106 research outputs found
Probiotic Microorganisms for Shaping the Human Gut Microbiota - Mechanisms and Efficacy into the Future
No full textSummary
The use of bacteria as beneficial biological agents to be used as food ingredients or as active components of food supplements dates back to the early 1900’s.
These bacteria must reach the human gut in a viable form and in numbers sufficiently high to attain a substantial presence amongst the thousands of bacteria inhabiting the gut; they have also to exert some beneficial action.
These beneficial actions have been supported by hundreds of papers, the vast majority of them dealing with subjects in which the ratio among the different bacterial groups of the gut were altered by pathological conditions; the administration of probiotic bacteria are able to restore the function of the gut microbiota.
In healthy people the action of probiotics is possibly related to different mechanisms, linked to strain-specific action of probiotics and relying on the replacement of some autochthonous bacteria with specifically selected probiotic strains
Microbiological and molecular characterization of commercially available probiotics containing Bacillus clausii from India and Pakistan
No full textProbiotics are actively used for treatment of diarrhoea, respiratory infections, and prevention of infectious gastrointestinal diseases. The efficacy of probiotics is due to strain-specific features and the number of viable cells; however, several reports of deviations from the label in the actual content of strains in probiotic products are a matter of concern. Most of the available data on quality focuses on probiotic products containing lactobacilli and/or bifidobacteria, while very few data are available on spore-forming probiotics. The present study evaluates the label claims for spore count and species identification in five commercial probiotic products marketed in India and Pakistan that claim to contain Bacillus clausii: Tufpro, Ecogro, Enterogermina, Entromax, and Ospor. Bacterial enumeration from three batches was done by microbiological plating methods by two independent operators. Species identification was done using PCR amplification and sequence analysis of the 16S rRNA gene, and determination of the total amount of species present in the products was done using PCR-denaturing gradient gel electrophoresis (PCR-DGGE) analysis followed by DNA sequencing of the excised bands. Plate count methods demonstrated poor correlations between quantitative label indications and bacteria recovered from plates for Tufpro, Ecogro, and Ospor. The 16S rRNA analysis performed on bacteria isolated from plate counts showed that only Enterogermina and Ospor contained homogenous B. clausii. PCR-DGGE analysis revealed that only Enterogermina had a homogenous B. clausii population while other products had mixed bacterial populations. In conclusion, the current analysis clearly demonstrates that of the five analysed commercial probiotics, only Enterogermina followed the label claims
Microbiological Cutoff Values: A Critical Issue in Phenotypic Antibiotic Resistance Assessment of Lactobacilli and Bifidobacteria
No full textThe purpose of this study was to assess the antimicrobial resistance profiles of several strains of Lactobacillus and Bifidobacterium spp. of probiotic interest. The International Organization for Standardization method was used to determine the minimal inhibitory concentrations of the antibiotics recommended by the European Food Safety Authority (EFSA). As a result, some of the tested microorganisms showed a visible growth up to the microbiological cutoff values indicated by EFSA guidelines in 2012. We were not able to categorize these strains as susceptible or resistant on the basis of antimicrobial resistance phenotypic testing as EFSA document does not explicitly deal with such a phenotypic condition where strains grow at antibiotic concentrations up to the established cutoff value. Although a few strains have been analyzed for this study, our findings highlight a potential challenge in accurately determining the antibiotic resistance in specific strains relevant for human and animal health
Abundance and Diversity of Hydrogenotrophic Microorganisms in the Infant Gut before the Weaning Period Assessed by Denaturing Gradient Gel Electrophoresis and Quantitative PCR
No full textDelivery mode (natural vs. cesarean) and feeding type (breast vs. formula feeding) are relevant factors for neonatal gut colonization. Biomolecular methods have shown that the ecological structure of infant microbiota is more complex than previously proposed, suggesting a relevant presence of unculturable bacteria. It has also been postulated that among unculturable bacteria, hydrogenotrophic populations might play a key role in infant health. Sulfate-reducing bacteria (SRB), acetogens, and methanogenic archaea use hydrogenotrophic pathways within the human colon. However, to date, few studies have reported detection of hydrogenotrophic microorganisms in newborns, possibly because of limitations on available group-specific, culture-independent quantification procedures. In the present work, we analyzed 16 fecal samples of healthy babies aged 1–6 months by means of quantitative PCR (qPCR) targeting the 16S rRNA or metabolic functional genes and by denaturing gradient gel electrophoresis (DGGE). qPCR data showed quantifiable levels of methanogens, SRB, and acetogens in all samples, indicating that the relative abundances of these microbial groups were not affected by delivery mode (natural vs. caesarian). DGGE revealed a high prevalence of the Blautia genus within the acetogenic bacteria despite strong interindividual variability. Our preliminary results suggest that hydrogenotrophic microorganisms, which have been a neglected group to date, should be included in future ecological and metabolic studies evaluating the infant intestinal microbiota
QUALITATIVE AND QUANTITATIVE EVALUATION OF GUT MICROBIAL POPULATIONS IN SEVERELY OBESE PATIENTS FOLLOWING BILIO-INTESTINAL BYPASS
No full textBackground and aim: Several recent studies showed that the altered gastrointestinal
microbiota linked to obesity changes after gastric bypass in humans
and rats, and it has been suggested that these changes may underlie some of
the beneficial effects of bariatric surgery.
Material and methods: To deeply characterize the impact of weight-loss
surgery on gut microbial ecology, we collected fecal samples from severely
obese patients (n=11) before and six months after bilio-intestinal bypass.
Gut microbial populations were qualitatively and quantitatively evaluated by
Denaturing Gel Gradient Electrophoresis (DGGE), 16S ribosomal RNA gene
sequencing and real-time PCR.
Results: Obese individuals were found to harbor a distinctive community
dominated at the genus/species level by members of the clostridial clusters IV
and XIVa, specifically Roseburia/E. rectale spp, Blautia spp, Ruminococcus
spp, Dorealongicatena. Compared to pre-operative levels, the fecal microbial
profiles of patients revealed a significant increase in the proportion of Lactobacillus
crispatus, a major lactate producer, and in the population related to
Megasphaer aelsdenii, which is known to be an efficient lactate-utilizer. At
high taxonomic level, the BIBP individuals exhibited reduced Bacteroides-
Prevotella, major genera of the Bacteroidetes phylum, but no significant
differences in the relative abundance of Firmicutes in comparison with obese
patients prior to surgery.
Conclusions: The compositional shifts of the fecal microbial community
observed in this study suggest a reprogramming of the bacterial fermentation
routes in the gut following bilio-intestinal bypass. Further research is therefore
called for to understand the implications on host energy homeostasis and
support a possible contribution of gut bacteria in substantial weight loss and
metabolic improvement after bariatric surgery
Adhesion of ectomycorrhizal bacteria to plant cells: an in vitro evidence.
No full textIn this study we have investigated, by combining microbial and microscopical techniques, the adhesion ability of bacteria present in Tuber borchii ectomycorrhizosphere. Our data demonstrate that a common pool of bacteria - Pseudomonas, Bacillus, Micrococcus and Moraxella - occurs in all ectomycorrhizal homogenates and that most of these bacteria are able to attach in vitro to plant cells
Detailed analyses of the bacterial populations in processed cocoa beans of different geographic origin, subject to varied fermentation conditions
No full textThe quality of chocolate is influenced by several parameters, one of which is bacterial diversity during fermentation and drying; a crucial factor for the generation of the optimal cocoa flavor precursors. Our understanding of the bacterial populations involved in chocolate fermentation can be improved by the use of high-throughput sequencing technologies (HTS), combined with PCR amplification of the 16S rRNA subunit. Here, we have conducted a high-throughput assessment of bacterial diversity in four processed samples of cocoa beans from different geographic origins. As part of this study, we also assessed whether different DNA extraction methods could affect the quality of our data. The dynamics of microbial populations were analyzed postharvest (fermentation and sun drying) and shipment, before entry to the industrial process. A total of 691,867 high quality sequences were obtained by Illumina MiSeq sequencing of the two bacterial 16S rRNA hypervariable regions, V3 and V4, following paired-read assembly of the raw reads. Manual curation of the 16S database allowed us to assign the correct taxonomic classifications, at species level, for 83.8% of those reads. This approach revealed a limited biodiversity and population dynamics for both the lactic acid bacteria (LAB) and acetic acid bacteria (AAB), both of which are key players during the acetification and lactic acid fermentation phases. Among the LAB, the most abundant species were Lactobacillus fermentum, Enterococcus casseliflavus, Weissella paramesenteroides, and Lactobacillus plantarum/paraplantarum. Among the AAB, Acetobacter syzygii, was most abundant, then Acetobacter senegalensis and Acetobacter pasteriuanus. Our results indicate that HTS approach has the ability to provide a comprehensive view of the cocoa bean microbiota at the species level
Effects of two different high-fat diets on the gut microbiota of adult mice
No full textRecently, we reported the short-term changes in the intestinal bacterial community of weaning mice induced by a diet high in unsaturated fat (1). Here, we investigate the effects of both saturated and unsaturated fat diets on caecal microbiota and physiological features of adult mice over a prolonged period of time. C57BL/6 mice were fed either a low-fat diet (LFD); a high-fat, soy oil-based diet (HFSD); or a high-fat, coconut oil-based diet (HFCD). Six mice from each group were killed after 2 (W2) and 8 weeks (W8) of dietary exposure. Daily weight gain and abdominal fat were determined. Samples of blood for metabolic status assessment, caecum tissue for histological evaluation and caecum content for microbiology analysis by DGGE (2) were collected. HFSD and HFCD mice showed a higher daily weight gain both at W2 and W8, and an increased abdominal fat as compared to LFD mice (P<0.05). Blood cholesterol was higher in HFSD (W2) and HFCD (W2 and W8) than in LFD mice (P<0.05). At W8 the histological analysis of the caecum evidenced that HFSD mice showed an increment of lesions of the mucosa (P≤0.01) and inflammatory cell infiltration (P≤0.05) compared to LFD. Visual inspection of the DGGE gel showed diet-dependent differences in band intensities: a band of reduced intensity in both HFSD and HFCD mice at W2 and W8 was identified as Lactobacillus gasseri, whereas two bands of increased intensity as compared to LFD mice were related to Clostridium populeti and Gordonibacter pamelaeae upon sequencing. DGGE data were confirmed by real-time PCR data. Cluster analysis of DGGE fingerprints revealed that HFSD and HFCD mice samples were distinctly grouped from the LFD control mice both at W2 and W8. These results corroborate previous findings on the impact of dietary fat on the gut microbial ecosystem and the physiology of the host.
1. Patrone, V., et al. (2012) Short-term modifications in the distal gut microbiota of weaning mice induced by a high-fat diet. Microbiology 158, 983-992
2. Walter, J., et al. (2000) Detection and identification of gastrointestinal Lactobacillus species by using denaturing gradient gel electrophoresis and species-specific PCR primers. Appl. Environ. Microbiol. 66, 297–30
Assessment of antibiotic resistance in staphylococci involved in fermented meat product processing
No full textThe production chain of fermented sausages can be considered a major source of the dissemination of antibiotic resistance (AR), spreading from farm to the final product. The natural microbiota involved in the complete process may carry AR genes which can be potentially transferred to pathogens or opportunistic bacteria thus representing a risk to human and animal health. Coagulase-negative staphylococci are a dominant microbial group in fermented sausages and often used as starter cultures. Few studies are available on their potential for AR gene transference. This mini-review focuses on the assessment of AR in staphylococci associated with sausage production chain combining traditional analyses with a metagenomic approach, in order to draw some guidelines to prevent AR spread
Exploring the bioaccessibility of polyphenols and glucosinolates from Brassicaceae microgreens by combining metabolomics profiling and computational chemometrics
No full textMicrogreens constitute natural -based foods with health -promoting properties mediated by the accumulation of glucosinolates (GLs) and phenolic compounds (PCs), although their bioaccessibility may limit their nutritional potential. This work subjected eight Brassicaceae microgreens to in vitro gastrointestinal digestion and large intestine fermentation before the metabolomics profiling of PCs and GLs. The application of multivariate statistics effectively discriminated among species and their interaction with in vitro digestion phases. The flavonoids associated with arugula and the aliphatic GLs related to red cabbage and cauliflower were identified as discriminant markers among microgreen species. The multi-omics integration along in vitro digestion and fermentation predicted bioaccessible markers, featuring potential candidates that may eventually be responsible for these functional foods' nutritional properties. This combined analytical and computational framework provided a promising platform to predict the nutritional metabolome-wide outcome of functional food consumption, as in the case of microgreens
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