GG and those that did. Conclusions: These findings indicate that the introduction of intact milk proteins is followed by modifications in the infant gut environment through changes in immune mediators, microbiota, and its metabolic end-products. Consumption of probiotics during CMPA may contribute to gut homeostasis by fine-tuning these profiles., This research was funded by 2ª Convocatoria de Ayudas a Proyectos de Investigación Científica del Instituto Danone and grant IDI/2018/000236 from the Plan for Research, Development and Innovation of the Principado de Asturias 2018–2020 co-financed by the European Regional Development Funds (FEDER).

Bifidobacterium animalis subsp. lactis IPLA 20020 and Lactobacillus gasseri IPLA 20212, two strains isolated from human samples, were evaluated for safety and influence over the intestinal microbiota and cytokine production by the intestinal tissue of adult BALB/c mice. Mice were divided into four groups receiving during 8 days PBS or a suspension of each strain, prepared fresh or lyophilized (bifidobacteria), at an amount of 4x108 viable cells/day. This dose could be comparable to the probiotic intake of a human adult who consumed about 100-200 mL of functional fermented milk per day, considering the usual level of probiotics in commercial products. No microbial translocation to liver or alterations in food intake, weight, and behavior were observed in treated mice. Intestinal content of secretory immunoglobulin A (s-IgA) was not affected, discarding any adverse effect on the mucosa-associated immunity. The profile of intestinal proinflammatory/regulatory cytokines after intervention evidenced that the microbial strain administered and its cellular state (fresh or lyophilized) as well as the host tissue analyzed (small or large intestine) influenced the immune response and suggests a moderate shift towards a T helper 1 profile (Th1) in the large intestine after the administration of both strains. Changes on relative levels of some intestinal microbial groups were evidenced after intervention. It is noteworthy that butyrate was positively associated with a balanced pro-Th1 immune response. Therefore, B. animalis subsp. lactis IPLA20020 and L. gasseri IPLA 20212 could be considered potential probiotic candidates to be included in functional foods for balancing the intestinal immune response., The present work was financed by the following projects: AGL2013-43770-R and PCIN-2015-233 (Project EarlyMicroHealth from the EU Joint Program Initiative HDHL), funded by the Spanish Plan Estatal de I+D+I (Ministry of Economy and Competitiveness; MINECO), Project PICT-2016-0256 supported by the Argentinian Scientific and Technological Research Funds (FonCyT), and grant GRUPIN14-043 funded by Plan Regional de Investigación del Principado de Asturias, Spain. Alicja M. Nogacka benefits from a predoctoral contract granted by MINECO. Nuria Salazar was the recipient of a Juan de la Cierva postdoctoral contract granted by MINECO and she is currently the recipient of a postdoctoral contract awarded by the Fundación para la Investigación Biosanitaria de Asturias (FINBA). The critical reading of the manuscript and useful comments of Dr. Sonia González (Department of Functional Biology, University of Oviedo, Spain) are acknowledged.

In the modern food technology era, one of the aims of food safety and quality is to eliminate or reduce the number of microorganisms in food. This may now be changing. In particular, the importance of live microorganisms as beneficial food constituents is now being recognized. Microorganisms present in food that contribute to the human diet include not only viable bacteria but also metabolites and bioactive components. Yogurt is one of the most biologically active foods consumed by humans. It is an excellent source of proteins, vitamins, and minerals. Additionally, the nutritional value is especially high relative to cost. Potential nutritional benefits are also associated with the ingestion of the bacteria that are ordinarily present at the time of consumption. Thus, yogurt serves as a major source of live bacteria in the human diet, as well as a delivery vehicle for added probiotic bacteria. Yogurt may provide a simple and affordable solution for enhancing the nutritional value of the diet, including the intake of live bacteria and their metabolites. A further benefit may be obtained when yogurt is used as a carrier for specific probiotic bacteria and/or prebiotic compounds. These factors suggest that yogurt could have a more visible role in food-based dietary guidelines.

Several in vitro screening tests have been used for selecting probiotic strains; however they often show low predictive value and only a limited number of strains have demonstrated functionality in vivo. The most used in vitro tests represent a very simplified version of the gut environment, especially since they do not consider the accompanying microbiota. Therefore, there is a need to develop sensitive and discriminating in vitro models including the microbiota. Here we developed an in vitro model to discriminate among microbiotas/fecal waters from different population groups. To this end samples were obtained from seven healthy adults, five IBD-patients, ten full-term and ten preterm newborns. Fecal microbiotas were purified and their impact, as well as that of the fecal waters, on HT29 cells was continuously monitored for 22 h using a real-time cell analyzer (RTCA). The composition of the purified microbiotas was assessed by 16S rRNA gene profiling and qPCR and the levels of short chain fatty acids (SCFA) determined by gas chromatography. The microbiota fractions and SCFA concentrations obtained from IBD-patients, full-term and preterm babies, showed clear differences with regard to those of the control group (healthy adults). Moreover, the purified intestinal microbiotas and fecal waters also differed from the control group in the response induced on the HT29 cells assay developed. In short, we have developed a real-time, impedance-based in vitro model for assessing the functional response induced by purified microbiotas and fecal waters upon intestinal epithelial cells. The capability of the assay for discriminating the functional responses induced, by microbiotas or fecal waters from different human groups, promises to be of help on the search for compounds/strains to restore the functionality of the microbiota-host's interaction., This work was financed by projects AGL2013-43770-R and AGL2015-64901-R from Plan Estatal de I + D + I (Spanish Ministry of Economy and Competitiveness, MINECO) and by Grant GRUPIN14-043 from Plan Regional de Investigación del Principado de Asturias, Spain. Both national and regional grants received cofounding from the European Union FEDER funds. AMN is the recipient of a predoctoral contract and NS benefits from a Juan de la Cierva postdoctoral contract, both granted by MINECO

The functional food market, including products formulated to maintain a “healthy” gut microbiota, i.e. probiotics and prebiotics, has increased enormously since the end of the last century. In order to favor the competitiveness of this sector, as well as to increase our knowledge of the mechanisms of action upon human health, new probiotic strains and prebiotic substrates are being studied. This review discusses the use of exopolysaccharides (EPS), both homopolysaccharides (HoPS) and heteropolysaccharides (HePS), synthesized by lactic acid bacteria and bifidobacteria as potential prebiotics. These extracellular carbohydrate polymers synthesized by some gut inhabitants seem to be resistant to gastrointestinal digestion; these are susceptible as well to biodegradability by the intestinal microbiota depending on both the physicochemical characteristics of EPS and the pool of glycolytic enzymes harbored by microbiota. Therefore, although the chemical composition of these HoPS and HePS is different, both can be fermentable substrates by intestinal inhabitants and good candidates as prebiotic substrates. However, there are limitations for their use as additives in the food industry due to, on the one hand, their low production yield and, on the other hand, a lack of clinical studies demonstrating the functionality of these biopolymers., The authors are grateful to the financial support given to this research topic by the (currently) Ministry of Economy and Competiveness (MINECO) throughout European Union FEDER funds. The acknowledged ongoing projects of the group are AGL2009-09445 and AGL2010-16525.

In vitro models are frequently used in probiotic research. However, such models often fail to predict in vivo functionality and efficacy. This fact complicates the screening process for selecting the most suitable strains, prior to accomplish expensive animal studies and clinical intervention trials. Therefore, additional sensitive, discriminating and cost-effective models are needed to conduct preliminary assays before undertaking human intervention studies definitely proving efficacy. With this purpose in mind, we explored the potential of axenic Drosophila melanogaster populations as well as of these axenic flies treated with probiotic microbial strains as a model to test the effects of probiotics on a subset of developmental and behavioural traits. An axenic D. melanogaster progeny from the wild-type Canton S strain was obtained and its eggs were further developed until pupae eclosion occurred in growth medium containing either of two probiotic strains: Bifidobacterium animalis subsp. lactis Bb12 or Lactobacillus rhamnosus GG. Whereas B. animalis Bb12 colonised the flies, the capacity of L. rhamnosus LGG to colonise was considerably lower in our experimental conditions. Regarding the influence of microbial load on the flies’ development, the axenic condition caused a decrease in egg survival, and lowered adults’ average weight with respect to wild-type flies. Both probiotics were able to counteract these effects. An earlier emergence of adults was observed from eggs treated with L. rhamnosus GG in comparison to the other fly populations. The axenic condition did not influence negative geotaxis behaviour in Drosophila; however, flies mono-associated with B. animalis Bb12 moved faster than wild-type. Our results suggest that the use of axenic/probiotic-treated D. melanogaster populations may be an affordable model for preliminary testing of the effects of probiotics on developmental or behavioural aspects.

The human gut microbiota is engaged in multiple interactions affecting host health during the host's entire life span. Microbes colonize the neonatal gut immediately following birth. The establishment and interactive development of this early gut microbiota are believed to be (at least partially) driven and modulated by specific compounds present in human milk. It has been shown that certain genomes of infant gut commensals, in particular those of bifidobacterial species, are genetically adapted to utilize specific glycans of this human secretory fluid, thus representing a very intriguing example of host-microbe coevolution, where both partners are believed to benefit. In recent years, various metagenomic studies have tried to dissect the composition and functionality of the infant gut microbiome and to explore the distribution across the different ecological niches of the infant gut biogeography of the corresponding microbial consortia, including those corresponding to bacteria and viruses, in healthy and ill subjects. Such analyses have linked certain features of the microbiota/microbiome, such as reduced diversity or aberrant composition, to intestinal illnesses in infants or disease states that are manifested at later stages of life, including asthma, inflammatory bowel disease, and metabolic disorders. Thus, a growing number of studies have reported on how the early human gut microbiota composition/development may affect risk factors related to adult health conditions. This concept has fueled the development of strategies to shape the infant microbiota composition based on various functional food products. In this review, we describe the infant microbiota, the mechanisms that drive its establishment and composition, and how microbial consortia may be molded by natural or artificial interventions. Finally, we discuss the relevance of key microbial players of the infant gut microbiota, in particular bifidobacteria, with respect to their role in health and disease., This work was funded by the EU Joint Programming Initiative “A Healthy Diet for a Healthy Life” (JPI HDHL, http://www.healthydietforhealthylife.eu/) and MIUR to M.V. and by the Spanish MINECO to M.G. (project PCIN-2015-233). A.M. and S.D.P. are partially funded by grants from the Instituto Danone and by the Spanish Plan Estatal de I+D+I (reference AGL2016-78311-R). D.V.S. is a member of the APC Microbiome Institute funded by Science Foundation Ireland (SFI) through the Irish Government's National Development Plan (grant number SFI/12/RC/2273). J.M.R. is in receipt of AGL2016-75476-R (Ministerio de Economía y Competitividad (Spain). J.M. is in receipt of a Starting Investigator Research Grant (SIRG) (no. 15/SIRG/3430) funded by Science Foundation Ireland (SFI).

[Background] In vitro selection tests such as exposure to low pH and bile salts, competitive exclusion of pathogens, adherence to cell lines and prokaryotic-eukaryotic co-cultures have been commonly used to predict the functional properties of lactobacilli and bifidobacteria for their use as probiotics. However, the correlation of in vitro results with in vivo performance remains obscure. [Scope and approach] To review the current state of evidence linking in vitro predictions to in vivo outcomes in selecting probiotic candidates and to discuss the advantages and limitations of the various assays presently available. [Key findings and conclusions] The successful use of lactobacilli and bifidobacteria as traditional probiotics is based on their occurrence in human milk, naturally fermented foods, in the gastrointestinal tract and feces of infants and adults as well as on their culturability, technological robustness and long history of safe use. The lack of standardized protocols for in vitro and in vivo studies hampers comparison of the potential of new species and strains. There is thus a need to conduct selection of potential probiotics in a more robust manner and to focus well-defined in vitro and in vivo studies to document health benefits.

The involvement of the gut microbiota on weight-gain and its relationship with childhood undernutrition and growth has been reported. Thus, the gut microbiota constitutes a potential therapeutic target for preventing growth impairment. However, our knowledge in this area is limited. In this study we aimed at evaluating the relationship among early microbiota, growth, and development in preterm infants. To this end we assessed the levels of specific microorganisms by qPCR, and those of short chain fatty acids by mean of gas-chromatography, in feces from 63 preterm newborns and determined their weight-gain during the first months. The statistical analyses performed indicate an influence of the intestinal microbiota in weight-gain, with the levels of some microorganisms showing a significant association with the weight-gain of the infant. The levels of specific microbial groups during the first days of life were found to affect weight gain by the age of 1 month. Moreover, clustering of the infants on the basis of the microbiota composition at 1 month of age rendered groups which showed differences in weight z-scores. Our results suggest an association between the gut microbiota composition and weight-gain in preterm infants at early life and point out potential microbial targets for favoring growth and maturation in these infants., This work was founded by the EU Joint Programming Initiative–A Healthy Diet for a Healthy Life (JPI HDHL, http://www.healthydietforhealthylife.eu/) and the Spanish Ministry of Economy and Competitiveness (MINECO) (Project EarlyMicroHealth). The Grant GRUPIN14-043 from “Plan Regional de Investigación del Principado de Asturias” is also acknowledged.

The gut microbiota plays an important role in host health. The ageing process affects this microbial community, and therefore, the use of functional foods to restore the microbiota of elderly constitutes an interesting strategy. To this end, probiotics and prebiotics targeted at correcting the specific microbiota alterations occurring during senescence are needed. We performed an in vitro selection of bifidobacterial strains and prebiotic substrates on the basis of their ability to counterbalance the specific microbiota aberrancies previously identified in the elderly population. Batch cultures of faeces from elderly were carried out adding different strains of Bifidobacterium or prebiotics. The effects of these strains/prebiotics upon gut microbiota were assessed by quantitative PCR and the concentrations of short chain fatty acids determined by gas chromatography-FID/MS. The target-specific selection process applied in this study allowed the preliminary selection of two Bifidobacterium strains and a prebiotic fructooligosaccharide on the basis of their specific properties for the modulation of the microbiota of elders. Overall, this study identifies potentially probiotic strains and prebiotic substrates for the development of functional foods specifically targeted to the senior population., The partial funding through the projects AGL2010-16525 and AGL2013-43770R from Plan Nacional de I+D and Project GRUPIN14-043 from Plan de Ciencia, Tecnología e Innovación 2013–2017 (European Union Feder Funds and Principado de Asturias) is also acknowledged. L. Valdés was the recipient of a JAE-Pre fellowship granted by CSIC.

The gut microbiota is the assembly of microorganisms living in our intestine and their genomes are known as the microbiome. The correct composition and functionality of this microbiome is essential for maintaining a “healthy status.” Aging is related to changes in the gut microbiota which are frequently associated with physiological modifications of the gastrointestinal tract, as well as, to changes in dietary patterns, together with a concomitant decline in cognitive and immune function, all together contributing to frailty. Therefore, nutritional strategies directed at restoring the microbiota in the elderly have to be addressed from a global perspective, considering not only the microbiota but also other extra-intestinal targets of action. The present review aims at summarizing the current knowledge on intestinal microbiota alterations and other functions impaired in the elderly and to analyze tools for implementing nutritional strategies, through the use of probiotics, prebiotics or specific nutrients in order to counterbalance such alterations., Authors receive financial support from Plan Estatal de I+D (Spanish Ministry of Economy and Competitiveness) through the project AGL2013-43770-R, and from “Plan Regional de Investigación” of Principado de Asturias through the Grant GRUPIN14-043. Both projects receive cofounding from European Union FEDER funds. N. Salazar benefits from a post-doctoral “Clarín” contract (Marie Curie European Co-Fund Program) linked to the grant ACB14-08 co-funded by the Marie Curie European CoFund Program.

The gastrointestinal tract of mammals hosts a high and diverse number of different microorganisms, known as intestinal microbiota. Many probiotics were originally isolated from the gastrointestinal tract, and they were defined by the Food and Agriculture Organization of the United Nations (FAO)/WHO as “live microorganisms which when administered in adequate amounts confer a health benefit on the host.” Probiotics exert their beneficial effects on the host through four main mechanisms: interference with potential pathogens, improvement of barrier function, immunomodulation and production of neurotransmitters, and their host targets vary from the resident microbiota to cellular components of the gut–brain axis. However, in spite of the wide array of beneficial mechanisms deployed by probiotic bacteria, relatively few effects have been supported by clinical data. In this regard, different probiotic strains have been effective in antibiotic‐associated diarrhea or inflammatory bowel disease for instance. The aim of this review was to compile the molecular mechanisms underlying the beneficial effects of probiotics, mainly through their interaction with the intestinal microbiota and with the intestinal mucosa. The specific benefits discussed in this paper include among others those elicited directly through dietary modulation of the human gut microbiota., Research in our lab is funded by Grants AGL2013‐44039‐R and AGL2013‐44761‐P from the Spanish “Plan Estatal de I+D+I.” Part of the authors is also partially funded by the [15VI013] Contract‐Programme from the University of Vigo and the Agrupamento INBIOMED from DXPCTSUG‐FEDER unha maneira de facer Europa (2012/273). B. S. was recipient of a Ramón y Cajal postdoctoral contract from the Spanish Ministry of Economy and Competitiveness.

The use of selected probiotics, prebiotics and/or synbiotics, constitute an interesting dietary strategy for intestinal microbiota modulation in case of dysbiosis. Species of the genus Bifidobacterium are among the most currently used probiotics for human consumption since they have shown beneficial effects in the prevention and treatment of some disorders. Bifidobacteria are saccharolytic microorganisms, but their ability to use different carbohydrates varies among strains. In this study, we investigate the utilization of three prebiotic substrates (two different short-chain fructo-oligosaccharides [scFOS] and inulin) by strains of Bifidobacterium, in order to determine the synbiotic potential of the different probiotic/prebiotic combinations. Batch culture fermentations from six Bifidobacterium strains (Bifidobacterium longum IPLA20021, B. longum IPLA20022, Bifidobacterium animalis IPLA20031, B. animalis IPLA20032, B. animalis IPLA20020 and B. animalis Bb12) were carried out in the presence of inulin or scFOS (Synergy or Actilight), or glucose, as carbon source. Bifidobacteria levels were quantified by plate counting. The pH and production of organic acids in the different batch-culture fermentations were also determined. Our results showed that all the studied strains of B. animalis and B. longum were able to utilize scFOS but not inulin. The use of scFOS as carbon source affected the pattern of metabolite's production, when compared with cultures carried out in glucose, particularly in the case of B. longum. The results indicated that the scFOS are well suited to be used in combination with B. animalis or B. longum strains for the development of synbiotic foods or food supplements., The partial funding through the project AGL2013-43770R from Plan Nacional de I + D (Ministry of Science and Innovation) and Project GRUPIN14-043 from Plan de Ciencia, Tecnología e Innovación 2013–2017 (Feder Funds and Principado de Asturias) are also acknowledged. L. Valdés was the recipient of a JAE-Pre fellowship granted by CSIC.

Microbial communities inhabiting the human host play important roles in maintaining health status, including reproduction and early life programming, which is particularly important in the context of preterm neonates’ health. Preterm birth (PTB) is often the result of a microbial dysbiosis or infection. In addition, preterm neonates experience different levels of organ immaturity and an abnormal gut microbiota establishment, as compared to full-term neonates. This exacerbates their developmental problems and can have negative consequences at systemic level. In addition, preterm babies are commonly exposed to delayed enteral feeding and hospital environments, which increases the risk of short- and long-term health problems. Some of these clinical conditions, such as necrotizing enterocolitis or sepsis, may be life threatening, whereas others may translate into life-long conditions, including cognitive problems. Increasing scientific interest has focused on understanding developmental problems in preterm neonates related to abnormalities in the settlement of their microbial communities, with the final goal of selecting appropriate microbiome-targeted strategies (eg, probiotics), to reduce preterm health risks and improve overall quality of life. This review aims to summarize current knowledge on microbiological factors influencing PTB initiation and gastrointestinal development, and on the health consequences to the preterm neonate. Scientific evidences on dietary strategies reducing PTB incidence and minimizing sequelae in this particularly sensitive human group subpopulation are also discussed.