Probiotic yogurt and milk supplemented with probiotics have been investigated for their role in ‘low-grade’ inflammation but evidence for their efficacy is inconclusive. This study explores the impact of probiotic yogurt on metabolic and inflammatory biomarkers, with a parallel study of gut microbiota dynamics. The randomised cross-over study was conducted in fourteen healthy, young men to test probiotic yogurt compared with milk acidified with 2 %d-(+)-glucono-δ-lactone during a 2-week intervention (400 g/d). Fasting assessments, a high-fat meal test (HFM) and microbiota analyses were used to assess the intervention effects. Baseline assessments for the HFM were carried out after a run-in during which normal milk was provided. No significant differences in the inflammatory response to the HFM were observed after probiotic yogurt compared with acidified milk intake; however, both products were associated with significant reductions in the inflammatory response to the HFM compared with the baseline tests (assessed by IL6, TNFαand chemokine ligand 5) (P<0·001). These observations were accompanied by significant changes in microbiota taxa, including decreased abundance ofBilophila wadsworthiaafter acidified milk (log 2-fold-change (FC)=–1·5,P_adj=0·05) and probiotic yogurt intake (FC=–1·3,P_adj=0·03), increased abundance ofBifidobacteriumspecies after acidified milk intake (FC=1·4,P_adj=0·04) and detection ofLactobacillus delbrueckiispp.bulgaricus(FC=7·0,P_adj<0·01) andStreptococcus salivariusspp.thermophilus(FC=6·0,P_adj<0·01) after probiotic yogurt intake. Probiotic yogurt and acidified milk similarly reduce postprandial inflammation that is associated with a HFM while inducing distinct changes in the gut microbiota of healthy men. These observations could be relevant for dietary treatments that target ‘low-grade’ inflammation.

Antimicrobial susceptibility testing of microorganisms is performed by either disc diffusion or broth dilution tests. In clinical use, the tests are often still performed manually although automated systems exist. Most systems, however, are based on turbidometric methods which have well-known drawbacks.

Undefined starter cultures are poorly characterized bacterial communities from environmental origin used in cheese making. They are phenotypically stable and have evolved through domestication by repeated propagation in closed and highly controlled environments over centuries. This makes them interesting for understanding eco-evolutionary dynamics governing microbial communities. While cheese starter cultures are known to be dominated by a few bacterial species, little is known about the composition, functional relevance, and temporal dynamics of strain-level diversity. Here, we applied shotgun metagenomics to an important Swiss cheese starter culture and analyzed historical and experimental samples reflecting 82 years of starter culture propagation. We found that the bacterial community is highly stable and dominated by only a few coexisting strains of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. lactis. Genome sequencing, metabolomics analysis, and co-culturing experiments of 43 isolates show that these strains are functionally redundant, but differ tremendously in their phage resistance potential. Moreover, we identified two highly abundant Streptococcus phages that seem to stably coexist in the community without any negative impact on bacterial growth or strain persistence, and despite the presence of a large and diverse repertoire of matching CRISPR spacers. Our findings show that functionally equivalent strains can coexist in domesticated microbial communities and highlight an important role of bacteria-phage interactions that are different from kill-the-winner dynamics.

Background: Bifidobacteria are found at varying prevalence in human microbiota and seem to play an important role in the human gastrointestinal tract (GIT). Bifidobacteria are highly adapted to the human GIT which is reflected in the genome sequence of aBifidobacterim longumisolate. The competitiveness against other bacteria is not fully understood yet but may be related to the production of antimicrobial compounds such as bacteriocins. In a previous study, 34Bifidobacteriumisolates have been isolated from baby faeces among which six showed proteinaceous antilisterial activity againstListeria monocytogenes. In this study, one of these isolates, RBL67, was further identified and characterized.Results: Bifidobacteriumisolate RBL67 was classified and characterized using a polyphasic approach. RBL67 was classified asBifidobacterium thermophilumbased on phenotypic and DNA-DNA hybridization characteristics, although 16S rDNA analyses and partialgroEL sequences showed higher homology withB. thermacidophilumsubsp.porcinumandB. thermacidophilumsubsp.thermacidophilum, respectively. RBL67 was moderately oxygen-tolerant and was able to grow at pH 4 and at a temperature of 47°C.Conclusion: In order to assign RBL67 to a species, a polyphasic approach was used. This resulted in the classification of RBL67 as aBifidobacterium thermophilumstrain. To our knowledge, this is the first report aboutB. thermophilumisolated from baby faeces since theB. thermophilumstrains were related to ruminants and swine faeces before.B. thermophilumwas previously only isolated from animal sources and was therefore suggested to be used as differential species between animal and human contamination. Our findings may disapprove this suggestion and further studies are now conducted to determine whetherB. thermophilumis distributed broader in human faeces. Furthermore, the postulated differentiation between human and animal strains by growth above 45°C is no longer valid sinceB. thermophilumis able to grow at 47°C. In our study, 16S rDNA and partialgroEL sequence analysis were not able to clearly assign RBL67 to a species and were contradictory. Our study suggests that partialgroEL sequences may not be reliable as a single tool for species differentiation.

In this study, the use of isothermal microcalorimetry (IMC) for differentiation between methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) and MIC determination was evaluated. It was possible to differentiate between MRSA and MSSA within 4 h, whereas the standard method required 24 h. The MICs of cefoxitin were successfully determined for MRSA and MSSA by using IMC.

Background: Probiotic bacteria are thought to play an important role in the digestive system and therefore have to survive the passage from stomach to intestines. Recently, a novel approach to simulate the passage from stomach to intestines in a single bioreactor was developed. The advantage of this automated one reactor system was the ability to test the influence of acid, bile salts and pancreatin. Lactobacillus gasseri K7 is a strain isolated from infant faeces with properties making the strain interesting for cheese production. In this study, a single reactor system was used to evaluate the survival of L. gasseri K7 and selected bifidobacteria from our collection through the stomach-intestine passage. Results: Initial screening for acid resistance in acidified culture media showed a low tolerance of Bifidobacterium dentium for this condition indicating low survival in the passage. Similar results were achieved with B. longum subsp. infantis whereas B. animalis subsp. lactis had a high survival. These initial results were confirmed in the bioreactor model of the stomach-intestine passage. B. animalis subsp. lactis had the highest survival rate (10%) attaining approximately 5 × 10⁶ cfu ml^-1 compared to the other tested bifidobacteria strains which were reduced by a factor of up to 10⁶. Lactobacillus gasseri K7 was less resistant than B. animalis subsp. lactis but survived at cell concentrations approximately 1000 times higher than other bifidobacteria. Conclusion: In this study, we were able to show that L. gasseri K7 had a high survival rate in the stomach-intestine passage. By comparing the results with a previous study in piglets we could confirm the reliability of our simulation. Of the tested bifidobacteria strains, only B. animalis subsp. lactis showed acceptable survival for a successful passage in the simulation system.