Lachnospiraceae is a bacterial family usually isolated from human and mammalian intestinal microbiota. However, its presence and role in the infant microbiota is not fully elucidated. This may be due to the strictly anaerobic behavior of its members that hampers the possibility of culture-dependent enumeration. Here, we report on the presence of this bacterial group, using biomolecular techniques, in stool samples from 25 babies aged between 1 and 24 months. Denaturing gradient gel electrophoresis (DGGE) was used as a first detection step, and data were confirmed by quantitative PCR (qPCR). The DGGE showed the presence of Lachnospiraceae in infant fecal specimens and indicated the prevalence of Ruminococcus gnavus (R. gnavus). The qPCR confirmed the presence of the Clostridium XVIa group, Blautia genus, and R. gnavus, which are the main members of this family. We detected R. gnavus in 22 of 25 (88%) samples with a qPCR probe assay. Despite the difficulties associated with their detection and enumeration, Lachnospiraceae, and in particular R. gnavus, should be included in future studies on the infant microbiota composition.

Probiotics represent a possible strategy for controlling intestinal infections in livestock. Members of the Weissella genus are increasingly being studied for health-related applications in animals and humans. Here we investigated the functional properties of two Weissella cibaria strains isolated from cows reared in Kuwait breeding facilities by combining phenotypic with genomic analyses. W. cibaria SP7 and SP19 exhibited good growth in vitro under acidic conditions and in the presence of bile salts compared to the reference probiotic Lacticaseibacillus (formerly Lactobacillus) rhamnosus GG. Both strains were able to adhere to Caco-2 and HT-29 cell lines, as well as to mucin. The cell-free supernatants of the two isolates exhibited inhibitory activity towards Escherichia coli ATCC 25,922 and Salmonella enterica UC3605, which was ultimately due to the low pH of supernatants. W. cibaria SP19 showed a co-aggregation ability similar to that of L. rhamnosus GG when incubated with S. enterica. Whole genome sequencing and analysis revealed that both strains harbored several genes involved in carbohydrate metabolism and general stress responses, indicating bacterial adaptation to the gastrointestinal environment. We also detected genes involved in the adhesion to host epithelial cells or extracellular matrix. No evidence of acquired antibiotic resistance or hemolytic activity was found in either strain. These findings shed light on the potential of W. cibaria for probiotic use in livestock and on the mechanisms underlying host-microbe interaction in the gut. W. cibaria` strain SP19 exhibited the best combination of in vitro probiotic properties and genetic markers, and is a promising candidate for further investigation.

Delivery 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.

A growing body of clinical and experimental data supports the view that the efficacy of probiotics is strain-specific and restricted to particular pathological conditions, which means that newly isolated probiotic strains need to be targeted to a specific disease. Following national and international guidelines, we used a conventional in vitro experimental approach to characterize a novel strain of Lactobacillus reuteri, LMG P-27481, for safety (sensitivity to antibiotics and genome analysis) and putative efficacy (resistance to gastro-intestinal transit, adhesiveness, induction of cytokines, and release of antimicrobial metabolites). In vitro assays, which were carried out to examine the probiotic's effect on diarrhea (lactose utilization, inhibition of pathogens such as bacteria and Rotavirus), showed that it was more efficacious with respect to well-known reference strains in antagonizing Clostridioides difficile (CD). Data confirming that the probiotic can effectively treat CD colitis was gained from in vivo trials involving mice conditioned with large spectrum antibiotics before they were subjected to CD challenge. Two out of the three antibiotic-treated groups received daily LMG P-27481 for different time durations in order to simulate a preventive approach (LMG P-27481 administered prior to CD challenge) or an antagonistic one (LMG P-27481 administered after CD challenge). Both approaches significantly reduced, with respect to the untreated controls, CD DNA concentrations in caecum and C. difficile toxin titers in the gut lumen. In addition, LMG P-27481 supplementation significantly mitigated body weight loss and the extent of inflammatory infiltrate and tissue damage. The study results, which need to be confirmed by in vivo clinical trials, have demonstrated that the L. reuteri LMG P-27481 strain is a promising probiotic candidate for the treatment of CD infection.

The probiotic product consumption has recently increased with the prevalent intent to promote human and animal wellbeing. The complex selection process dealing with new-isolated probiotic candidates is the first challenge that has to be faced. From the isolation to the launch on the market, information about safety, tolerance to host physiological conditions, adhesion properties, genetics and interaction with the host has to be collected. Probiotics must be safe, survive to the exposition to bile salts and to gut transit, adhere to intestinal cells lining and colonize the lumen of the tract. The evaluation process of the possible probiotic health benefits is widely supported by in-vitro assays simulating the in-vivo conditions. The aim of this work is to summarize the classical models usually employed for the probiotic screening by underlying strengths and weaknesses of all models and to present some more recent analysis tools used in the probiotic field. The long term goal in new probiotic candidate selection experiencing these combined essays together would lead to the hypothetical assignment acknowledged as one strain-one function.