bims-bac4me 2023-08-27 papers

bims-bac4me

Biomed News

on Microbiome and trained immunity

Issue of 2023‒08‒27
twenty-one papers selected by
Chun-Chi Chang, University Hospital Zurich

Innate immune memory, trained immunity and nomenclature clarification.
Single Cell Transcriptomes, Lineage, and Differentiation of Functional Airway Microfold Cells.
Childhood Respiratory Viral Infections and the Microbiome.
Staphylococcus epidermidis activates keratinocyte cytokine expression and promotes skin inflammation through the production of phenol-soluble modulins.
Scarring the Early-Life Microbiome: Its Potential Life-long Effects on Human Health and Diseases.
Bacterial Metabolites and Inflammatory Skin Diseases.
S100A8/A9-alarmin promotes local myeloid-derived suppressor cell activation restricting severe autoimmune arthritis.
Trained immunity of alveolar macrophages enhances injury resolution via KLF4-MERTK-mediated efferocytosis.
Dual RNA-seq identifies genes and pathways modulated during Clostridioides difficile colonization.
The Calm after the Storm: Implications of Sepsis Immunoparalysis on Host Immunity.
Gut microbiota regulate migration of lymphocytes from gut to lung.
Activation of TLRs by Opportunistic Fungi in Lung Organoids.
A bacterial sialidase mediates early life colonization by a pioneering gut commensal.
Toll-like receptor 4 and Syk kinase shape dendritic cell-induced immune activation to major house dust mite allergens.
Reprogramming dendritic cells through the immunological synapse: A two-way street.
Bacteriophages targeting protective commensals impair resistance against Salmonella Typhimurium infection in gnotobiotic mice.
Synthetic microbial consortia for the treatment of Clostridioides difficile infection in mice model.
Bacterial multispecies interaction mechanisms dictate biogeographic arrangement between the oral commensals Corynebacterium matruchotii and Streptococcus mitis.
Multi-host infection and phylogenetically diverse lineages shape the recombination and gene pool dynamics of Staphylococcus aureus.
Host Soluble Factors Cause Changes in Staphylococcus epidermidis Antibiotic Susceptibility and Biofilm Formation Ability.
Dysregulated cross-talk between alveolar epithelial cells and stromal cells in idiopathic pulmonary fibrosis reduces epithelial regenerative capacity.

Nat Immunol. 2023 Sep;24(9): 1393-1394

Innate immune memory, trained immunity and nomenclature clarification.

George Hajishengallis, Mihai G Netea, Triantafyllos Chavakis.

DOI: https://doi.org/10.1038/s41590-023-01595-x
bioRxiv. 2023 Aug 07. pii: 2023.08.06.552176. [Epub ahead of print]

Single Cell Transcriptomes, Lineage, and Differentiation of Functional Airway Microfold Cells.

Manalee V Surve, Brian Lin, Jennifer L Reedy, Arianne J Crossen, Anthony Xu, Bruce S Klein, Jatin M Vyas, Jayaraj Rajagopal.

The airway epithelium is frequently exposed to pathogens and allergens, but the cells that are responsible for sampling these inhaled environmental agents have not been fully defined. Thus, there is a critical void in our understanding of how luminal antigens are delivered to the immune cells that drive the appropriate immune defenses against environmental assaults. In this study, we report the first single cell transcriptomes of airway Microfold (M) cells, whose gut counterparts have long been known for their antigen sampling abilities. Given their very recent discovery in the lower respiratory airways, the mechanisms governing the differentiation and functions of airway M cells are largely unknown. Here, we shed light on the pathways of airway M cell differentiation, establish their lineage, and identify a functional M cell-specific endocytic receptor, the complement receptor 2 (CR2). Lastly, we demonstrate that airway M cells can endocytose Aspergillus fumigatus conidia in a CR2-dependent manner. Collectively, this work lays a foundation for deepening our understanding of lung mucosal immunology and the mechanisms that drive lung immunity and tolerance.

DOI: https://doi.org/10.1101/2023.08.06.552176
J Allergy Clin Immunol. 2023 Aug 20. pii: S0091-6749(23)01060-6. [Epub ahead of print]

Childhood Respiratory Viral Infections and the Microbiome.

Kirsten M Kloepfer, Joshua L Kennedy.

  The human microbiome associated with the respiratory tract is diverse, heterogeneous, and dynamic. The diversity and complexity of the microbiome and the interactions between microorganisms, host cells, and the host immune system are complex and multifactorial. Furthermore, the lymphatics provide a direct highway, the gut-lung axis, for the gut microbiome to affect outcomes related to respiratory disease and the host immune response. Viral infections in the airways can also alter the presence or absence of bacterial species, which might increase the risks for allergies and asthma. Viruses infect the airway epithelium and interact with the host to promote inflammatory responses that can trigger a wheezing illness. This immune response may alter the host's immune response to microbes and allergens, leading to T2 inflammation. However, exposure to specific bacteria may also tailor the host's response long before the virus has infected the airway. The frequency of viral infections, age at infection, the sampling season, geographic location, population differences, and preexisting composition of the microbiota have all been linked to changes in microbiota diversity and stability. This review aims to evaluate the current reported evidence for microbiome interactions and the influences viral infection may have on respiratory and gut microbiota, affecting respiratory outcomes in children.

Keywords:  T2 inflammation; asthma; asthma exacerbations; gut-lung axis; microbiome; promotion of asthma; viral infection; wheezing

DOI:  https://doi.org/10.1016/j.jaci.2023.08.008
Cell Rep. 2023 Aug 22. pii: S2211-1247(23)01035-5. [Epub ahead of print]42(9): 113024

Staphylococcus epidermidis activates keratinocyte cytokine expression and promotes skin inflammation through the production of phenol-soluble modulins.

Michael R Williams, Michelle D Bagood, Timothy J Enroth, Zoie L Bunch, Nina Jiang, Edward Liu, Samia Almoughrabie, Shadi Khalil, Fengwu Li, Samantha Brinton, Nadja B Cech, Alexander R Horswill, Richard L Gallo.

  Staphylococcus epidermidis is a common microbe on human skin and has beneficial functions in the skin microbiome. However, under conditions of allergic inflammation, the abundance of S. epidermidis increases, establishing potential danger to the epidermis. To understand how this commensal may injure the host, we investigate phenol-soluble modulin (PSM) peptides produced by S. epidermidis that are similar to peptides produced by Staphylococcus aureus. Synthetic S. epidermidis PSMs induce expression of host defense genes and are cytotoxic to human keratinocytes. Deletion mutants of S. epidermidis lacking these gene products support these observations and further show that PSMs require the action of the EcpA bacterial protease to induce inflammation when applied on mouse skin with an intact stratum corneum. The expression of PSMδ from S. epidermidis is also found to correlate with disease severity in patients with atopic dermatitis. These observations show how S. epidermidis PSMs can promote skin inflammation.

Keywords:  CP: Immunology; CP: Microbiology; Staphylococcus; atopic dermatitis; inflammation; microbiome; phenol-soluble modulins; skin

DOI:  https://doi.org/10.1016/j.celrep.2023.113024
BMB Rep. 2023 Aug 22. pii: 5983. [Epub ahead of print]

Scarring the Early-Life Microbiome: Its Potential Life-long Effects on Human Health and Diseases.

Hyunji Park, Na-Young Park, Ara Koh.

The gut microbiome is widely recognized as a dynamic organ with a profound influence on human physiology and pathology. Extensive epidemiological and longitudinal cohort studies have provided compelling evidence that disruptions in the early-life microbiome can have long-lasting health implications. Various factors before, during, and after birth contribute to shaping the composition and function of the neonatal and infant microbiome. While these alterations can be partially restored over time, metabolic phenotypes may persist, necessitating research to identify the critical period for early intervention to achieve phenotypic recovery beyond microbiome composition. In this review, we provide current understanding of changes in the gut microbiota throughout life and the various factors affecting these changes. Specifically, we highlight the profound impact of early-life gut microbiota disruption on the development of diseases later in life and discuss perspectives on efforts to recover from such disruptions.
Metabolites. 2023 Aug 17. pii: 952. [Epub ahead of print]13(8):

Bacterial Metabolites and Inflammatory Skin Diseases.

Victoria Jiminez, Nabiha Yusuf.

  The microbiome and gut-skin axis are popular areas of interest in recent years concerning inflammatory skin diseases. While many bacterial species have been associated with commensalism of both the skin and gastrointestinal tract in certain disease states, less is known about specific bacterial metabolites that regulate host pathways and contribute to inflammation. Some of these metabolites include short chain fatty acids, amine, and tryptophan derivatives, and more that when dysregulated, have deleterious effects on cutaneous disease burden. This review aims to summarize the knowledge of wealth surrounding bacterial metabolites of the skin and gut and their role in immune homeostasis in inflammatory skin diseases such as atopic dermatitis, psoriasis, and hidradenitis suppurativa.

Keywords:  atopic dermatitis; bacterial metabolites; gut-skin axis; hidradenitis suppurativa; immune regulation; inflammatory skin disease; microbiome; psoriasis

DOI:  https://doi.org/10.3390/metabo13080952
Cell Rep. 2023 Aug 22. pii: S2211-1247(23)01017-3. [Epub ahead of print]42(8): 113006

S100A8/A9-alarmin promotes local myeloid-derived suppressor cell activation restricting severe autoimmune arthritis.

Meike von Wulffen, Veronika Luehrmann, Stefanie Robeck, Antonella Russo, Lena Fischer-Riepe, Martijn van den Bosch, Peter van Lent, Karin Loser, Dmitry I Gabrilovich, Sven Hermann, Johannes Roth, Thomas Vogl.

  Immune-suppressive effects of myeloid-derived suppressor cells (MDSCs) are well characterized during anti-tumor immunity. The complex mechanisms promoting MDSC development and their regulatory effects during autoimmune diseases are less understood. We demonstrate that the endogenous alarmin S100A8/A9 reprograms myeloid cells to a T cell suppressing phenotype during autoimmune arthritis. Treatment of myeloid precursors with S100-alarmins during differentiation induces MDSCs in a Toll-like receptor 4-dependent manner. Consequently, knockout of S100A8/A9 aggravates disease activity in collagen-induced arthritis due to a deficit of MDSCs in local lymph nodes, which could be corrected by adoptive transfer of S100-induced MDSCs. Blockade of MDSC function in vivo aggravates disease severity in arthritis. Therapeutic application of S100A8 induces MDSCs in vivo and suppresses the inflammatory phenotype of S100A9ko mice. Accordingly, the interplay of T cell-mediated autoimmunity with a defective innate immune regulation is crucial for autoimmune arthritis, which should be considered for future innovative therapeutic options.

Keywords:  CP: Immunology; MRP8/MRP14; S100A8/S100A9-induced MDSC; adoptive transfer of MDSC; arthritis; calprotectin

DOI:  https://doi.org/10.1016/j.celrep.2023.113006
J Exp Med. 2023 11 06. pii: e20221388. [Epub ahead of print]220(11):

Trained immunity of alveolar macrophages enhances injury resolution via KLF4-MERTK-mediated efferocytosis.

Sreeparna Chakraborty, Abhalaxmi Singh, Li Wang, Xinge Wang, Mark A Sanborn, Zijing Ye, Mark Maienschein-Cline, Amitabha Mukhopadhyay, Balaji B Ganesh, Asrar B Malik, Jalees Rehman.

Recent studies suggest that training of innate immune cells such as tissue-resident macrophages by repeated noxious stimuli can heighten host defense responses. However, it remains unclear whether trained immunity of tissue-resident macrophages also enhances injury resolution to counterbalance the heightened inflammatory responses. Here, we studied lung-resident alveolar macrophages (AMs) prechallenged with either the bacterial endotoxin or with Pseudomonas aeruginosa and observed that these trained AMs showed greater resilience to pathogen-induced cell death. Transcriptomic analysis and functional assays showed greater capacity of trained AMs for efferocytosis of cellular debris and injury resolution. Single-cell high-dimensional mass cytometry analysis and lineage tracing demonstrated that training induces an expansion of a MERTKhiMarcohiCD163+F4/80low lung-resident AM subset with a proresolving phenotype. Reprogrammed AMs upregulated expression of the efferocytosis receptor MERTK mediated by the transcription factor KLF4. Adoptive transfer of these trained AMs restricted inflammatory lung injury in recipient mice exposed to lethal P. aeruginosa. Thus, our study has identified a subset of tissue-resident trained macrophages that prevent hyperinflammation and restore tissue homeostasis following repeated pathogen challenges.

DOI: https://doi.org/10.1084/jem.20221388
mSystems. 2023 Aug 24. e0055523

Dual RNA-seq identifies genes and pathways modulated during Clostridioides difficile colonization.

Lucy R Frost, Richard Stark, Blessing O Anonye, Thomas O MacCreath, Ludmila R P Ferreira, Meera Unnikrishnan.

  The gastrointestinal pathogen Clostridioides difficile is the most common cause of hospital-acquired diarrhea. Bacterial interactions with the gut mucosa are crucial for the establishment of C. difficile infection; however, key infection events like bacterial attachment and gut penetration are still poorly defined. To better understand the initial events that occur when this anaerobe interacts with the human gut epithelium, we employed a dual RNA-sequencing approach to study the bacterial and host transcriptomic profiles during C. difficile infection in a dual environment in vitro human gut model. Temporal changes in gene expression during infection were studied in bacterial and epithelial cells over 3-24 hours. While there were several common differentially expressed bacterial genes across different timepoints after infection, mammalian transcriptional profiles were quite distinct, with little overlap. Interestingly, an induction of colonic receptors for C. difficile toxins was observed, along with the downregulation of genes encoding immune response markers. Several cell wall-associated proteins were downregulated in C. difficile when associated with host cells, including slpA, which encodes the main S-layer protein. Gene function and pathway enrichment analyses revealed a potential modulation of the purine/pyrimidine synthesis pathways both in the mammalian and bacterial cells. We observed that proline-proline endopeptidase, a secreted metalloprotease responsible for cell surface protein cleavage, is downregulated during infection, and a mutant lacking this enzyme demonstrated enhanced adhesion to epithelial cells during infection. This study provides new insight into the host and bacterial pathways based on gene expression modulation during the initial contact of C. difficile with gut cells. IMPORTANCE The initial interactions between the colonic epithelium and the bacterium are likely critical in the establishment of Clostridioides difficile infection, one of the major causes of hospital-acquired diarrhea worldwide. Molecular interactions between C. difficile and human gut cells have not been well defined mainly due to the technical challenges of studying cellular host-pathogen interactions with this anaerobe. Here we have examined transcriptional changes occurring in the pathogen and host cells during the initial 24 hours of infection. Our data indicate several changes in metabolic pathways and virulence-associated factors during the initial bacterium-host cell contact and early stages of infection. We describe canonical pathways enriched based on the expression profiles of a dual RNA sequencing in the host and bacterium, and functions of bacterial factors that are modulated during infection. This study thus provides fresh insight into the early C. difficile infection process.

Keywords:  Clostridioides difficile infection; dual RNA-seq; in vitro gut model; proline-proline endopeptidase

DOI:  https://doi.org/10.1128/msystems.00555-23
J Immunol. 2023 09 01. 211(5): 711-719

The Calm after the Storm: Implications of Sepsis Immunoparalysis on Host Immunity.

Elvia E Silva, Cara Skon-Hegg, Vladimir P Badovinac, Thomas S Griffith.

The immunological hallmarks of sepsis include the inflammation-mediated cytokine storm, apoptosis-driven lymphopenia, and prolonged immunoparalysis. Although early clinical efforts were focused on increasing the survival of patients through the first phase, studies are now shifting attention to the long-term effects of sepsis on immune fitness in survivors. In particular, the most pertinent task is deciphering how the immune system becomes suppressed, leading to increased incidence of secondary infections. In this review, we introduce the contribution of numerical changes and functional reprogramming within innate (NK cells, dendritic cells) and adaptive (T cells, B cells) immune cells on the chronic immune dysregulation in the septic murine and human host. We briefly discuss how prior immunological experience in murine models impacts sepsis severity, immune dysfunction, and clinical relevance. Finally, we dive into how comorbidities, specifically autoimmunity and cancer, can influence host susceptibility to sepsis and the associated immune dysfunction.

DOI: https://doi.org/10.4049/jimmunol.2300171
Microb Pathog. 2023 Aug 23. pii: S0882-4010(23)00344-3. [Epub ahead of print] 106311

Gut microbiota regulate migration of lymphocytes from gut to lung.

Silu Ni, Xiulei Yuan, Qihang Cao, Yiming Chen, Xingyu Peng, Jingyi Lin, Yanyan Li, Wentao Ma, Shikong Gao, Dekun Chen.

  The community of microorganisms known as gut microbiota that lives in the intestine confers significant health benefits on its host, primarily in the form of immunological homeostasis regulation. Gut microbiota not only can shape immune responses in the gut but also in other organs. This review focus on the gut-lung axis. Aberrant gut microbiota development is associated with greater lung disease susceptibility and respiratory disease induced by a variety of pathogenic bacteria. They are known to cause changes in gut microbiota. Recent research has found that immune cells in the intestine migrate to distant lung to exert anti-infective effects. Moreover, evidence indicates that the gut microbiota and their metabolites influence intestinal immune cells. Therefore, we suspect that intestine-derived immune cells may play a significant role against pulmonary pathogenic infections by receiving instructions from gut microbiota.

Keywords:  Gut microbiota; Gut-lung axis; Immune cell migration; Lung infection

DOI:  https://doi.org/10.1016/j.micpath.2023.106311
Methods Mol Biol. 2023 ;2700 271-284

Activation of TLRs by Opportunistic Fungi in Lung Organoids.

Veronika Bosáková, Jan Frič, Teresa Zelante.

  Organoid cultures may express several types of pattern-recognition receptors and in particular toll-like receptors, representing an extremely efficient and innovative system to understand how pathogen-associated molecular patterns exposure may affect the immunity, the growth, or differentiation of complex tissues. Here, we describe how to generate lung organoids from human-induced pluripotent stem cells. Three-dimensional (3D) cultures are then stimulated with different toll-like receptor ligands derived from fungi or with Aspergillus fumigatus. RNA sequencing may be performed upon organoid cultures to understand host-pathogen innate immune interactions.

Keywords:  Aspergillus fumigatus; Fungal infections; Fungi; Organoids; PGG; TLR; WGP; iPSC; β-glucan

DOI:  https://doi.org/10.1007/978-1-0716-3366-3_16
bioRxiv. 2023 Aug 09. pii: 2023.08.08.552477. [Epub ahead of print]

A bacterial sialidase mediates early life colonization by a pioneering gut commensal.

Ekaterina Buzun, Chia-Yun Hsu, Kristija Sejane, Renee E Oles, Adriana Vasquez Ayala, Luke R Loomis, Jiaqi Zhao, Leigh-Ana Rossitto, Dominic McGrosso, David J Gonzalez, Lars Bode, Hiutung Chu.

The early microbial colonization of the gastrointestinal tract can lead to long-term impacts in development and overall human health. Keystone species, including Bacteroides spp ., play a crucial role in maintaining the structure, diversity, and function of the intestinal ecosystem. However, the process by which a defined and resilient community is curated and maintained during early life remains inadequately understood. Here, we show that a single sialidase, NanH, in Bacteroides fragilis mediates stable occupancy of the intestinal mucosa and regulates the commensal colonization program during the first weeks of life. This program is triggered by sialylated glycans, including those found in human milk oligosaccharides and intestinal mucus. After examining the dynamics between pioneer gut Bacteroides species in the murine gut, we discovered that NanH enables vertical transmission from dams to pups and promotes B. fragilis dominance during early life. Furthermore, we demonstrate that NanH facilitates commensal resilience and recovery after antibiotic treatment in a defined microbial community. Collectively, our study reveals a co-evolutionary mechanism between the host and the microbiota mediated through host-derived glycans to promote stable intestinal colonization.

DOI: https://doi.org/10.1101/2023.08.08.552477
Front Med (Lausanne). 2023 ;10 1105538

Toll-like receptor 4 and Syk kinase shape dendritic cell-induced immune activation to major house dust mite allergens.

Stefanie Busold, Jaap H Akkerdaas, Esther M Zijlstra-Willems, Kees van der Graaf, Sander W Tas, Esther C de Jong, Ronald van Ree, Teunis B H Geijtenbeek.

  Background: House dust mite (HDM) is a major cause of respiratory allergic diseases. Dendritic cells (DCs) play a central role in orchestrating adaptive allergic immune responses. However, it remains unclear how DCs become activated by HDM. Biochemical functions of the major HDM allergens Der p 1 (cysteine protease) and Der p 2 (MD2-mimick) have been implicated to contribute to DC activation.Methods: We investigated the immune activating potential of HDM extract and its major allergens Der p 1 and Der p 2 using monocyte-derived DCs (moDCs). Maturation and activation markers were monitored by flow cytometry and cytokine production by ELISA. Allergen depletion and proteinase K digestion were used to investigate the involvement of proteins, and in particular of the major allergens. Inhibitors of spleen tyrosine kinase (Syk), Toll-like receptor 4 (TLR4) and of C-type lectin receptors (CLRs) were used to identify the involved receptors. The contribution of endotoxins in moDC activation was assessed by their removal from HDM extract.
Results: HDM extract induced DC maturation and cytokine responses in contrast to the natural purified major allergens Der p 1 and Der p 2. Proteinase K digestion and removal of Der p 1 or Der p 2 did not alter the immune stimulatory capacity of HDM extract. Antibodies against the CLRs Dectin-1, Dectin-2, and DC-SIGN did not affect cytokine responses. In contrast, Syk inhibition partially reduced IL-6, IL-12 and completely blocked IL-10. Blocking TLR4 signaling reduced the HDM-induced IL-10 and IL-12p70 induction, but not IL-6, while endotoxin removal potently abolished the induced cytokine response.
Conclusion: Our data strongly suggest that HDM-induced DC activation is neither dependent on Der p 1 nor Der p 2, but depend on Syk and TLR4 activation, which might suggest a crosstalk between Syk and TLR4 pathways. Our data highlight that endotoxins play a potent role in immune responses targeting HDM.

Keywords:  Der p 1; Der p 2; Syk; TLR4; dendritic cell activation; house dust mite allergy

DOI:  https://doi.org/10.3389/fmed.2023.1105538
Eur J Immunol. 2023 Aug 20. e2350393

Reprogramming dendritic cells through the immunological synapse: A two-way street.

Diego Calzada-Fraile, Francisco Sánchez-Madrid.

  Dendritic cells (DCs) bridge innate and adaptive immunity. Their main function is to present antigens to prime T cells and initiate and shape adaptive responses. Antigen presentation takes place through intimate contacts between the two cells, termed immune synapses (IS). During formation of IS, information travels towards the T cell side to induce and tune its activation; but it also travels in reverse via engagement of membrane receptors and within extracellular vesicles transferred to the DC. Such reverse information transfer and its consequences on DC fate have been largely neglected. Here, we review the events and effects of IS-mediated antigen presentation on DCs. In addition, we discuss novel technological advancements that enable monitoring DCs interactions with T lymphocytes, the main effects of DCs undergoing productive IS (post-synaptic DCs, or psDCs), and how reverse information transfer could be harnessed to modulate immune responses for therapeutic intervention. This article is protected by copyright. All rights reserved.

Keywords:  Dendritic cells ⋅ Immunological synapse ⋅ Antigen presentation ⋅ Intercellular communication ⋅ Postsynaptic dendritic cells

DOI:  https://doi.org/10.1002/eji.202350393
PLoS Pathog. 2023 Aug 21. 19(8): e1011600

Bacteriophages targeting protective commensals impair resistance against Salmonella Typhimurium infection in gnotobiotic mice.

Alexandra von Strempel, Anna S Weiss, Johannes Wittmann, Marta Salvado Silva, Diana Ring, Esther Wortmann, Thomas Clavel, Laurent Debarbieux, Karin Kleigrewe, Bärbel Stecher.

Gut microbial communities protect the host against a variety of major human gastrointestinal pathogens. Bacteriophages (phages) are ubiquitous in nature and frequently ingested via food and drinking water. Moreover, they are an attractive tool for microbiome engineering due to the lack of known serious adverse effects on the host. However, the functional role of phages within the gastrointestinal microbiome remain poorly understood. Here, we investigated the effects of microbiota-directed phages on infection with the human enteric pathogen Salmonella enterica serovar Typhimurium (S. Tm), using a gnotobiotic mouse model (OMM14) for colonization resistance (CR). We show, that phage cocktails targeting Escherichia coli and Enterococcus faecalis acted in a strain-specific manner. They transiently reduced the population density of their respective target before establishing coexistence for up to 9 days. Infection susceptibility to S. Tm was markedly increased at an early time point after challenge with both phage cocktails. Surprisingly, OMM14 mice were also susceptible 7 days after a single phage inoculation, when the targeted bacterial populations were back to pre-phage administration density. Concluding, our work shows that phages that dynamically modulate the density of protective members of the gut microbiota can provide opportunities for invasion of bacterial pathogens, in particular at early time points after phage application. This suggests, that phages targeting protective members of the microbiota may increase the risk for Salmonella infection.

DOI: https://doi.org/10.1371/journal.ppat.1011600
Microb Biotechnol. 2023 Aug 21.

Synthetic microbial consortia for the treatment of Clostridioides difficile infection in mice model.

Jinqiu Liu, Wei Zhu, Duncan James Lessing, Weihua Chu.

Clostridioides difficile infection (CDI) as of recent has become a great concern to the impact on human health due to its high hazardous risk and rate of recurrence. Live bacterial therapeutics is a promising method to treat or prevent CDI. Here, a synthetic microbial consortia (SMC) B10 was constructed using probiotic strains with antibacterial and anti-quorum sensing activities, and the therapeutic effect of SMC B10 against C. difficile infection was evaluated in vitro. Compared to the model group, the treatment of SMC B10 significantly increased the survival rate. The clinical signs of mice were significantly ameliorated, especially the cecum injury, while the secretion of pro-inflammatory associated cytokines such as IL-1α, IL-6, IL-17A and TNF-α was reduced, the expression of TLR4 was inhibited, which alleviated the inflammatory response, and the expression of the tight junction protein Claudin-1 was increased, ultimately promoting the recovery of host health. The treatment of B10 restored gut microbiota dysbiosis and led to a healthy intestinal microbiota structure, significantly improved alpha diversity, suppressing potentially harmful bacteria and restoring other core bacterial species. In conclusion, SMC B10 can effectively treat CDI through modulate gut microbiota and attenuate the inflammatory response.

DOI: https://doi.org/10.1111/1751-7915.14333
mSystems. 2023 Aug 23. e0011523

Bacterial multispecies interaction mechanisms dictate biogeographic arrangement between the oral commensals Corynebacterium matruchotii and Streptococcus mitis.

Eric Almeida, Surendra Puri, Alex Labossiere, Subashini Elangovan, Jiyeon Kim, Matthew Ramsey.

  Polymicrobial biofilms are present in many environments particularly in the human oral cavity where they can prevent or facilitate the onset of disease. While recent advances have provided a clear picture of both the constituents and their biogeographic arrangement, it is still unclear what mechanisms of interaction occur between individual species in close proximity within these communities. In this study, we investigated two mechanisms of interaction between the highly abundant supragingival plaque (SUPP) commensal Corynebacterium matruchotii and Streptococcus mitis which are directly adjacent/attached in vivo. We discovered that C. matruchotii enhanced the fitness of streptococci dependent on its ability to detoxify streptococcal-produced hydrogen peroxide and its ability to oxidize lactate also produced by streptococci. We demonstrate that the fitness of adjacent streptococci was linked to that of C. matruchotii and that these mechanisms support the previously described "corncob" arrangement between these species but that this is favorable only in aerobic conditions. Furthermore, we utilized scanning electrochemical microscopy to quantify lactate production and consumption between individual bacterial cells for the first time, revealing that lactate oxidation provides a fitness benefit to S. mitis not due to pH mitigation. This study describes mechanistic interactions between two highly abundant human commensals that can explain their observed in vivo spatial arrangements and suggest a way by which they may help preserve a healthy oral bacterial community. IMPORTANCE As the microbiome era matures, the need for mechanistic interaction data between species is crucial to understand how stable microbiomes are preserved, especially in healthy conditions where the microbiota could help resist opportunistic or exogenous pathogens. Here we reveal multiple mechanisms of interaction between two commensals that dictate their biogeographic relationship to each other in previously described structures in human supragingival plaque. Using a novel variation for chemical detection, we observed metabolite exchange between individual bacterial cells in real time validating the ability of these organisms to carry out metabolic crossfeeding at distal and temporal scales observed in vivo. These findings reveal one way by which these interactions are both favorable to the interacting commensals and potentially the host.

Keywords:  commensal; microbiome; polymicrobial; single cell

DOI:  https://doi.org/10.1128/msystems.00115-23
BMC Microbiol. 2023 Aug 25. 23(1): 235

Multi-host infection and phylogenetically diverse lineages shape the recombination and gene pool dynamics of Staphylococcus aureus.

Stephanie S R Souza, Joshua T Smith, Spencer A Bruce, Robert Gibson, Isabella W Martin, Cheryl P Andam.

  BACKGROUND: Staphylococcus aureus can infect and adapt to multiple host species. However, our understanding of the genetic and evolutionary drivers of its generalist lifestyle remains inadequate. This is particularly important when considering local populations of S. aureus, where close physical proximity between bacterial lineages and between host species may facilitate frequent and repeated interactions between them. Here, we aim to elucidate the genomic differences between human- and animal-derived S. aureus from 437 isolates sampled from disease cases in the northeast region of the United States.RESULTS: Multi-locus sequence typing revealed the existence of 75 previously recognized sequence types (ST). Our population genomic analyses revealed heterogeneity in the accessory genome content of three dominant S. aureus lineages (ST5, ST8, ST30). Genes related to antimicrobial resistance, virulence, and plasmid types were differentially distributed among isolates according to host (human versus non-human) and among the three major STs. Across the entire population, we identified a total of 1,912 recombination events that occurred in 765 genes. The frequency and impact of homologous recombination were comparable between human- and animal-derived isolates. Low-frequency STs were major donors of recombined DNA, regardless of the identity of their host. The most frequently recombined genes (clfB, aroA, sraP) function in host infection and virulence, which were also frequently shared between the rare lineages.
CONCLUSIONS: Taken together, these results show that frequent but variable patterns of recombination among co-circulating S. aureus lineages, including the low-frequency lineages, that traverse host barriers shape the structure of local gene pool and the reservoir of host-associated genetic variants. Our study provides important insights to the genetic and evolutionary factors that contribute to the ability of S. aureus to colonize and cause disease in multiple host species. Our study highlights the importance of continuous surveillance of S. aureus circulating in different ecological host niches and the need to systematically sample from them. These findings will inform development of effective measures to control S. aureus colonization, infection, and transmission across the One Health continuum.

Keywords:  Accessory genome; Core genome; Host; Population genomics; Recombination; Staphylococcus aureus

DOI:  https://doi.org/10.1186/s12866-023-02985-9
Pathogens. 2023 Aug 19. pii: 1064. [Epub ahead of print]12(8):

Host Soluble Factors Cause Changes in Staphylococcus epidermidis Antibiotic Susceptibility and Biofilm Formation Ability.

Fernando Oliveira, Vânia Gaio, Susana Brás, Sofia Oliveira, Angela França.

  Staphylococcus epidermidis is a major nosocomial pathogen with a remarkable ability to adhere to the surfaces of indwelling medical devices and form biofilms. Unlike other nosocomial pathogens, the interaction of S. epidermidis with host factors has not been the focus of substantial research. This study aimed to assess the alterations in the antibiotic susceptibility and biofilm formation ability of S. epidermidis in the presence of host serum factors. S. epidermidis strain RP62A was cultured in a laboratory culture medium with or without human serum/plasma, and changes in antibiotic susceptibility, biofilm formation, and gene expression were evaluated. The data obtained revealed that exposure to host serum factors increased the susceptibility of S. epidermidis to glycopeptide antibiotics and was also detrimental to biofilm formation. Gene expression analysis revealed downregulation of both dltA and fmtC genes shortly after human serum/plasma exposure. The importance of transferrin-mediated iron sequestration as a host anti-biofilm strategy against S. epidermidis was also emphasized. We have demonstrated that serum factors play a pivotal role as part of the host's anti-infective strategy against S. epidermidis infections, highlighting the importance of incorporating such factors during in vitro studies with this pathogen.

Keywords:  anti-bacterial agents; biofilms; gene expression; plasma; serum; staphylococcal infections

DOI:  https://doi.org/10.3390/pathogens12081064
Front Med (Lausanne). 2023 ;10 1182368

Dysregulated cross-talk between alveolar epithelial cells and stromal cells in idiopathic pulmonary fibrosis reduces epithelial regenerative capacity.

Marissa Wisman, Mehmet Nizamoglu, Jacobien A Noordhoek, Wim Timens, Janette K Burgess, Irene H Heijink.

  In idiopathic pulmonary fibrosis (IPF) constant epithelial micro-injury and aberrant interactions within the stromal micro-environment lead to abnormal alveolar repair and fibrosis. We hypothesized that alveolar epithelial regenerative responses in IPF are impaired due to disturbed crosstalk between epithelial cells and their stromal niche. We established organoid cultures from unfractionated suspensions and isolated EpCAM+ cells from distal lung tissue of patients with and without IPF. We observed significantly more organoids being formed from unfractionated suspensions compared to isolated EpCAM+ cell cultures, indicating the presence of supportive cells in the unfractionated suspensions. Importantly, lower organoid numbers were observed in unfractionated cultures from IPF lungs compared to non-IPF lungs. This difference was not found when comparing organoid formation from isolated EpCAM+ cells alone between IPF and non-IPF groups, suggesting that crosstalk between the supportive population and epithelial cells is impaired in lungs from IPF patients. Additionally, organoids grown from IPF lung-derived cells were larger in size compared to those from non-IPF lungs in both unfractionated and EpCAM+ cultures, indicating an intrinsic abnormality in epithelial progenitors from IPF lungs. Together, our observations suggest that dysregulated crosstalk between alveolar progenitor cells and the stromal niche affects the regenerative capacity, potentially contributing to alveolar impairment in IPF.

Keywords:  alveolar epithelial repair; epithelial mesenchymal cross-talk; epithelial regeneration; idiopathic pulmonary fibrosis; lung organoids

DOI:  https://doi.org/10.3389/fmed.2023.1182368