Gut-gonad crosstalk in mice exposed to a "chemical cocktail" combining metabolomics and microbial profile by amplicon sequencing

Testes are very prone to be damaged by environmental pollutants, but there is a lack of information about the impact of "chemical cocktails" (CC) on the testicular metabolome and the possible influence in the gut-gonad crosstalk. For this, BALB/c mice were given flumequine and diclofenac orally in food and potentially toxic trace elements (Cd, Hg, As) in drinking water. A mice group was supplemented with selenium, a well-known antagonist against many pollutants. Our results revealed that the steroid 5-alpha-androstan-17-beta-ol propionate, suggested as a parameter of androgenicity independent of testosterone levels, proline that improves reproductive indicators in male rabbits affected by environmental stress) among others metabolites are only present after CC exposure with rodent and selenium supplemented diet. Selenium also antagonized the up-or down-regulation of anandamide (20:l, n-9) (p < 0.001 and FC 0.54 of CC vs C but p > 0,05 and FC 0.74 of CC-Se vs C), that regulates gonadotropin-releasing hormones in mammals, 2,3-dinor-11b-PGF2a (p < 0.001 and FC 0.12 of CC vs C but p > 0,05 and FC 0.34 of CC-Se vs C), which has been related with reproductive hormones, besides others testicular metabolites altered by the exposure to the CC and reversed the levels to control. Moreover, numerous significant associations between gut microbes and testicular metabolites indicated a possible impact of pollutants in the testes mediated by gut microbiota due to a gut-gonad crosstalk.

Impact of "chemical cocktails" exposure in shaping mice gut microbiota and the role of selenium supplementation combining metallomics, metabolomics, and metataxonomics

Biological systems are exposed to a complex environment in which pollutants can interact through synergistic or antagonistic mechanisms, but limited information is available on the combined effects. To this end, conventional and antibiotic-treated (Abx) mice models were fed regular rodent or selenium (Se) supplemented diets and exposed to a "chemical cocktail" (CC) including metals and pharmaceuticals. Metallomics, metabolomics, and metataxomics were combined to delve into the impact on gut microbiota, plasma selenoproteome, metabolome, and arsenic metabolization. At the molecular level, Se decreased the concentration of the antioxidant glutathione peroxidase in plasma and increased the arsenic methylation rate, possibly favoring its excretion, but not in the Abx and also plasma metabolomes of Abx, and Abx-Se were not differentiated. Moreover, numerous associations were obtained between plasma selenoproteins and gut microbes. Se-supplementation partially antagonizes the gut microbiota alteration caused by Abx, and slightly by CC, but strongly altered profiles were observed in CC-Abx-Se, suggesting synergistic deleterious effects between pollutants, Abx and Se. Moreover, although CC and Abx changed gut microbiota, several common taxa were enriched in CC-Abx and control mice, indicating possible synergistic effects. Our results suggest a potential beneficial impact of supplementation, but mediated by gut microbes being reversed in their absence.

Mice brain metabolomics after the exposure to a "chemical cocktail" and selenium supplementation through the gut-brain axis

Several environmental pollutants have been shown to damage brain and affect gut microbiota. Limited evidence is available about the impact of "chemical cocktails" (CC) of xenobiotics on brain metabolome and their possible influence in the gut-brain crosstalk. To this end, BALB/c mice were exposed to heavy metals (As, Hg, Cd) and pharmaceuticals (diclofenac and flumequine) under regular rodent diet or supplemented with selenium (Se). Selenium, an antioxidant well-known for its antagonism against the neurotoxicity of several pollutants, modulated several brain metabolic impairments caused by CC (e.g., brain levels of the excitatory amino acid N-acetyl aspartic acid) by influencing mainly the metabolisms of purine, glycosylate and dicarboxylate, glutamate, glycerophospholipid, alanine and aspartate. Numerous associations were obtained between brain metabolites and gut microbes and they changed after Se-supplementation (e.g., Lactobacillus was positively associated with a brain ceramide, phosphoserine, phosphocholine, vitamin D3 derivative, fatty acids, malic acid, amino acids, and urea after the exposure, but not after Se-supplementation). Our results showed numerous evidences about the impact of CC on brain metabolome, the potential role of Se as an antagonist and their impact on the gut-brain axis. Further research is needed to understand the complex mechanism of action implied on CC-brain-microbiota interactions.

A review of the impact of xenobiotics from dietary sources on infant health: Early life exposures and the role of the microbiota

Xenobiotics are worldwide distributed and humans are unavoidably exposed to multiple chemical compounds during life, from preconception to adulthood. The human microbiota is mainly settled during early life and modulate host health and fitness. One of the main routes for chemical exposure is by intake of contaminated food and water. Thus, the interplay between diet-xenobiotics-microbiota during pregnancy and perinatal period may have relevant consequences for infant and adult health. Maternal exposure to metal(oid)s, persistent organic pollutants, and some food additives can modify the infant's microbiota with unknown consequences for child or adult health. Toxicants' exposure may also modulate the maternal transfer of microorganisms to the progeny during birth and breastfeeding; however, scarce information is available. The rapid increase in releasing novel chemicals to the environment, the exposure to chemical mixtures, the chronic/low dose scenario, and the delay in science-stakeholders action call for novel and groundbreaking approaches to improve a comprehensive risk assessment in sensitive population groups like pregnant women and neonates, with emphasis on microbiota as modulating factor and target-organ of xenobiotic's toxicity.

Perinatal environment shapes microbiota colonization and infant growth: impact on host response and intestinal function

BACKGROUND

Early microbial colonization triggers processes that result in intestinal maturation and immune priming. Perinatal factors, especially those associated with birth, including both mode and place of delivery are critical to shaping the infant gut microbiota with potential health consequences.

METHODS

Gut microbiota profile of 180 healthy infants (n = 23 born at home and n = 157 born in hospital, 41.7% via cesarean section [CS]) was analyzed by 16S rRNA gene sequencing at birth, 7 days, and 1 month of life. Breastfeeding habits and infant clinical data, including length, weight, and antibiotic exposure, were collected up to 18 months of life. Long-term personalized in vitro models of the intestinal epithelium and innate immune system were used to assess the link between gut microbiota composition, intestinal function, and immune response.

RESULTS

Microbiota profiles were shaped by the place and mode of delivery, and they had a distinct biological impact on the immune response and intestinal function in epithelial/immune cell models. Bacteroidetes and Bifidobacterium genus were decreased in C-section infants, who showed higher z-scores BMI and W/L during the first 18 months of life. Intestinal simulated epithelium had a stronger epithelial barrier function and intestinal maturation, alongside a higher immunological response (TLR4 route activation and pro-inflammatory cytokine release), when exposed to home-birth fecal supernatants, compared with CS. Distinct host response could be associated with different microbiota profiles.

CONCLUSIONS

Mode and place of birth influence the neonatal gut microbiota, likely shaping its interplay with the host through the maturation of the intestinal epithelium, regulation of the intestinal epithelial barrier, and control of the innate immune system during early life, which can affect the phenotypic responses linked to metabolic processes in infants.

TRIAL REGISTRATION

NCT03552939 . Video Abstract.

Maternal diet during pregnancy and intestinal markers are associated with early gut microbiota

BACKGROUND

Diet has an important role in host-microbiome interplay, which may result in intestinal permeability changes and physiopathological effects at a systemic level. Despite the importance of maternal microbiota as the main contributor to the initial microbial seeding, little is known about the effects of maternal diet during pregnancy on maternal-neonatal microbiota.

OBJECTIVES

This study aimed at ascertaining the possible associations between maternal dietary intake during pregnancy and neonatal microbiota at birth and to evaluate the relationship with maternal intestinal markers.

METHODS

In a nested cross-sectional study in the longitudinal MAMI cohort, maternal-neonatal microbiota profiling at birth (n = 73) was assessed by 16S rRNA gene sequencing. Maternal intestinal markers as zonulin, intestinal alkaline phosphatase (IAP) activity and faecal calprotectin were measured in faeces. Furthermore, maternal-neonatal clinical and anthropometric data, as well as maternal nutrient intake during pregnancy obtained by FFQ questionnaires, were collected.

RESULTS

Maternal diet is associated with both maternal and neonatal microbiota at the time of birth, in a delivery mode-dependent manner. The existing link between maternal diet, intestinal makers and neonatal gut microbiota would be mainly influenced by the intake of saturated (SFA) and monounsaturated fatty acids (MUFA). Members of Firmicutes in the neonatal microbiota were positively associated with maternal fat intake, especially SFA and MUFA, and negatively correlated to fibre, proteins from vegetable sources and vitamins.

CONCLUSIONS

Maternal diet during pregnancy, mainly fat intake (SFA and MUFA), was related to intestinal markers, thus likely shifting the microbial transmission to the neonate and priming the neonatal microbial profile with potential health outcomes.

CLINICAL TRIAL REGISTRY

NCT03552939.

Postbiotics: facts and open questions. A position paper on the need for a consensus definition

The past definitions of probiotics and prebiotics have been reviewed and updated recently. According to these concepts, probiotics comprise live microorganisms that confer a health benefit on the host when administered in adequate amounts, whereas a prebiotic is a substrate that is selectively utilised by host microorganisms, conferring a health benefit. The words probiotics and prebiotics can be found on labels of many foods and supplements. Consumers have a growing awareness of these terms' meanings, and many countries are increasingly using them for regulation purposes. At the same time, there is increasing evidence on the health effects of non-viable microorganisms and the metabolites that they can produce by fermentation or by their action on food components. Different terms have been used in the literature to refer to these bioactive compounds, which do not fall under the known categories of probiotics, prebiotics or synbiotics. The tentative term postbiotics has been the most used one so far. However, no definition of the term has gained international consensus to date. This work aims to provide information on the facts and the open questions about the so-called postbiotics.

Oral microbiota maturation during the first 7 years of life in relation to allergy development

BACKGROUND

Allergic diseases have become a major public health problem in affluent societies. Microbial colonization early in life seems to be critical for instructing regulation on immune system maturation and allergy development in children. Even though the oral cavity is the first site of encounter between a majority of foreign antigens and the immune system, the influence of oral bacteria on allergy development has not yet been reported.

OBJECTIVE

We sought to determine the bacterial composition in longitudinally collected saliva samples during childhood in relation to allergy development.

METHODS

Illumina sequencing of the 16S rDNA gene was used to characterize the oral bacterial composition in saliva samples collected at 3, 6, 12, 24 months, and 7 years of age from children developing allergic symptoms and sensitization (n = 47) and children staying healthy (n = 33) up to 7 years of age.

RESULTS

Children developing allergic disease, particularly asthma, had lower diversity of salivary bacteria together with highly divergent bacterial composition at 7 years of age, showing a clearly altered oral microbiota in these individuals, likely as a consequence of an impaired immune system during infancy. Moreover, the relative amounts of several bacterial species, including increased abundance of Gemella haemolysans in children developing allergies and Lactobacillus gasseri and L. crispatus in healthy children, were distinctive during early infancy, likely influencing early immune maturation.

CONCLUSION

Early changes in oral microbial composition seem to influence immune maturation and allergy development. Future experiments should test the probiotic potential of L. gasseri and L. crispatus isolates.

Impact of Fishmeal Replacement in Diets for Gilthead Sea Bream (Sparus aurata) on the Gastrointestinal Microbiota Determined by Pyrosequencing the 16S rRNA Gene

Recent studies have demonstrated the impact of diet on microbiota composition, but the essential need for the optimization of production rates and costs forces farms and aquaculture production to carry out continuous dietary tests. In order to understand the effect of total fishmeal replacement by vegetable-based feed in the sea bream (Sparus aurata), the microbial composition of the stomach, foregut, midgut and hindgut was analysed using high-throughput 16S rDNA sequencing, also considering parameters of growth, survival and nutrient utilisation indices.A total of 91,539 16S rRNA filtered-sequences were analysed, with an average number of 3661.56 taxonomically assigned, high-quality sequences per sample. The dominant phyla throughout the whole gastrointestinal tract were Actinobacteria, Protebacteria and Firmicutes. A lower diversity in the stomach in comparison to the other intestinal sections was observed. The microbial composition of the Recirculating Aquaculture System was totally different to that of the sea bream gastrointestinal tract. Total fishmeal replacement had an important impact on microbial profiles but not on diversity. Streptococcus (p-value: 0.043) and Photobacterium (p-value: 0.025) were highly represented in fish fed with fishmeal and vegetable-meal diets, respectively. In the stomach samples with the vegetable diet, reads of chloroplasts and mitochondria from vegetable dietary ingredients were rather abundant. Principal Coordinate Analysis showed a clear differentiation between diets in the microbiota present in the gut, supporting the presence of specific bacterial consortia associated with the diet.Although differences in growth and nutritive parameters were not observed, a negative effect of the vegetable diet on the survival rate was determined. Further studies are required to shed more light on the relationship between the immune system and sea bream gastrointestinal tract microbiota and should consider the modulation of the microbiota to improve the survival rate and nutritive efficacy when using plant-based diets.

Role of probiotics in reducing the risk of gestational diabetes

Overweight and obesity currently constitute a major threat to human well-being. Almost half of the female population are currently overweight. Pregnant overweight women are at risk of gestational diabetes affecting the health of the mother and the child, in both the short and long term. Notwithstanding the extensive scientific interest centred on the problem, research efforts have thus far been unable to devise preventive strategies. Recent scientific advances point to a gut microbiota dysbiosis, with ensuing low-grade inflammation as a contributing element, in obesity and its comorbidities. Such findings would suggest a role for specific probiotics in the search for preventive and therapeutic adjunct applications in gestational diabetes. The aim of the present paper was to critically review recent demonstrations of the role of intestinal microbes in immune and metabolic regulation, which could be exploited in nutritional management of pregnant women by probiotic bacteria. By modulating specific target functions, probiotic dietary intervention may exert clinical effects beyond the nutritional impact of food. As this approach in pregnancy is new, an overview of the role of gut microbiota in shaping host metabolism, together with the definition of probiotics are presented, and finally, specific targets and potential mechanisms for probiotics in pregnancy are discussed. Pregnancy appears to be the most critical stage for interventions aiming to reduce the risk of non-communicable disease in future generations, beyond the immediate dangers attributable to the health of the mother, labour and the neonate. Specific probiotic interventions during pregnancy provide an opportunity, therefore, to promote the health not only of the mother but also of the child.

Understanding gut microbiota in elderly's health will enable intervention through probiotics

Today, advances in the public health system of most countries have managed to extend notably life expectancy, however, elderly's health remain as a very serious concern. The lifelong stimulation of innate and adaptive immune systems leads to immunosenescence and, as result, to a low ability to produce immunoglobulins against pathogens but also to a low-grade chronic inflammatory state (inflammaging) that is linked to most age-related health problems, such as dementia, Alzheimer or atherosclerosis. This inflammatory state could make the host more sensitive to intestinal microbes, or vice versa, as changes in the gut microbiota composition are related to the progression of diseases and frailty in the elderly population. It was considered that gut microbiota changed during aging, with an increase of Bacteroidetes vs. Firmicutes proportion and a reduction of bifidobacterial counts, however recent studies reported a great inter-individual variation among elderly and a significant relationship between gut microbiota, diet and institution or community living. Intervention studies of probiotics and prebiotics in elderly are not very abundant, but most cases showed that Bifidobacterium populations can efficiently be stimulated with a concomitant decrease of Enterobacteria. Furthermore, also some studies demonstrated that probiotics decreased the synthesis of pro-inflammatory cytokines which are upregulated in the elderly, such as interleukin (IL)-8, IL-6 or tumour necrosis factor ?, among others, and they increased the levels of activated lymphocytes, natural killer cells, phagocytic activity and even showed a greater response to influenza vaccination. This suggests that direct manipulation of the gut microbiota may improve adaptive immune response and reduce inflammatory secretions, therefore compensating immunosenescence effects, however, there are no records of their effect on clinical symptoms or risk for disease. Those facts reveal that this is an open research field with very good scientific perspectives and above all they could bring likely improvements in the wellbeing of our seniors.

Microbial mucosal colonic shifts associated with the development of colorectal cancer reveal the presence of different bacterial and archaeal biomarkers

BACKGROUND

Epidemiological studies demonstrate a link between gastrointestinal cancers and environmental factors such as diet. It has been suggested that environmental cancer risk is determined by the interaction between diet and microbes. Thus, the purpose of this study was to examine the hypothesis that microbiota composition during colorectal cancer (CRC) progression might differ depending on the stage of the disease.

METHODS

A total of 28 age-matched and sex-matched subjects, seven with CRC adenocarcinoma, 11 with tubular adenomas and ten healthy subjects with intact colon, were included into the study. Microbiomes from mucosal and fecal samples were analyzed with 16S ribosomal RNA gene pyrosequencing, together with quantitative PCR of specific bacteria and archaea.

RESULTS

The principal coordinates analysis clearly separated healthy tissue samples from polyps and tumors, supporting the presence of specific bacterial consortia that are associated with affected sites and that can serve as potential biomarkers of CRC progression. A higher presence of Fusobacterium nucleatum and Enterobacteriaceae was found by qPCR in samples from CRC compared to healthy controls. We observed a correlation between CRC process development and levels of Methanobacteriales (R = 0.537, P = 0.007) and Methanobrevibacterium (R = 0.574, P = 0.03) in fecal samples.

CONCLUSION

Differences in microbial and archaeal composition between mucosal samples from healthy and disease tissues were observed in tubular adenoma and adenocarcinoma. In addition, microbiota from mucosal samples represented the underlying dysbiosis, whereas fecal samples seem not to be appropriate to detect shifts in microbial composition. CRC risk is influenced by microbial composition, showing differences according to disease progression step and tumor severity.

Pathogen exclusion properties of canine probiotics are influenced by the growth media and physical treatments simulating industrial processes

AIMS

Manufacturing process used in preparation of probiotic products may alter beneficial properties of probiotics. The effect of different growth media and inactivation methods on the protective properties of canine-originated probiotic bacteria against adhesion of canine enteropathogens was investigated.

METHODS AND RESULTS

Three established dog probiotics, Lactobacillus fermentum VET9A, Lactobacillus plantarum VET14A and Lactobacillus rhamnosus VET16A, and their mixture were assessed using the dog mucus pathogen exclusion model. The pathogens used were Enterococcus canis, Salmonella enterica serovar Typhimurium and Clostridium perfringens. The effect of growth media, one reflecting laboratory and the other manufacture conditions, and viability (viable and heat inactivated, 80°C per 30 min) on the pathogen exclusion properties of probiotics were characterized. Greater pathogen exclusion percentages were noted for probiotics growing in conditions reflecting manufacture when compared to laboratory (P < 0·05). Inactivation of probiotics by heat (80°C per 30 min) increased pathogen exclusion compared with their viable forms (P < 0·05).

CONCLUSIONS

Manufacturing process conditions such as growth media, incubation temperature and pretreatment methods may significantly affect the protective properties of the tested strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

Growing conditions and pretreatment methods should be carefully considered when designing new probiotics to reduce the risk of common infections in dogs. The studied probiotics are promising potential feed additives for dogs.

The effect of growth media and physical treatments on the adhesion properties of canine probiotics

AIMS

The manufacturing processes have been reported to influence the properties of probiotics with potential impact on health properties. The aim was to investigate the effect of different growth media and inactivation methods on the properties of canine-originated probiotic bacteria alone and in combination mixture.

METHODS AND RESULTS

Three established dog probiotics, Lactobacillus fermentum VET9A, Lactobacillus plantarum VET14A and Lactobacillus rhamnosus VET16A, and their combination mixture were evaluated for their adhesion to dog mucus. The effect of different growth media, one reflecting laboratory and the other manufacturing conditions, and inactivation methods (95°C, 80°C and UV irradiation) on the mucus adhesion of the probiotic strains was characterized. Evaluation of dog probiotics was supported by cell visualization using transmission electron microscopy (TEM). Higher adhesion percentage was reported for probiotic strains growing in laboratory rather than in manufacturing conditions (P < 0.05). Inactivation by heat (95°C, 80°C) decreased the adhesion properties when strains were cultivated in soy-based growth media compared with those grown in MRS broth (P < 0.05). TEM observations uncovered differences in cell-surface components in nonviable forms of probiotic strains as compared with their viable forms.

CONCLUSIONS

Manufacturing process conditions such as growth media and pretreatment methods may significantly affect the adhesive ability of the tested strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

Growth conditions, growth media, pretreatment methods and different probiotic combinations should be carefully considered for quality control of existing probiotics and for identification of new probiotics for dogs. These may also have an impact on health benefits for the host.

Early nutritional environment: focus on health effects of microbiota and probiotics

Balanced maternal nutrition during pregnancy ensures both the growth and development of the foetus and the well-being of the mother. Recent evidence supports the programming theory, which envisages long-lasting effects on later risk of chronic life-style-related diseases by early nutrition. The increasing problem of overweight, affecting almost half of the female population in Western societies, sets off adverse programming effects in the offspring manifested in subsequent health effects. To combat this problem, new tools involving life-style modifications are being actively sought to increment the traditional approaches. Immunonutrition, the ability of nutrients to influence the activities of cells in the immune system, may be one answer in combating low-grade systemic inflammation, the key underlying determinant in the obesity epidemic. Further, microbial compounds possess immunomodulatory properties which may be utilised to improve immune responses in clinically meaningful ways. Aberrant microbiota compositions have been detected during critical periods when early programming occurs, including pregnancy and infancy. Such alterations may regulate the health of the infant and the risk of subsequent disease, as demonstrated by the divergence in gut microbiota composition between healthy and overweight individuals. It may thus be hypothesised that the composition of the gut microbiota could be used as a target for intervention. Probiotics interact with the mucosal immune system via the same pathways as commensal bacteria to influence both innate and adaptive immune responses. In consequence, interventions with immunomodulatory diets, including certain nutrients and probiotics, may be critical in coordinating the adaptive function necessary for the formation of tolerance and thus in the prevention of undesirable metabolic consequences.

Assessment of the bacterial diversity of breast milk of healthy women by quantitative real-time PCR

AIMS

Breast milk has been described as a source of bacteria influencing the development of the infant gut microbiota. Up to the present, few studies have been focused on the application of culture-independent techniques to study bacterial diversity in breast milk. In this context, the aim of this study was to characterize the breast milk microbiota of healthy women by applying the quantitative real-time PCR technique (qRTi-PCR).

METHODS AND RESULTS

A total of 50 breast milk samples were analysed by qPCR to assess the presence of different bacterial genera or clusters, including the Bifidobacterium, Lactobacillus, Staphylococcus, Bacteroides, Enterococcus, Streptococcus, Clostridium cluster IV and Clostridium cluster XIVa-XIVb groups. Staphylococcus, Streptococcus, Bifidobacterium and Lactobacillus were the predominant groups and were detected in all the samples. Clostridium XIVa-XIVb and Enterococcus were detected in most of the samples in contrast to the Bacteroides and Clostridium cluster IV groups.

CONCLUSIONS

Our results confirm the abundance of bacterial DNA in breast milk samples and suggest that the qRTi-PCR technique has a huge potential in the microbiological analysis of human milk.

SIGNIFICANCE AND IMPACT OF THE STUDY

qRTi-PCR allowed the detection of bacterial DNA of streptococci, staphylococci, lactic acid bacteria and bifidobacteria in the samples of human milk, which confirms that breast milk can be an important source of bacteria and bacterial DNA to the infant gut.

Specific duodenal and faecal bacterial groups associated with paediatric coeliac disease

AIMS

To identify specific gut bacteria associated with coeliac disease (CD) at diagnosis and after treatment with a gluten-free diet (GFD) in a paediatric population.

METHODS

30 and 18 faecal samples from untreated and treated CD patients and 25 and 8 biopsy samples from untreated and treated CD patients, respectively, were analysed. In addition, 30 faecal and 8 biopsy samples from control children were evaluated for comparative purposes. Gut bacterial groups were quantified by real-time PCR.

RESULTS

Bacteroides and Clostridium leptum groups were more abundant in faeces and biopsies of CD patients than in controls regardless of the stage of the disease. E coli and Staphylococcus counts were also higher in faeces and biopsies of non-treated CD patients than in those of controls, but their levels were normalised after treatment with a GFD. Bifidobacterium levels were lower in faeces of both groups of CD patients and in biopsies of untreated CD patients compared to controls. Similar bacterial groups were related to CD in biopsies and faeces, indicating that faecal microbiota partly reflects that of the small intestine in CD patients, and could constitute a convenient biological index of this disorder.

CONCLUSIONS

Duodenal and faecal microbiota is unbalanced in children with untreated CD and only partially restored after long-term treatment with a GFD, constituting a novel factor linked to this disorder.

Induction of acid resistance in Bifidobacterium: a mechanism for improving desirable traits of potentially probiotic strains

AIMS

To generate stable acid-resistant Bifidobacterium strains isolated from human subjects and characterize the phenotypic changes of the acid-resistant derivatives.

METHODS AND RESULTS

The ability of 20 Bifidobacterium strains isolated from human faeces to survive to simulated gastrointestinal transit was evaluated, showing major reductions in viability (0.25-5.8 logarithmic units) because of gastric stress conditions. Six acid-sensitive strains belonging to the species Bifidobacterium longum and Bifidobacterium catenulatum were submitted to prolonged incubation at pH 2.0 to generate acid-resistant strains. The acid-sensitive and acid-resistant derivative strains were characterized to determine the changes associated with the acquisition of an acid-tolerant phenotype. The acid-resistant derivatives showed better ability to grow in the presence of bile salt (1-3%) and NaCl (6-10%) and higher resistance at elevated temperatures (60-70 degrees C, 10 min) than the parental strains. The acid-resistant derivatives displayed higher fermentative ability, and enzymatic activities. These strains also showed higher sensitivity to most of the tested antibiotics than the parental strains.

CONCLUSIONS

The stress tolerance of B. longum and B. catenulatum strains was improved by prolonged exposure to acid stress conditions. Some of the generated strains also seemed to have enhanced metabolic properties of relevance for probiotic applications.

SIGNIFICANCE AND IMPACT OF THE STUDY

The successful use of prolonged exposures to acid stress to improve the stability of human bifidobacteria indicates that this strategy could be useful for the production of robust probiotic strains, but involves other phenotypic changes that required an individual characterization.

Combining strains of lactic acid bacteria may reduce their toxin and heavy metal removal efficiency from aqueous solution

AIMS

The primary objective of this study was to compare the removal of cadmium, lead, aflatoxin B1 and microcystin-LR from aqueous solution by Lactobacillus rhamnosus GG, L. rhamnosus LC705, Propionibacterium freudenreichii shermanii JS and Bifidobacterium breve Bbi99/E8, separately and in combination.

METHODS AND RESULTS

The removal of toxins and heavy metals was assessed in batch experiments. The removal of all compounds was observed to be strain specific. The removal of lead by a combination of all the strains used was observed to be lower than could be predicted from the removal by single strains (P < 0.05). A similar trend was also observed with the other compounds studied.

CONCLUSIONS

The results show that the toxin-removal capacity of a combination of strains of lactic acid bacteria is not the sum of their individual capacities. Therefore, pure single strains should be used when the goal is to remove single compounds. The use of combinations of strains may be beneficial when several compounds are removed together. This needs to be studied in future experiments.

SIGNIFICANCE AND IMPACT OF THE STUDY

Lactic acid bacteria have been identified as potent tools for the decontamination of heavy metals, cyanotoxins and mycotoxins. The results of this study should be considered when selecting combinations of bacteria for the simultaneous removal of several toxic compounds.

Role of commercial probiotic strains against human pathogen adhesion to intestinal mucus

AIMS

The aims of this study present were to assess and to evaluate in vitro the abilities of commercial probiotic strains derived from fermented milk products and related sources currently marketed in European countries, to inhibit, compete and displace the adhesion of selected potential pathogens to immobilized human mucus.

METHODS AND RESULTS

The adhesion was assessed by measuring the radioactivity of bacteria adhered to the human mucus. We tested 12 probiotic strains against eight selected pathogens. All strains tested were able to adhere to mucus. All probiotic strains tested were able to inhibit and displace (P<0.05) the adhesion of Bacteroides, Clostridium, Staphylococcus and Enterobacter. In addition, the abilities to inhibit and to displace adhered pathogens depended on both the probiotic and the pathogen strains tested suggesting that several complementary mechanisms are implied in the processes.

CONCLUSIONS

Our results indicate the need for a case-by-case assessment in order to select strains with the ability to inhibit or displace a specific pathogen. Probiotics could be useful to correct deviations observed in intestinal microbiota associated with specific diseases and also, to prevent pathogen infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

The competitive exclusion properties of probiotics as well as their ability to displace and inhibit pathogens are the most importance for therapeutic manipulation of the enteric microbiota. The application of such strategies could contribute to expand the beneficial properties on human health against pathogen infection.

Probiotic Strains and Their Combination Inhibit In Vitro Adhesion of Pathogens to Pig Intestinal Mucosa

The aim of this study was to investigate in vitro the protective effect of commercial probiotic strains (Bifidobacterium lactis Bb12 and Lactobacillus rhamnosus LGG) alone and in combination on the adhesion of pathogenic strains as Salmonella, Clostridium, and Escherichia coli to pig intestinal mucus obtained from different intestinal regions. In combination, probiotic strains enhanced each other's adhesion, mainly in large intestinal mucus. Treatment of intestinal mucus with Bb12 and LGG, alone or in combination, significantly reduced (P < 0.05) the adhesion of the tested pathogens. The ability to inhibit pathogen adhesion appears to depend on the specific probiotics and pathogens and on the mucosal site. B. lactis Bb12 and L. rhamnosus LGG in combination revealed a better ability to inhibit adhesion of all pathogens tested to pig intestinal mucus than probiotic strains. Probiotic combinations could be useful for counteracting disease-associated aberrations in intestinal microbiota. Specific protective probiotics could be selected for particular pig pathogens. Probiotic strains from human origin and intended for human use also adhere to pig intestinal mucus and are able to displace and inhibit pathogens.

Development of New Probiotics by Strain Combinations: Is It Possible to Improve the Adhesion to Intestinal Mucus?

We evaluated the ability of commercial probiotic strains (Lactobacillus rhamnosus GG, L. rhamnosus LC705, Bifidobacterium breve 99, and Propionibacterium freudenreichii ssp. shermanii JS) to adhere alone or in different combinations to immobilized mucus. Probiotic combinations were clearly able to enhance the adhesion of L. rhamnosus GG, L. rhamnosus LC705, and P. freudenreichii ssp. shermanii JS. For L. rhamnosus GG and P. freudenreichii JS, all the combinations significantly improved adhesion to intestinal mucus, from 29.7 to 34.9% and from 1.9 to 2.3%, respectively. The adhesion of L. rhamnosus LC705 was improved from 0 to 46.4%. The adhesion of B. breve 99 was improved only in combination with L. rhamnosus GG and P. freudenreichii JS. Our results suggest that probiotic combinations could increase the beneficial health effects as compared with individual strains. Combinations of probiotic strains may therefore have synergistic adhesion effects, and such combinations also should be assessed in clinical studies.

Antimicrobial peptides are among the antagonistic metabolites produced by Bifidobacterium against Helicobacter pylori

Sixty acid-resistant Bifidobacterium isolates were recovered from human faeces and identified by genus-specific PCR and RAPD-PCR. Helicobacter pylori strains were isolated from gastric biopsies and identified by species-specific PCR. Twenty-four of the 60 Bifidobacterium isolates were considered to be different strains by RAPD-PCR. Six of the twenty-four different strains were shown to inhibit H. pylori. These antagonistic effects were related to heat-stable proteinaceous compounds, resistant to heating at 100 degrees C for 10 min, but sensitive to proteases. H. pylori stains showed variable resistance to therapeutic antibiotics (metronidazole and clarithromycin), while all the selected bifidobacteria showed intrinsic resistance to metronidazole. These potentially probiotic bifidobacteria were able to inhibit the growth of both antibiotic sensitive and resistant H. pylori strains. Thus, the synthesis of antimicrobial peptides could be one of the mechanisms of bifidobacteria to combat H. pylori infections.

Note. In Vitro Viability of Bifidobacterium Strains Isolated from Commercial Dairy Products Exposed to Human Gastrointestinal Conditions

Levels of bifidobacteria contained in commercial fermented milks in Spain were determined by fluorescent techniques. The transit tolerance of probiotic bifidobacteria strains to human gastrointestinal tract (GIT) was assessed in vitro. The number of bifidobacteria in commercial fermented milks declared to contain bifidobacteria varied from 104 to 107 bacteria/m L. Viable cell counts estimated by plating onto selective media were lower than direct counts. Bifidobacteriumstrains analysed showed different survival behaviour. Viable bacteria counts decreased considerably following exposure to gastric juice. As only intrinsic acid resistant cells survive their passage through the human intestine, the selection of acid tolerant strains is necessary for the elaboration of probiotic products. Viability of dairy bifidobacteria is affected by gastrointestinal juices but the majority of tested strains survived well at gastrointestinal conditions. The reason for this may be the low number of viable bifidobacteria contained in commercial dairy products. Adaptation and survival at low pH is likely to determine the efficacy of Bifidobacterium strains both as dairy starters and probiotic microorganisms. This study confirmed the usefulness of fluorescent techniques for a rapid and accurate evaluation of bacterial viability in probiotic products.

Functional and biochemical evidence for diazepam as a cyclic nucleotide phosphodiesterase type 4 inhibitor

1. The responses of the electrically-driven right ventricle strip of the guinea-pig heart to diazepam were recorded in the absence and in the presence of different selective cyclic nucleotide phosphodiesterase (PDE) inhibitors. 2. Diazepam, at concentrations ranging from 1 microM to 100 microM, was devoid of effect on the contractile force in this preparation. 3. Conversely, diazepam (5 microM-100 microM) produced a consistent positive inotropic response in the presence of a concentration (1 microM), that was without effect in the absence of diazepam, of either of the selective PDE 3 inhibitors milrinone or SK&F 94120, but not in the presence of the selective PDE 4 inhibitor rolipram. 4. This effect of diazepam was not gamma-aminobutyric acid (GABA)-dependent, since it was neither mimicked nor potentiated by GABA, and was not affected by either a high concentration (5 microM) of the antagonists of the benzodiazepine/GABA/channel chloride receptor complex, picrotoxin, flumazenil and beta-carboline-3-carboxylic acid methyl ester (betaCCMe), or by the inverse agonists, beta-carboline-3-carboxylic acid N-methylamide (betaCCMa) and methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM, 0.1 microM). Furthermore, a specific antagonist of the peripheral benzodiazepine receptors, PK 11195 (5 microM), did not influence the effect of diazepam. 5. Biochemical studies with isolated PDEs, confirmed that diazepam selectively inhibits type 4 PDE from guinea-pig right ventricle rather than the other PDEs present in that tissue. The compound inhibited this enzyme in a non-competitive manner. Diazepam was also able to inhibit PDE 5, the cyclic GMP specific PDE absent from cardiac muscle, with a potency close to that shown for PDE 4. 6. Diazepam displaced the selective type 4 PDE inhibitor, rolipram from its high affinity binding site in rat brain cortex membranes, and also potentiated the rise in cyclic AMP levels induced by isoprenaline in guinea-pig eosinophils, where only type 4 PDE is present. 7. The PDE inhibitory properties of diazepam were shared, although with lower potency, by other structurally-related benzodiazepines, that also displaced [3H]-rolipram from its high affinity binding site. The order of potency found for these compounds in these assays was not related to their potencies as modulators of the GABA receptor through its benzodiazepine binding site. 8. The pharmacological and biochemical data presented in this study indicate that diazepam behaves as a selective type 4 PDE inhibitor in cardiac tissue and this effect seems neither to be mediated by the benzodiazepine/GABA/channel chloride receptor complex nor by peripheral type benzodiazepine receptors.

Discrepancy between inotropic response and cyclic AMP production induced by isoprenaline and forskolin in rat ventricle strips

The effects of isoprenaline and forskolin were studied on contractile response and cyclic AMP levels in the right ventricle strips of the rat heart. Isoprenaline, in concentrations ranging from 10 nM to 1 microM, significantly increased, in a concentration-dependent manner, the contractile force in this preparation. Forskolin (1-10 microM), which directly stimulates adenylate cyclase, also produced a concentration-dependent increase in cardiac contractility. The mean EC50 (microM) for the contractile action of isoprenaline was 0.08 +/- 0.014 and that of forskolin 7.3 +/- 1.1 being about 70 times less potent than isoprenaline. However, isoprenaline (0.1 microM) and forskolin (8 microM), which produced about the same inotropic response, increased tissue cyclic AMP levels by about two and five fold respectively, when compared to the basal value. These figures further indicate that while the intracellular levels of cyclic AMP in rat ventricular myocardium may be an important determinant of positive inotropism, the connection between the two parameters is more complex than the simple ratio between the tension generated and the amount of cyclic AMP found inside the cells.

Diazepam potentiates the positive inotropic effect of isoprenaline in rat ventricle strips: role of cyclic AMP

The responses of the electrically driven right ventricle strip of the rat heart to isoprenaline and other cyclic AMP-related inotropic agents were recorded in the absence and in the presence of diazepam. Isoprenaline, in concentrations ranging from 10 nM to 1 microM, significantly increased, in a concentration-dependent manner, the contractile force in this preparation. Diazepam (10 microM) produced a leftward shift in the isoprenaline concentration-response curve and significantly reduced its EC50. Higher concentrations of diazepam (100 microM) produced no further shift, but reduced the maximum of the concentration-response curve of isoprenaline. Forskolin (0.5-10 microM), which directly stimulates adenyl cyclase, also produced a concentration-dependent increase in cardiac contractility. Diazepam (10 microM) displaced to the left the concentration-response curve for forskolin and reduced its EC50. The cyclic AMP analogous dibutyryl cyclic AMP (0.1-1 mM) produced concentration-dependent positive inotropic effects which were not significantly modified in the presence of diazepam (10 microM). Diazepam (10 microM) significantly enhanced the cyclic AMP production induced by isoprenaline (0.1 microM) and forskolin (10 microM) by about 136% and 35% respectively. These results indicate that diazepam potentiates the positive inotropic effect induced by beta-adrenoceptor agonists, probably by increasing cyclic AMP production induced by these agents.