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Direct-fed microbials (DFM) are considered as a promising technique to improve animal productivity without affecting animal health or harming the environment. The potential of three bacterial DFM to reduce methane (CH4) emissions, modulate ruminal fermentation, milk production and composition of primiparous dairy cows was examined in this study. As previous reports have shown that DFM respond differently to different diets, two contrasting diets were used in this study. Eight lactating primiparous cows were randomly divided into two groups that were fed a corn silage-based, high-starch diet (HSD) or a grass silage-based, high-fiber diet (HFD). Cows in each dietary group were randomly assigned to four treatments in a 4 × 4 Latin square design. The bacterial DFM used were selected for their proven CH4-reducing effect in vitro. Treatments included control (without DFM) and 3 DFM treatments: Propionibacterium freudenreichii 53-W (2.9 × 1010 colony forming units (CFU)/cow per day), Lactobacillus pentosus D31 (3.6 × 1011 CFU/cow per day) and Lactobacillus bulgaricus D1 (4.6 × 1010 CFU/cow per day). Each experimental period included 4 weeks of treatment and 1 week of wash-out, with measures performed in the fourth week of the treatment period. Enteric CH4 emissions were measured during 3 consecutive days using respiration chambers. Rumen samples were collected for ruminal fermentation parameters and quantitative microbial analyses. Milk samples were collected for composition analysis. Body weight of cows were recorded at the end of each treatment period. Irrespective of diet, no mitigating effect of DFM was observed on CH4 emissions in dairy cows. In contrast, Propionibacterium increased CH4 intensity by 27% (g CH4/kg milk) in cows fed HSD. There was no effect of DFM on other fermentation parameters and on bacterial, archaeal and protozoal numbers. Similarly, the effect of DFM on milk fatty acid composition was negligible. Propionibacterium and L. pentosus DFM tended to increase body weight gain with HSD. We conclude that, contrary to the effect previously observed in vitro, bacterial DFM Propionibacterium freudenreichii 53-W, Lactobacillus pentosus D31 and Lactobacillus bulgaricus D1 did not alter ruminal fermentation and failed to reduce CH4 emissions in lactating primiparous cows fed high-starch or high-fiber diets. Electronic supplementary material The online version of this article (10.1186/s40104-019-0342-9) contains supplementary material, which is available to authorized users.

ObjectiveTo systematically review the effect of oral intake of bacterial probiotics on 15 variables related to obesity, diabetes and non-alcoholic fatty liver disease.DesignSystematic review and meta-analysis.Data sourcesMedline, EMBASE and COCHRANE from 1990 to June 2018.Eligibility criteriaRandomised controlled trials (≥14 days) excluding hypercholesterolaemia, alcoholic liver disease, polycystic ovary syndrome and children ResultsOne hundred and five articles met inclusion criteria, representing 6826 subjects. In overweight but not obese subjects, probiotics induced improvements in: body weight (k=25 trials, d=−0.94 kg mean difference, 95% CI −1.17 to −0.70, I²=0.0%), body mass index (k=32, d=−0.55 kg/m², 95% CI −0.86 to −0.23, I²=91.9%), waist circumference (k=13, d=−1.31 cm, 95% CI −1.79 to −0.83, I²=14.5%), body fat mass (k=11, d=−0.96 kg, 95% CI −1.21 to −0.71, I²=0.0%) and visceral adipose tissue mass (k=5, d=−6.30 cm², 95% CI −9.05 to −3.56, I²=0.0%). In type 2 diabetics, probiotics reduced fasting glucose (k=19, d=−0.66 mmol/L, 95% CI −1.00 to −0.31, I²=27.7%), glycated haemoglobin (k=13, d=−0.28 pp, 95% CI −0.46 to −0.11, I²=54.1%), insulin (k=13, d=−1.66 mU/L, 95% CI −2.70 to −0.61, I²=37.8%) and homeostatic model of insulin resistance (k=10, d=−1.05 pp, 95% CI −1.48 to −0.61, I²=18.2%). In subjects with fatty liver diseases, probiotics reduced alanine (k=12, d=−10.2 U/L, 95% CI −14.3 to −6.0, I²=93.50%) and aspartate aminotransferases (k=10, d=−9.9 U/L, 95% CI −14.1 to -5.8, I²=96.1%). These improvements were mostly observed with bifidobacteria (Bifidobacterium breve, B. longum), Streptococcus salivarius subsp. thermophilus and lactobacilli (Lactobacillus acidophilus, L. casei, L. delbrueckii) containing mixtures and influenced by trials conducted in one country.ConclusionsThe intake of probiotics resulted in minor but consistent improvements in several metabolic risk factors in subjects with metabolic diseases.Trial registration numberCRD42016033273.

Vancomycin-resistant enterococci (VRE) represent major opportunistic pathogens in immunocompromised populations. Particularly adapted to the hospital environment, VRE efficiently colonize the gastrointestinal (GI) tract of patients. Furthermore, certain circumstances of antibiotic-induced dysbiosis of the gut microbiota contribute to colonization, overgrowth and persistence of VRE in the GI tract, increasing the risk of infection in critically ill and/or severally immunocompromised patients. VRE treatment with antibiotics remains challenging due to the robustness and ability of enterococci to adapt to harsh conditions and to acquire novel resistance genes. Reducing VRE intestinal colonization, overgrowth and carriage has thus become an important issue to reduce the risk of infection and dissemination. This review summarizes the knowledge of the conditions favoring VRE colonization and persistence in the GI tract and focuses on the strategies to reduce overgrowth or persistence of VRE in the GI tract based on the oral administration of probiotic or commensal bacteria in human studies and in animal models, and on the potential underlying mechanisms of the anti-VRE effect.