Metabolic characterization and viable delivery of Akkermansia muciniphila for its future application

The gut harbors a complex ecosystem in which many bacteria, both beneficial and pathogens, thrive. The potential importance of A. muciniphila as a member of the intestinal microbiota comes from the fact that A. muciniphila is reversely correlated with several diseases and reduce the fat mass gain of mice fed a high fat diet. We describe the use of genome-scale metabolic models to further understand the genetic and metabolic potential of microbiota members, as well as potential phenotypes and influence on the host. We emphasize the importance of culturing bacteria and provide an outline in which GEMs are used to aid in the development of minimal culture media. The use of GEMs for the development of minimal media was applied for A. muciniphila. We found that the essential components of A. muciniphila medium are L-threonine and either N-acetylglucosamine (GlcNAc) or N-acetylgalactosamine (GalNAc). The composition of the minimal medium was used to develop an animal component free medium. The addition of soy derived peptides increased the growth rate an yield, and the omission of animal components makes the cultured bacteria applicable in humans. We o analyzed the expression of the gene Amuc_1100, which was found to be involved in host signaling previously. There was no significant alteration in the expression of this genes, or genes in the associated gene cluster. In a subsequent experiment, we discovered that the anaerobic bacterium A. muciniphila is able to tolerate ambient . The addition of oxygen during growth increased the growth rate and yield, which was the result of cytochrome bd mediated oxygen reduction. To protect A. muciniphila during gastric passage, we encapsulated the cell in a water in oil in water double emulsion. We found a 100 fold higher survival of the encapsulated cells. We concluded that the double emulsion could be an effective matrix for the viable delivery of A. muciniphila. The final steps required for the application of A. muciniphila as therapeutic microbe are described shortly in the discussion, and are all within reach.</p

Bacteriological examination in place in five European countries to assess carcass fitness for consumption during meat inspection

In the European Union, bacteriological examination (BE) can be used as a decision support tool for an individual slaughter animal, if a clear decision regarding fitness for human consumption cannot be reached after performing the post-mortem meat inspection at the abattoir. The mandatory use of BE started already in the beginning of 20th century and the methods have since evolved in the different countries using it. Although still in use, discussions have taken place on whether BE is still a useful part of meat inspection. Currently, there is no European consensus regarding how to set up the methods or how to interpret the results. Still, there is a need to avoid unnecessary food waste, while at the same time guaranteeing food safety. In this descriptive study, we mapped the BE methods currently used in five European countries, namely Denmark, Finland, Germany, Italy and the Netherlands. The results show there is considerable variation between the countries regarding the specific analyses, sample matrices and media used. There is also variation in the indications when BE should be performed as well as when the results lead to condemnation. Although the results will be interpreted together with the pathological findings in the carcass, clearly written instructions should be available on how to interpret the results and when to perform condemnation. BE is used more often for cattle than for pigs, and e.g., in Denmark, BE is not used for pigs due to costs. Although BE can still be used to detect animals with a generalised infection at the time of slaughter, other methods that would be easier to standardise and accredit should be developed

More than just a gut feeling : constraint-based genome-scale metabolic models for predicting functions of human intestinal microbes

The human gut is colonized with a myriad of microbes, with substantial interpersonal variation. This complex ecosystem is an integral part of the gastrointestinal tract and plays a major role in the maintenance of homeostasis. Its dysfunction has been correlated to a wide array of diseases, but the understanding of causal mechanisms is hampered by the limited amount of cultured microbes, poor understanding of phenotypes, and the limited knowledge about interspecies interactions. Genome-scale metabolic models (GEMs) have been used in many different fields, ranging from metabolic engineering to the prediction of interspecies interactions. We provide showcase examples for the application of GEMs for gut microbes and focus on (i) the prediction of minimal, synthetic, or defined media; (ii) the prediction of possible functions and phenotypes; and (iii) the prediction of interspecies interactions. All three applications are key in understanding the role of individual species in the gut ecosystem as well as the role of the microbiota as a whole. Using GEMs in the described fashions has led to designs of minimal growth media, an increased understanding of microbial phenotypes and their influence on the host immune system, and dietary interventions to improve human health. Ultimately, an increased understanding of the gut ecosystem will enable targeted interventions in gut microbial composition to restore homeostasis and appropriate host-microbe crosstalk.Peer reviewe

Adaptation of Akkermansia muciniphila to the Oxic-Anoxic Interface of the Mucus Layer

Akkermansia muciniphila colonizes the mucus layer of the gastrointestinal tract, where the organism can be exposed to the oxygen that diffuses from epithelial cells. To understand how A. muciniphila is able to survive and grow at this oxic-anoxic interface, its oxygen tolerance and response and reduction capacities were studied. A. muciniphila was found to be oxygen tolerant. On top of this, under aerated conditions, A. muciniphila showed significant oxygen reduction capacities and its growth rate and yield were increased compared to those seen under strict anaerobic conditions. Transcriptome analysis revealed an initial oxygen stress response upon exposure to oxygen. Thereafter, genes related to respiration were expressed, including those coding for the cytochrome bd complex, which can function as a terminal oxidase. The functionality of A. muciniphila cytochrome bd genes was proven by successfully complementing cytochrome-deficient Escherichia coli strain ECOM4. We conclude that A. muciniphila can use oxygen when it is present at nanomolar concentrations. IMPORTANCE This article explains how Akkermansia muciniphila, previously described as a strictly anaerobic bacterium, is able to tolerate and even benefit from low levels of oxygen. Interestingly, we measured growth enhancement of A. muciniphila and changes in metabolism as a result of the oxygen exposure. In this article, we discuss similarities and differences of this oxygen-responsive mechanism with respect to those of other intestinal anaerobic isolates. Taken together, we think that these are valuable data that indicate how anaerobic intestinal colonizing bacteria can exploit low levels of oxygen present in the mucus layer and that our results have direct relevance for applicability, as addition of low oxygen concentrations could benefit the in vitro growth of certain anaerobic organisms.Peer reviewe

Translocation across a human enteroid monolayer by zoonotic Streptococcus suis correlates with the presence of Gb3-positive cells

Summary: Streptococcus suis is a zoonotic pathogen that can cause meningitis and septicaemia. The consumption of undercooked pig products is an important risk factor for zoonotic infections, suggesting an oral route of infection. In a human enteroid model, we show that the zoonotic CC1 genotype has a 40% higher translocation frequency than the non-zoonotic CC16 genotype. Translocation occurred without increasing the permeability or disrupting the adherens junctions and tight junctions of the epithelial monolayer. The translocation of zoonotic S. suis was correlated with the presence of Gb3-positive cells, a human glycolipid receptor found on Paneth cells and targeted by multiple enteric pathogens. The virulence factors Streptococcal adhesin Protein and suilysin, known to interact with Gb3, were not essential for translocation in our epithelial model. Thus, the ability to translocate across an enteroid monolayer correlates with S. suis core genome composition and the presence of Gb3-positive cells in the intestinal epithelium

Zoönosen, de publieke gezondheid en de huisarts

De afgelopen decennia is het risico op nieuwe of opnieuw opduikende infectieziekten toegenomen. In een niet-immune populatie kan dit voor grote medische, maatschappelijke en economische problemen zorgen. Driekwart van de nieuwe ziekteverwekkers komt van (wilde) dieren. Wanneer deze pathogenen vervolgens ook van mens tot mens overdraagbaar zijn, kan dit tot een pandemie leiden, zoals bij COVID-19 is gebeurd. Huisartsen kunnen als een van de eersten humane signalen van nieuwe infectieziekten oppikken. Daarmee spelen ze een belangrijke rol bij de vroegtijdige opsporing en bestrijding ervan

Zoönosen, de publieke gezondheid en de huisarts

De afgelopen decennia is het risico op nieuwe of opnieuw opduikende infectieziekten toegenomen. In een niet-immune populatie kan dit voor grote medische, maatschappelijke en economische problemen zorgen. Driekwart van de nieuwe ziekteverwekkers komt van (wilde) dieren. Wanneer deze pathogenen vervolgens ook van mens tot mens overdraagbaar zijn, kan dit tot een pandemie leiden, zoals bij COVID-19 is gebeurd. Huisartsen kunnen als een van de eersten humane signalen van nieuwe infectieziekten oppikken. Daarmee spelen ze een belangrijke rol bij de vroegtijdige opsporing en bestrijding ervan

Identification of Streptococcus suis putative zoonotic virulence factors: A systematic review and genomic meta-analysis

Streptococcus suis is an emerging zoonotic pathogen. Over 100 putative virulence factors have been described, but it is unclear to what extent these virulence factors could contribute to zoonotic potential of S. suis. We identified all S. suis virulence factors studied in experimental models of human origin in a systematic review and assessed their contribution to zoonotic potential in a subsequent genomic meta-analysis. PubMed and Scopus were searched for English-language articles that studied S. suis virulence published until 31 March 2021. Articles that analyzed a virulence factor by knockout mutation, purified protein, and/or recombinant protein in a model of human origin, were included. Data on virulence factor, strain characteristics, used human models and experimental outcomes were extracted. All publicly available S. suis genomes with available metadata on host, disease status and country of origin, were included in a genomic meta-analysis. We calculated the ratio of the prevalence of each virulence factor in human and pig isolates. We included 130 articles and 1703 S. suis genomes in the analysis. We identified 53 putative virulence factors that were encoded by genes which are part of the S. suis core genome and 26 factors that were at least twice as prevalent in human isolates as in pig isolates. Hhly3 and NisK/R were particularly enriched in human isolates, after stratification by genetic lineage and country of isolation. This systematic review and genomic meta-analysis have identified virulence factors that are likely to contribute to the zoonotic potential of S. suis

Erratum: Five Complete Genome Sequences Spanning the Dutch Streptococcus suis Serotype 2 and Serotype 9 Populations (Microbiology Resource Announcements (2022) 9:6 (e01439-19) DOI: 10.1128/MRA.01439-19)

Volume 9, no. 6, e01439-19, 2020, https://doi.org/10.1128/MRA.01439-19. Page 1, line 7: “CC20” should read “CC220.” Page 2, Table 1, line 3, column 4: “20” should read “220.” Page 2, Table 1, line 5, column 2: “Diseased pig” should read “Healthy pig.”