The impact of hypoxia on bacterial infection

A Clinical Decision Support Tool for the Management of Diabetes-Related Foot Ulcers (DRFUs) Using a Topical Haemoglobin Spray

Diabetes related foot ulcers (DFUs) are complex and costly to manage, with the prevalence of non-healing wounds steadily increasing across the globe. Non-healing wounds can occur when clinicians fail to undertake an appropriate assessment, fail to recognise the importance of systemic or local complications, or provide the optimal treatment. The aetiological causes behind non-healing wounds are multifactorial; however, the purpose of this article is to focus on the role of oxygen in non-healing wounds and to introduce readers to advances in the delivery of topical oxygen therapy (TOT) via a haemoglobin spray. Importantly, this article incorporates a clinical decision support tool (CDST) to help clinicians identify the most appropriate individuals for whom topical haemoglobin may be most beneficial and the most appropriate time for introducing the intervention to improve wound healing outcomes.

Temperature-Triggered Reversible Adhesion Hydrogel with Responsive Drug Release, Mild Photothermal Therapy, and Biofilm Clearance for Skin Infection Healing

Bacterial infection gives rise to a hypoxic, H2O2-abundant, and acidic local microenvironment at the site of inflammation, which prevents the healing of skin tissues. In this work, gelatin and oxidized carboxymethyl cellulose were developed as the framework of hydrogels. Tannic acid and 3-formylphenylboronic acid served as small-molecule anchors. Through the introduction of multiple dynamic cross-linkings, the hydrogel was endowed with various functions. These functions encompassed mechanical compatibility with the skin, reversible adhesion characteristics, and rapid self-healing capabilities. In addition, nanoflower-like MnO2 microparticles loaded with berberine hydrochloride were embedded. MnO2 has the ability not only to kill bacteria through the photothermal effect (PTT) but also to catalyze the decomposition of H2O2 and release oxygen, effectively improving the inflammatory microenvironment. Remarkably, based on the drug/PTT synergistic strategy, the hydrogel exhibited significant antibacterial activity and biofilm removal ability under mild conditions (<50 °C), avoiding thermal damage to healthy tissues. Consequently, the hydrogels demonstrate favorable biocompatibility, significant cell proliferation, migration, angiogenesis, collagen deposition, and tissue regeneration. Therefore, the multifunctional antimicrobial hydrogel is expected to be a skin-friendly medical dressing with enormous potential in the treatment of skin and soft tissue infections.

Effective killing of Mycobacterium abscessus biofilm by nanoemulsion delivery of plant phytochemicals

Mycobacterium is an acid-fast, aerobic, non-motile, and biofilm-forming bacterium. The increasing prevalence of mycobacterial infections makes it necessary to find new methods to combat the resistance of bacteria to conventional antibiotics. Mycobacterium abscessus is an emerging pathogen that is intrinsically drug resistant due to several factors, including an impermeable cell envelope, drug efflux pumps, target-modifying enzymes, and the ability to form thick, robust biofilms. Phytochemicals are promising antimicrobials; however, their poor solubility in water and their inability to penetrate biofilms render them inefficient in killing bacterial biofilms. In this study, we demonstrate the efficacy of polymer-stabilized phytochemical nanoemulsions in killing M. abscessus biofilms. These nanoemulsions improve the solubility and stability of the phytochemicals and enable biofilm penetration and eradication. We show that the phytochemical emulsions effectively eliminated M. abscessus in an in vitro biofilm model and killed non-replicating persister cells in the Wayne hypoxia model. These nanoemulsions were also effective in vivo in a wound infection model. These findings demonstrate the potential of polymer-stabilized phytochemical nanoemulsions as a promising alternative to conventional antibiotics for the treatment of mycobacterial infections.

IMPORTANCE

Mycobacterium abscessus is among the opportunistic bacterial pathogens that cause nontuberculous mycobacterial diseases. The infection caused by M. abscessus is difficult to treat because the bacterium is resistant to many of the currently available antibiotics, limiting chemotherapeutic strategies. Furthermore, it forms biofilms in clinically relevant settings, making the infection difficult to treat. Many phytochemicals have potent antimicrobial activities, but their hydrophobicity limits clinical applications. In this study, we tested a new drug delivery strategy where hydrophobic plant phytochemicals were emulsified with a biodegradable nanosponge. We show that the emulsification makes phytochemicals such as carvacrol and eugenol more effective against M. abscessus biofilms. We further demonstrate that nanoemulsified phytochemicals can kill hypoxia-induced dormant M. abscessus and effectively improve skin wound infection in mice. Our data pave the way to use phytochemical nanosponge as a platform to create synergy by combining other antimycobacterial drugs.

Possible role of autophagy in microbial volatile pollutant-induced starch degradation and expression of hypoxia responsive genes

Autophagy is thought to be critically involved in the regulation of nutrient metabolism and gene expression. Nevertheless, little is known about its role in regulating starch metabolism and hypoxia responsive genes in plants exposed to microbial volatile pollutants. In the present study, we found that exposure of Arabidopsis to Enterobacter aerogene (E. aerogene) volatile pollutants induced autophagy, as indicated by autophagosome formation. The exposure also caused upregulation of autophagy-associated genes, such as ATGs, NBR1, ATI1, and ATG8e-regulating transcription factors. Additionally, exposure to E. aerogenes volatile pollutants induced starch degradation in the roots of Arabidopsis seedlings. Finally, we found that ATG7-deficiency negatively affected the expression of hypoxia-responsive genes (i.e HRE1, HRA1, and ADH1) and starch degradation induced by E. aerogenes volatile pollutants. Overall, our study reveals that microbial volatile pollutants can induce starch degradation and autophagy, which participates in the regulation of some hypoxia-responsive genes and starch metabolism. These findings help to define the role of autophagy in plant nutrient metabolism and regulation of gene expression under microbial volatile pollutant exposure. The insights gained may contribute to agricultural management when living organisms face challenges from microbial volatile pollutants.

Biofilm battle: New transformative tactics to tackle the bacterial biofilm infections

Bacterial biofilm infections are the root cause of persistent infections and the prevalence of resistance to specific or multiple antibiotics. Biofilms have unique features that provide a protective environment for bacteria under various stress conditions and contribute significantly to the pathogenesis of chronic infections. They cover bacterial cells with a self-produced extracellular polymeric matrix, effectively hiding the bacterial cells and their targets. Conventional therapies cannot effectively treat and control bacterial biofilm infections. Therefore, advanced therapeutic means like microneedles, targeted tissue therapy, phage therapy, nanodrug therapy, combination drug therapy, microbial therapy, and immune cell hijacking therapy are needed to tackle the complex issue. These advanced therapies have shown promising results not only in bacterial biofilm infections but also in diseases such as cancer and genetic disorders. Due to their unique features and mechanisms, they significantly contribute to preventing bacterial infections by disrupting biofilm. This article aims to serve as a comprehensive overview of the ongoing battle against biofilms with transformative therapies. This article compiles advancements in new therapies that have demonstrated effective roles in the disruption of bacterial biofilms. We also discuss the current developments and Food and Drug Administration-approved status of these therapies. Additionally, this article summarizes the limitations and future steps needed for these therapies in the field of bacterial biofilm prevention. Thus, these therapies represent the future of preventing bacterial biofilm infections and could be also effective in the reversal of resistance.

Supramolecular discrimination and diagnosis-guided treatment of intracellular bacteria

Pathogenic intracellular bacteria pose a significant threat to global public health due to the barriers presented by host cells hindering the timely detection of hidden bacteria and the effective delivery of therapeutic agents. To address these challenges, we propose a tandem diagnosis-guided treatment paradigm. A supramolecular sensor array is developed for simple, rapid, accurate, and high-throughput identification of intracellular bacteria. This diagnostic approach executes the significant guiding missions of screening a customized host-guest drug delivery system by disclosing the rationale behind the discrimination. We design eight azocalix[4]arenes with differential active targeting, cellular internalization, and hypoxia responsiveness to penetrate cells and interact with bacteria. Loaded with fluorescent indicators, these azocalix[4]arenes form a sensor array capable of discriminating eight intracellular bacterial species without cell lysis or separation. By fingerprinting specimens collected from bacteria-infected mice, the facilitated accurate diagnosis offers valuable guidance for selecting appropriate antibiotics. Moreover, mannose-modified azocalix[4]arene (ManAC4A) is screened as a drug carrier efficiently taken up by macrophages. Doxycycline loaded with ManAC4A exhibits improved efficacy against methicillin-resistant Staphylococcus aureus-infected peritonitis. This study introduces an emerging paradigm to intracellular bacterial diagnosis and treatment, offering broad potential in combating bacterial infectious diseases.

Implant-Derived S. aureus Isolates Drive Strain-Specific Invasion Dynamics and Bioenergetic Alterations in Osteoblasts

Background: Implants are integral to modern orthopedic surgery. The outcomes are good, but infections remain a serious issue. Staphylococcus aureus (S. aureus), along with Staphylococcus epidermidis, are predominant pathogens responsible for implant-associated infections, as conventional antibiotic treatments often fail due to biofilm formation or the pathogens' ability to invade cells and to persist intracellularly. Objectives: This study therefore focused on interactions of S. aureus isolates from infected implants with MG63 and SaOS2 osteoblasts by investigating the adhesion, invasion, and the impact on the bioenergetics of osteoblasts. Methods and Results: We found that the ability of S. aureus to adhere to osteoblasts depends on the isolate and was not associated with a single gene or expression pattern of characteristic adhesion proteins, and further, was not correlated with invasion. However, analysis of invasion capabilities identified better invasion conditions for S. aureus isolates with the SaOS2 osteoblastic cells. Interestingly, metabolic activity of osteoblasts remained unaffected by S. aureus infection, indicating cell survival. In contrast, respiration assays revealed an altered mitochondrial bioenergetic turnover in infected cells. While basal as well as maximal respiration in MG63 osteoblasts were not influenced statistically by S. aureus infections, we found increased non-mitochondrial respiration and enhanced glycolytic activity in the osteoblasts, which was again, more pronounced in the SaOS2 osteoblastic cells. Conclusions: Our findings highlight the complexity of S. aureus-host interactions, where both the pathogen and the host cell contribute to intracellular persistence and survival, representing a major factor for therapeutic failures.

Regulation of PHD2 by HIF-1α in Erythroid Cells: Insights into Erythropoiesis Under Hypoxia

The hypoxia-inducible factor (HIF) pathway has been demonstrated to play a pivotal role in the process of high-altitude adaptation. PHD2, a key regulator of the HIF pathway, has been found to be associated with erythropoiesis. However, the relationship between changes in Phd2 abundance and erythroid differentiation under hypoxic conditions remains to be elucidated. A hemin-induced K562 erythroid differentiation model was used to explore the effects of PHD2 knockdown under hypoxia. Erythroid differentiation was assessed by flow cytometry and immunofluorescence. HIF-1α's regulation of PHD2 was examined using luciferase assays and ChIP-seq. CRISPR/Cas9 was applied to knock out EGLN1 and HIF1A, and a fluorescent reporter system was developed to track PHD2 expression. PHD2 knockdown enhanced erythroid differentiation, evident by increased CD71 and CD235a expression. Reporter assays and ChIP-seq identified an HIF-1α binding site in the EGLN1 5' UTR, confirming HIF-1α as a regulator of PHD2 expression. The fluorescent reporter system provided real-time monitoring of endogenous PHD2 expression, showing that HIF-1α significantly modulates PHD2 levels under hypoxic conditions. PHD2 influences erythropoiesis under hypoxia, with HIF-1α regulating its expression. This feedback loop between HIF-1α and PHD2 sheds light on mechanisms driving erythroid differentiation under low-oxygen conditions.

Harnessing hypoxia: bacterial adaptation and chronic infection in cystic fibrosis

The exquisite ability of bacteria to adapt to their environment is essential for their capacity to colonize hostile niches. In the cystic fibrosis (CF) lung, hypoxia is among several environmental stresses that opportunistic pathogens must overcome to persist and chronically colonize. Although the role of hypoxia in the host has been widely reviewed, the impact of hypoxia on bacterial pathogens has not yet been studied extensively. This review considers the bacterial oxygen-sensing mechanisms in three species that effectively colonize the lungs of people with CF, namely Pseudomonas aeruginosa, Burkholderia cepacia complex, and Mycobacterium abscessus and draws parallels between their three proposed oxygen-sensing two-component systems: BfiSR, FixLJ, and DosRS, respectively. Moreover, each species expresses regulons that respond to hypoxia: Anr, Lxa, and DosR, and encode multiple proteins that share similar homologies and function. Many adaptations that these pathogens undergo during chronic infection, including antibiotic resistance, protease expression, or changes in motility, have parallels in the responses of the respective species to hypoxia. It is likely that exposure to hypoxia in their environmental habitats predispose these pathogens to colonization of hypoxic niches, arming them with mechanisms than enable their evasion of the immune system and establish chronic infections. Overcoming hypoxia presents a new target for therapeutic options against chronic lung infections.

Intratumoral Microbiota: Metabolic Influences and Biomarker Potential in Gastrointestinal Cancer

Gastrointestinal (GI) cancers impose a substantial global health burden, highlighting the necessity for deeper understanding of their intricate pathogenesis and treatment strategies. This review explores the interplay between intratumoral microbiota, tumor metabolism, and major types of GI cancers (including esophageal, gastric, liver, pancreatic, and colorectal cancers), summarizing recent studies and elucidating their clinical implications and future directions. Recent research revealed altered microbial signatures within GI tumors, impacting tumor progression, immune responses, and treatment outcomes. Dysbiosis-induced alterations in tumor metabolism, including glycolysis, fatty acid metabolism, and amino acid metabolism, play critical roles in cancer progression and therapeutic resistance. The integration of molecular mechanisms and potential biomarkers into this understanding further enhances the prognostic significance of intratumoral microbiota composition and therapeutic opportunities targeting microbiota-mediated tumor metabolism. Despite advancements, challenges remain in understanding the dynamic interactions within the tumor microenvironment (TME). Future research directions, including advanced omics technologies and prospective clinical studies, offer promising avenues for precision oncology and personalized treatment interventions in GI cancer. Overall, integrating microbiota-based approaches and molecular biomarkers into GI cancer management holds promise for improving patient outcomes and survival.

Photodynamic therapy alone or in combination to counteract bacterial infections

INTRODUCTION

Antibacterial photodynamic therapy presents a promising alternative to antibiotics, with potential against multidrug-resistant bacteria, offering broad-spectrum action, reduced resistance risk, and improved tissue selectivity.

AREAS COVERED

This manuscript reviews patent literature in the field of antibacterial photodynamic therapy through the period of 2019-2023. All data are from the US and European patent databases and SciFinder.

EXPERT OPINION

Antibacterial photodynamic therapy (PDT) is an appealing approach for treating bacterial infections, especially biofilm-related ones, by releasing reactive oxygen species (ROS) upon light activation. Its success is driven by a growing variety of photosensitizers (PSs) with tailored properties, like water solubility, controllable surface charge, and ROS generation efficiency. Among them, Aggregation Induced Emission (AIE)-type PSs are promising, demonstrating enhanced efficacy when aggregated in biological environments. However, the penetration of pristine PSs into bacterial biofilms within deep tissues or complex anatomical regions is limited, reducing their antibacterial effectiveness. To address this, nanotechnology has been integrated into antibacterial PDT to synthesize various nano-PSs. This adaptability allows seamless integration with other antimicrobial treatments, offering a comprehensive approach to combat localized infections, especially in dentistry and dermatology. By combining PSs with complementary therapies, antibacterial PDT offers a multifaceted strategy for effective microbial control and management.

Live Microscopy of Multicellular Spheroids with the Multimodal Near-Infrared Nanoparticles Reveals Differences in Oxygenation Gradients

Assessment of hypoxia, nutrients, metabolite gradients, and other hallmarks of the tumor microenvironment within 3D multicellular spheroid and organoid models represents a challenging analytical task. Here, we report red/near-infrared (NIR) emitting cell staining with O2-sensitive nanoparticles, which enable measurements of spheroid oxygenation on a conventional fluorescence microscope. Nanosensor probes, termed "MMIR" (multimodal infrared), incorporate an NIR O2-sensitive metalloporphyrin (PtTPTBPF) and deep red aza-BODIPY reference dyes within a biocompatible polymer shell, allowing for oxygen gradient quantification via fluorescence ratio and phosphorescence lifetime readouts. We optimized staining techniques and evaluated the nanosensor probe characteristics and cytotoxicity. Subsequently, we applied nanosensors to the live spheroid models based on HCT116, DPSCs, and SKOV3 cells, at rest, and treated with drugs affecting cell respiration. We found that the growth medium viscosity, spheroid size, and formation method influenced spheroid oxygenation. Some spheroids produced from HCT116 and dental pulp stem cells exhibited "inverted" oxygenation gradients, with higher core oxygen levels than the periphery. This contrasted with the frequently encountered "normal" gradient of hypoxia toward the core caused by diffusion. Further microscopy analysis of spheroids with an "inverted" gradient demonstrated metabolic stratification of cells within spheroids: thus, autofluorescence FLIM of NAD(P)H indicated the formation of a glycolytic core and localization of OxPhos-active cells at the periphery. Collectively, we demonstrate a strong potential of NIR-emitting ratiometric nanosensors for advanced microscopy studies targeting live and quantitative real-time monitoring of cell metabolism and hypoxia in complex 3D tissue models.

A pan-cancer analysis of the microbiome in metastatic cancer

Microbial communities are resident to multiple niches of the human body and are important modulators of the host immune system and responses to anticancer therapies. Recent studies have shown that complex microbial communities are present within primary tumors. To investigate the presence and relevance of the microbiome in metastases, we integrated mapping and assembly-based metagenomics, genomics, transcriptomics, and clinical data of 4,160 metastatic tumor biopsies. We identified organ-specific tropisms of microbes, enrichments of anaerobic bacteria in hypoxic tumors, associations between microbial diversity and tumor-infiltrating neutrophils, and the association of Fusobacterium with resistance to immune checkpoint blockade (ICB) in lung cancer. Furthermore, longitudinal tumor sampling revealed temporal evolution of the microbial communities and identified bacteria depleted upon ICB. Together, we generated a pan-cancer resource of the metastatic tumor microbiome that may contribute to advancing treatment strategies.

Contemporary national outcomes of hyperbaric oxygen therapy in necrotizing soft tissue infections

BACKGROUND

The role of hyperbaric oxygen therapy (HBOT) in necrotizing soft tissue infections (NSTI) is mainly based on small retrospective studies. A previous study using the 1998-2009 National Inpatient Sample (NIS) found HBOT to be associated with decreased mortality in NSTI. Given the argument of advancements in critical care, we aimed to investigate the continued role of HBOT in NSTI.

METHODS

The 2012-2020 National Inpatient Sample (NIS) was queried for NSTI admissions who received surgery. 60,481 patients between 2012-2020 were included, 600 (<1%) underwent HBOT. Primary outcome was in-hospital mortality. Secondary outcomes included amputation, hospital length of stay, and costs. A multivariate model was constructed to account for baseline differences in groups.

RESULTS

Age, gender, and comorbidities were similar between the two groups. On bivariate comparison, the HBOT group had lower mortality rate (<2% vs 5.9%, p<0.001) and lower amputation rate (11.8% vs 18.3%, p<0.001) however, longer lengths of stay (16.9 days vs 14.6 days, p<0.001) and higher costs ($54,000 vs $46,000, p<0.001). After multivariate analysis, HBOT was associated with decreased mortality (Adjusted Odds Ratio (AOR) 0.22, 95% CI 0.09-0.53, P<0.001) and lower risk of amputation (AOR 0.73, 95% CI 0.55-0.96, P = 0.03). HBO was associated with longer stays by 1.6 days (95% CI 0.4-2.7 days) and increased costs by $7,800 (95% CI $2,200-$13,300), they also had significantly lower risks of non-home discharges (AOR 0.79, 95%CI 0.65-0.96).

CONCLUSIONS

After correction for differences, HBOT was associated with decreased mortality, amputations, and non-home discharges in NSTI with the tradeoff of increase to costs and length of stay.

Current understandings of colibactin regulation

The biosynthetic machinery for the production of colibactin is encoded by 19 genes (clbA - S) within the pks pathogenicity island harboured by many E. coli of the B2-phylogroup. Colibactin is a potent genotoxic metabolite which causes DNA-damage and which has potential roles in microbial competition and fitness of pks+ bacteria. Colibactin has also been strongly implicated in the development of colorectal cancer. Given the genotoxicity of colibactin and the metabolic cost of its synthesis, the regulatory system governing the clb cluster is accordingly highly complex, and many of the mechanisms remain to be elucidated. In this review we summarise the current understanding of regulation of colibactin biosynthesis by internal molecular components and how these factors are modulated by signals from the external environment.

In-situ-sprayed therapeutic hydrogel for oxygen-actuated Janus regulation of postsurgical tumor recurrence/metastasis and wound healing

Surgery is the mainstay of treatment modality for malignant melanoma. However, the deteriorative hypoxic microenvironment after surgery is recognized as a stemming cause for tumor recurrence/metastasis and delayed wound healing. Here we design and construct a sprayable therapeutic hydrogel (HIL@Z/P/H) encapsulating tumor-targeted nanodrug and photosynthetic cyanobacteria (PCC 7942) to prevent tumor recurrence/metastasis while promote wound healing. In a postsurgical B16F10 melanoma model in female mice, the nanodrug can disrupt cellular redox homeostasis via the photodynamic therapy-induced cascade reactions within tumor cells. Besides, the photosynthetically generated O2 by PCC 7942 can not only potentiate the oxidative stress-triggered cell death to prevent local recurrence of residual tumor cells, but also block the signaling pathway of hypoxia-inducible factor 1α to inhibit their distant metastasis. Furthermore, the long-lasting O2 supply and PCC 7942-secreted extracellular vesicles can jointly promote angiogenesis and accelerate the wound healing process. Taken together, the developed HIL@Z/P/H capable of preventing tumor recurrence/metastasis while promoting wound healing shows great application potential for postsurgical cancer therapy.

Association of Chlamydia trachomatis burden with the vaginal microbiota, bacterial vaginosis, and metronidazole treatment

Bacterial vaginosis (BV), a dysbiosis of the vaginal microbiota, is a common coinfection with Chlamydia trachomatis (Ct), and BV-associated bacteria (BVAB) and their products have been implicated in aiding Ct evade natural immunity. Here, we determined if a non-optimal vaginal microbiota was associated with a higher genital Ct burden and if metronidazole, a standard treatment for BV, would reduce Ct burden or aid in natural clearance of Ct infection. Cervicovaginal samples were collected from women at enrollment and, if testing positive for Ct infection, at a follow-up visit approximately one week later. Cervical Ct burden was assessed by inclusion forming units (IFU) and Ct genome copy number (GCN), and 16S rRNA gene sequencing was used to determine the composition of the vaginal microbiota. We observed a six-log spectrum of IFU and an eight-log spectrum of GCN in our study participants at their enrollment visit, but BV, as indicated by Amsel's criteria, Nugent scoring, or VALENCIA community state typing, did not predict infectious and total Ct burden, although IFU : GCN increased with Amsel and Nugent scores and in BV-like community state types. Ct burden was, however, associated with the abundance of bacterial species in the vaginal microbiota, negatively with Lactobacillus crispatus and positively with Prevotella bivia. Women diagnosed with BV were treated with metronidazole, and Ct burden was significantly reduced in those who resolved BV with treatment. A subset of women naturally cleared Ct infection in the interim, typified by low Ct burden at enrollment and resolution of BV. Abundance of many BVAB decreased, and Lactobacillus increased, in response to metronidazole treatment, but no changes in abundances of specific vaginal bacteria were unique to women who spontaneously cleared Ct infection.

Candidate signatures of positive selection for environmental adaptation in indigenous African cattle: A review

Environmental adaptation traits of indigenous African cattle are increasingly being investigated to respond to the need for sustainable livestock production in the context of unpredictable climatic changes. Several studies have highlighted genomic regions under positive selection probably associated with adaptation to environmental challenges (e.g. heat stress, trypanosomiasis, tick and tick-borne diseases). However, little attention has focused on pinpointing the candidate causative variant(s) controlling the traits. This review compiled information from 22 studies on signatures of positive selection in indigenous African cattle breeds to identify regions under positive selection. We highlight some key candidate genome regions and genes of relevance to the challenges of living in extreme environments (high temperature, high altitude, high infectious disease prevalence). They include candidate genes involved in biological pathways relating to innate and adaptive immunity (e.g. BoLAs, SPAG11, IL1RL2 and GFI1B), heat stress (e.g. HSPs, SOD1 and PRLH) and hypoxia responses (e.g. BDNF and INPP4A). Notably, the highest numbers of candidate regions are found on BTA3, BTA5 and BTA7. They overlap with genes playing roles in several biological functions and pathways. These include but are not limited to growth and feed intake, cell stability, protein stability and sweat gland development. This review may further guide targeted genome studies aiming to assess the importance of candidate causative mutations, within regulatory and protein-coding genome regions, to further understand the biological mechanisms underlying African cattle's unique adaption.

Anaerobic growth and drug susceptibility of versatile fungal pathogen Scedosporium apiospermum

Although severe cases of invasive mycoses of different hypoxic and anoxic body parts have been reported, growth and drug susceptibility of fungal pathogens under anaerobic conditions remains understudied. The current study evaluated anaerobic growth potential and drug susceptibility of environmental Scedosporium apiospermum isolates under aerobic and anaerobic conditions. All tested strains showed equivalent growth and higher sensitivity to tested antifungal drugs under anaerobic conditions with lower minimum inhibitory concentration (MIC) as compared to aerobic conditions. Antifungal azoles were effective against isolates under both aerobic and anaerobic conditions. Most strains were resistant to antifungal echinocandins and polyenes under aerobic conditions but exhibited sensitivity under anaerobic conditions. This study provides evidence that resistance of S. apiospermum to antifungal drugs varies with oxygen concentration and availability and suggests re-evaluating clinical breakpoints for antifungal compounds to treat invasive fungal infections more effectively.

Genetically predicted obstructive sleep apnea is causally associated with an increased risk for periodontitis

BACKGROUND

Although obstructive sleep apnea (OSA) and periodontitis are associated, whether this association is causative is uncertain.

METHODS

We conducted a bidirectional Mendelian randomization (MR) analysis using data from publically accessible genome-wide association studies. The single-nucleotide polymorphisms (SNPs) for OSA were derived from 16,761 cases and 201,194 controls. The pooled data of periodontitis association involved up to 17,353 individuals. Disease-associated single-nucleotide polymorphisms were selected as an instrumental variable at the genome-wide significance level (p < 5.0 × 10- 6). Subsequently, the causal effects were estimated using three different methods: inverse variance weighting (IVW), MR-Egger, and weighted median. Then, these causal estimates were expressed as dominance ratios [odds ratio (OR)].

RESULTS

The MR analysis revealed that genetically determined OSA promotes the development of periodontitis [ IVW OR = 1.117, 95% confidence interval (CI) = 1.001-1.246, p = 0.048). Furthermore, no causal effect of genetically predicted periodontitis on OSA was noted in the reverse MR analysis (IVW OR = 1, 95% CI: 0.95-1.06, p = 0.87). The trend in results from the MR-Egger regression and weighted median (WM) was consistent with that in results from the IVW method. The robustness of the results was confirmed by the sensitivity analysis.

CONCLUSIONS

In summary, the results of our MR investigation suggest an association between OSA and periodontitis, proposing that early screening and treatment of OSA is beneficial for the prevention and prognosis of periodontitis.

Prevalence, Microbial Etiology and Risk Factors Associated With Healthcare Associated Infections Among End Stage Renal Disease Patients on Renal Replacement Therapy

End stage renal disease (ESRD) patients on renal replacement therapy (RRT) have an increased risk of morbidity and mortality due to healthcare associated infections (HCAIs). The aim of this study is to determine the prevalence, microbial etiology, and risk factors associated with HCAIs among ESRD patients on RRT. A multicenter, retrospective study was conducted from June to December 2019. ESRD patients with minimum of 6 months on RRT were included, while pregnant patients and patients <18 years were excluded. To reduce the risk of selection bias, all patients were randomly selected using a simple random sampling technique. The prevalence showing the proportion of patients that acquired HCAI since the initiation of dialysis until 2019 was calculated using the European patients' academy (EUPATI) formula. Risk factors were assessed using univariate and multivariate regression analysis. The prevalence of HCAI among ESRD patients was 174/400 (43.5%). Catheter related bloodstream infection (CRBSI) was the most common infection [64(36.8%)], followed by peritonitis [45(25.8%)] and pneumonia [37(21.2%)]. Out of 382 total pathogens identified, 204 (53.4%) were Gram positive and 162 (42.4%) were Gram negative. Both methicillin sensitive staphylococcus aureus (MSSA) and methicillin resistant staphylococcus aureus (MRSA) showed statistically significant associations (p<0.05) with CRBSI. Use of multiple accesses, increased blood sugar levels, low serum sodium levels and higher CRP concentration increased the occurrence of HCAIs. The burden of HCAIs among the patients undergoing RRT is high. Preventive strategies and optimum empirical therapy of antibiotics should be used to reduce the risk of these infections among ESRD patients.

Metformin Reduces Bone Resorption in Apical Periodontitis Through Regulation of Osteoblast and Osteoclast Differentiation

INTRODUCTION

We have previously demonstrated that auxiliary metformin therapy promotes healing of apical periodontitis. Here we aimed to investigate the effects of metformin on osteoblast differentiation and osteoclast formation in cultured cells and rat apical periodontitis.

METHODS

Murine pre-osteoblasts MC3T3-E1 and macrophages RAW264.7 were cultured under hypoxia (2% oxygen) or normoxia (21% oxygen) and stimulated with receptor activator of nuclear factor-κB ligand (RANKL) when indicated. Metformin was added to the cultures to evaluate its anti-hypoxic effects. Expressions of osteoblast differentiation regulator runt-related transcription factor 2 (RUNX2), RANKL, and osteoclast marker tartrate-resistant acid phosphatase (TRAP) were assessed by Western blot. Apical periodontitis was induced in mandibular first molars of 10 Sprague-Dawley rats. Root canal therapy with or without metformin supplement was performed. Periapical bone resorption was measured by micro-computed tomography. Immunohistochemistry was used to examine RUNX2, RANKL, and TRAP expressions.

RESULTS

Hypoxia suppressed RUNX2 expression and enhanced RANKL synthesis in pre-osteoblasts. TRAP production increased in macrophages after hypoxia and/or RANKL stimulation. Metformin reversed hypoxia-induced RUNX2 suppression and RANKL synthesis in pre-osteoblasts. Metformin also inhibited hypoxia and RANKL-enhanced TRAP synthesis in macrophages. Intracanal metformin diminished bone loss in rat apical periodontitis. Comparing with vehicle control, cells lining bone surfaces in metformin-treated lesions had significantly stronger expression of RUNX2 and decreased synthesis of RANKL and TRAP.

CONCLUSIONS

Alleviation of bone resorption by intracanal metformin was associated with enhanced osteoblast differentiation and diminished osteoclast formation in rat apical periodontitis. Our results endorsed the role of metformin as an effective medicament for inflammatory bone diseases.

Metabolic rewiring tunes dermal macrophages in staphylococcal skin infection

The skin needs to balance tolerance of colonizing microflora with rapid detection of potential pathogens. Flexible response mechanisms would seem most suitable to accommodate the dynamic challenges of effective antimicrobial defense and restoration of tissue homeostasis. Here, we dissected macrophage-intrinsic mechanisms and microenvironmental cues that tune macrophage signaling in localized skin infection with the colonizing and opportunistic pathogen Staphylococcus aureus. Early in skin infection, the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) produced by γδ T cells and hypoxic conditions within the dermal microenvironment diverted macrophages away from a homeostatic M-CSF- and hypoxia-inducible factor 1α (HIF-1α)-dependent program. This allowed macrophages to be metabolically rewired for maximal inflammatory activity, which requires expression of Irg1 and generation of itaconate, but not HIF-1α. This multifactorial macrophage rewiring program was required for both the timely clearance of bacteria and for the provision of local immune memory. These findings indicate that immunometabolic conditioning allows dermal macrophages to cycle between antimicrobial activity and protection against secondary infections.

Molecular correlates of vaccine-induced protection against typhoid fever

BACKGROUNDTyphoid fever is caused by the Gram-negative bacterium Salmonella enterica serovar Typhi and poses a substantial public health burden worldwide. Vaccines have been developed based on the surface Vi-capsular polysaccharide of S. Typhi; these include a plain-polysaccharide-based vaccine, ViPS, and a glycoconjugate vaccine, ViTT. To understand immune responses to these vaccines and their vaccine-induced immunological protection, molecular signatures were analyzed using bioinformatic approaches.METHODSBulk RNA-Seq data were generated from blood samples obtained from adult human volunteers enrolled in a vaccine trial, who were then challenged with S. Typhi in a controlled human infection model (CHIM). These data were used to conduct differential gene expression analyses, gene set and modular analyses, B cell repertoire analyses, and time-course analyses at various post-vaccination and post-challenge time points between participants receiving ViTT, ViPS, or a control meningococcal vaccine.RESULTSTranscriptomic responses revealed strong differential molecular signatures between the 2 typhoid vaccines, mostly driven by the upregulation in humoral immune signatures, including selective usage of immunoglobulin heavy chain variable region (IGHV) genes and more polarized clonal expansions. We describe several molecular correlates of protection against S. Typhi infection, including clusters of B cell receptor (BCR) clonotypes associated with protection, with known binders of Vi-polysaccharide among these.CONCLUSIONThe study reports a series of contemporary analyses that reveal the transcriptomic signatures after vaccination and infectious challenge, while identifying molecular correlates of protection that may inform future vaccine design and assessment.TRIAL REGISTRATIONClinicalTrials.gov NCT02324751.

Proteomic analysis to identification of hypoxia related markers in spinal tuberculosis: a study based on weighted gene co-expression network analysis and machine learning

OBJECTIVE

This article aims at exploring the role of hypoxia-related genes and immune cells in spinal tuberculosis and tuberculosis involving other organs.

METHODS

In this study, label-free quantitative proteomics analysis was performed on the intervertebral discs (fibrous cartilaginous tissues) obtained from five spinal tuberculosis (TB) patients. Key proteins associated with hypoxia were identified using molecular complex detection (MCODE), weighted gene co-expression network analysis(WGCNA), least absolute shrinkage and selection operator (LASSO), and support vector machine recursive feature Elimination (SVM-REF) methods, and their diagnostic and predictive values were assessed. Immune cell correlation analysis was then performed using the Single Sample Gene Set Enrichment Analysis (ssGSEA) method. In addition, a pharmaco-transcriptomic analysis was also performed to identify targets for treatment.

RESULTS

The three genes, namely proteasome 20 S subunit beta 9 (PSMB9), signal transducer and activator of transcription 1 (STAT1), and transporter 1 (TAP1), were identified in the present study. The expression of these genes was found to be particularly high in patients with spinal TB and other extrapulmonary TB, as well as in TB and multidrug-resistant TB (p-value < 0.05). They revealed high diagnostic and predictive values and were closely related to the expression of multiple immune cells (p-value < 0.05). It was inferred that the expression of PSMB9, STAT 1, and TAP1 could be regulated by different medicinal chemicals.

CONCLUSION

PSMB9, STAT1, and TAP1, might play a key role in the pathogenesis of TB, including spinal TB, and the protein product of the genes can be served as diagnostic markers and potential therapeutic target for TB.

Sorangicin A Is Active against Chlamydia in Cell Culture, Explanted Fallopian Tubes, and Topical In Vivo Treatment

Current treatment of Chlamydia trachomatis using doxycycline and azithromycin introduces detrimental side effects on the host's microbiota. As a potential alternative treatment, the myxobacterial natural product sorangicin A (SorA) blocks the bacterial RNA polymerase. In this study we analyzed the effectiveness of SorA against C. trachomatis in cell culture, and explanted fallopian tubes and systemic and local treatment in mice, providing also pharmacokinetic data on SorA. Potential side effects of SorA on the vaginal and gut microbiome were assessed in mice and against human-derived Lactobacillus species. SorA showed minimal inhibitory concentrations of 80 ng/mL (normoxia) to 120 ng/mL (hypoxia) against C. trachomatis in vitro and was eradicating C. trachomatis at a concentration of 1 µg/mL from fallopian tubes. In vivo, SorA reduced chlamydial shedding by more than 100-fold within the first days of infection by topical application corresponding with vaginal detection of SorA only upon topical treatment, but not after systemic application. SorA changed gut microbial composition during intraperitoneal application only and did neither alter the vaginal microbiota in mice nor affect growth of human-derived lactobacilli. Additional dose escalations and/or pharmaceutical modifications will be needed to optimize application of SorA and to reach sufficient anti-chlamydial activity in vivo.

Under-oil open microfluidic systems for rapid phenotypic antimicrobial susceptibility testing

Antimicrobial susceptibility testing (AST) remains the cornerstone of effective antimicrobial selection and optimization in patients. Despite recent advances in rapid pathogen identification and resistance marker detection with molecular diagnostics (e.g., qPCR, MALDI-TOF MS), phenotypic (i.e., microbial culture-based) AST methods - the gold standard in hospitals/clinics - remain relatively unchanged over the last few decades. Microfluidics-based phenotypic AST has been growing fast in recent years, aiming for rapid (i.e., turnaround time <8 h), high-throughput, and automated species identification, resistance detection, and antibiotics screening. In this pilot study, we describe the application of a multi-liquid-phase open microfluidic system, named under-oil open microfluidic systems (UOMS), to achieve a rapid phenotypic AST. UOMS provides an open microfluidics-based solution for rapid phenotypic AST (UOMS-AST) by implementing and recording a pathogen's antimicrobial activity in micro-volume testing units under an oil overlay. UOMS-AST allows free physical access (e.g., by standard pipetting) to the system and label-free, single-cell resolution optical access. UOMS-AST can accurately and rapidly determine antimicrobial activities [including susceptibility/resistance breakpoint and minimum inhibitory concentration (MIC)] from nominal sample/bacterial cells in a system aligned with clinical laboratory standards where open systems and optical microscopy are predominantly adopted. Further, we combine UOMS-AST with a cloud lab data analytic technique for real-time image analysis and report generation to provide a rapid (<4 h) sample-to-report turnaround time, shedding light on its utility as a versatile (e.g., low-resource setting and manual laboratory operation, or high-throughput automated system) phenotypic AST platform for hospital/clinic use.

Molecular and Functional Characteristics of Airway Epithelium under Chronic Hypoxia

Localized and chronic hypoxia of airway mucosa is a common feature of progressive respiratory diseases, including cystic fibrosis (CF). However, the impact of prolonged hypoxia on airway stem cell function and differentiated epithelium is not well elucidated. Acute hypoxia alters the transcription and translation of many genes, including the CF transmembrane conductance regulator (CFTR). CFTR-targeted therapies (modulators) have not been investigated in vitro under chronic hypoxic conditions found in CF airways in vivo. Nasal epithelial cells (hNECs) derived from eight CF and three non-CF participants were expanded and differentiated at the air-liquid interface (26-30 days) at ambient and 2% oxygen tension (hypoxia). Morphology, global proteomics (LC-MS/MS) and function (barrier integrity, cilia motility and ion transport) of basal stem cells and differentiated cultures were assessed. hNECs expanded at chronic hypoxia, demonstrating epithelial cobblestone morphology and a similar proliferation rate to hNECs expanded at normoxia. Hypoxia-inducible proteins and pathways in stem cells and differentiated cultures were identified. Despite the stem cells' plasticity and adaptation to chronic hypoxia, the differentiated epithelium was significantly thinner with reduced barrier integrity. Stem cell lineage commitment shifted to a more secretory epithelial phenotype. Motile cilia abundance, length, beat frequency and coordination were significantly negatively modulated. Chronic hypoxia reduces the activity of epithelial sodium and CFTR ion channels. CFTR modulator drug response was diminished. Our findings shed light on the molecular pathophysiology of hypoxia and its implications in CF. Targeting hypoxia can be a strategy to augment mucosal function and may provide a means to enhance the efficacy of CFTR modulators.

Ultrastructural Evidence of Mitochondrial Dysfunction in Osteomyelitis Patients

Osteomyelitis is a difficult-to-treat disease with high chronification rates. First studies suggest increases in mitochondrial fission and mitochondrial dysfunction as possible contributors to the accumulation of intracellular reactive oxygen species and thereby to the cell death of infected bone cells. The aim of the present study is to analyze the ultrastructural impact of bacterial infection on osteocytic and osteoblastic mitochondria. Human infected bone tissue samples were visualized via light microscopy and transmission electron microscopy. Osteoblasts, osteocytes and their mitochondria were analyzed histomorphometrically and compared with the control group of noninfectious human bone tissue samples. The results depicted swollen hydropic mitochondria including depleted cristae and a decrease in matrix density in the infected samples. Furthermore, perinuclear clustering of mitochondria could also be observed regularly. Additionally, increases in relative mitochondrial area and number were found as a correlate for increased mitochondrial fission. In conclusion, mitochondrial morphology is altered during osteomyelitis in a comparable way to mitochondria from hypoxic tissues. This gives new perspectives on the treatment strategies since the manipulation of mitochondrial dynamics may improve bone cell survival as a potential new target for the therapy of osteomyelitis.

Bovine blood derived macrophages are unable to control Coxiella burnetii replication under hypoxic conditions

Background

Coxiella burnetii is a zoonotic pathogen, infecting humans, livestock, pets, birds and ticks. Domestic ruminants such as cattle, sheep, and goats are the main reservoir and major cause of human infection. Infected ruminants are usually asymptomatic, while in humans infection can cause significant disease. Human and bovine macrophages differ in their permissiveness for C. burnetii strains from different host species and of various genotypes and their subsequent host cell response, but the underlying mechanism(s) at the cellular level are unknown.

Methods

C. burnetii infected primary human and bovine macrophages under normoxic and hypoxic conditions were analyzed for (i) bacterial replication by CFU counts and immunofluorescence; (ii) immune regulators by westernblot and qRT-PCR; cytokines by ELISA; and metabolites by gas chromatography-mass spectrometry (GC-MS).

Results

Here, we confirmed that peripheral blood-derived human macrophages prevent C. burnetii replication under oxygen-limiting conditions. In contrast, oxygen content had no influence on C. burnetii replication in bovine peripheral blood-derived macrophages. In hypoxic infected bovine macrophages, STAT3 is activated, even though HIF1α is stabilized, which otherwise prevents STAT3 activation in human macrophages. In addition, the TNFα mRNA level is higher in hypoxic than normoxic human macrophages, which correlates with increased secretion of TNFα and control of C. burnetii replication. In contrast, oxygen limitation does not impact TNFα mRNA levels in C. burnetii-infected bovine macrophages and secretion of TNFα is blocked. As TNFα is also involved in the control of C. burnetii replication in bovine macrophages, this cytokine is important for cell autonomous control and its absence is partially responsible for the ability of C. burnetii to replicate in hypoxic bovine macrophages. Further unveiling the molecular basis of macrophage-mediated control of C. burnetii replication might be the first step towards the development of host directed intervention measures to mitigate the health burden of this zoonotic agent.

Immunomodulatory activity of manganese dioxide nanoparticles: Promising for novel vaccines and immunotherapeutics

Manganese (Mn), a nutrient inorganic trace element, is necessary for a variety of physiological processes of animal body due to their important roles in oxidative regulation effects and other aspects of activities. Moreover, manganese ion (Mn²⁺) has widely reported to be crucial for the regulations of different immunological responses, thus showing promising application as potential adjuvants and immunotherapeutics. Taking the advantages of Mn-based biological and immunological activities, Manganese dioxide nanoparticles (MnO₂ NPs) are a new type of inorganic nanomaterials with numerous advantages, including simple preparation, low cost, environmental friendliness, low toxicity, biodegradable metabolism and high bioavailability. MnO₂ NPs, as a kind of drug carrier, have also shown the ability to catalyze hydrogen peroxide (H₂O₂) to produce oxygen (O₂) under acidic conditions, which can enhance the efficacy of radiotherapy, chemotherapy and other therapeutics for tumor treatment by remodeling the tumor microenvironment. More importantly, MnO₂ NPs also play important roles in immune regulations both in innate and adaptive immunity. In this review, we summarize the biological activities of Manganese, followed by the introduction for the biological and medical functions and mechanisms of MnO₂ NPs. What's more, we emphatically discussed the immunological regulation effects and mechanisms of MnO₂ NPs, as well as their potentials to serve as adjuvants and immunomodulators, which might benefit the development of novel vaccines and immunotherapies for more effective disease control.

Regulation of cells of the arterial wall by hypoxia and its role in the development of atherosclerosis

The cell's response to hypoxia depends on stabilization of the hypoxia-inducible factor 1 complex and transactivation of nuclear factor kappa-B (NF-κB). HIF target gene transcription in cells resident to atherosclerotic lesions adjoins a complex interplay of cytokines and mediators of inflammation affecting cholesterol uptake, migration, and inflammation. Maladaptive activation of the HIF-pathway and transactivation of nuclear factor kappa-B causes monocytes to invade early atherosclerotic lesions, maintaining inflammation and aggravating a low-oxygen environment. Meanwhile HIF-dependent upregulation of the ATP-binding cassette transporter ABCA1 causes attenuation of cholesterol efflux and ultimately macrophages becoming foam cells. Hypoxia facilitates neovascularization by upregulation of vascular endothelial growth factor (VEGF) secreted by endothelial cells and vascular smooth muscle cells lining the arterial wall destabilizing the plaque. HIF-knockout animal models and inhibitor studies were able to show beneficial effects on atherogenesis by counteracting the HIF-pathway in the cell wall. In this review the authors elaborate on the up-to-date literature on regulation of cells of the arterial wall through activation of HIF-1α and its effect on atherosclerotic plaque formation.

Genome-wide identification of antisense lncRNAs and their association with susceptibility to Flavobacterium psychrophilum in rainbow trout

Eukaryotic genomes encode long noncoding natural antisense transcripts (lncNATs) that have been increasingly recognized as regulatory members of gene expression. Recently, we identified a few antisense transcripts correlating in expression with immune-related genes. However, a systematic genome-wide analysis of lncNATs in rainbow trout is lacking. This study used 134 RNA-Seq datasets from five different projects to identify antisense transcripts. A total of 13,503 lncNATs were identified genome-wide. About 75% of lncNATs showed multiple exons compared to 36.5% of the intergenic lncRNAs. RNA-Seq datasets from resistant, control, and susceptible rainbow trout genetic lines with significant differences in survival rate following Flavobacterium psychrophilum (Fp) infection were analyzed to investigate the potential role of the lncNATs during infection. Twenty-four pairwise comparisons between the different genetic lines, infectious status, and time points revealed 581 differentially expressed (DE) lncNATs and 179 differentially used exons (DUEs). Most of the DE lncNATs strongly and positively correlated in expression with their corresponding sense transcripts across 24 RNA-Seq datasets. LncNATs complementary to genes related to immunity, muscle contraction, proteolysis, and iron/heme metabolism were DE following infection. LncNATs complementary to hemolysis-related genes were DE in the resistant fish compared to susceptible fish on day 5 post-infection, suggesting enhanced clearance of free hemoglobin (Hb) and heme and increased erythropoiesis. LncNATs complementary to hepcidin, a master negative regulator of the plasma iron concentration, were the most downregulated lncNATs on day 5 of bacterial infection in the resistant fish. Ninety-four DE lncNAT, including five complementary to hepcidin, are located within 26 QTL regions previously identified in association with bacterial cold water disease (BCWD) in rainbow trout. Collectively, lncNATs are involved in the molecular architecture of fish immunity and should be further investigated for potential applications in genomic selection and genetic manipulation in aquaculture.

Campylobacter jejuni induces differentiation of human neutrophils to the CD16hi /CD62Llo subtype

The discovery of neutrophil subtypes has expanded what is known about neutrophil functions, yet there is still much to learn about the role of these subtypes during bacterial infection. We investigated whether Campylobacter jejuni induced differentiation of human neutrophils into the hypersegmented, CD16^hi /CD62L^lo subtype. In addition, we investigated whether C. jejuni-dependent differentiation of this neutrophil subtype induced cancer-promoting activities of human T cells and colonocytes, which were observed in other studies of hypersegmented, CD16^hi /CD62L^lo neutrophils. We found that C. jejuni causes a significant shift in human neutrophil populations to the hypersegmented, CD16^hi /CD62L^lo subtype and that those populations exhibit delayed apoptosis, elevated arginase-1 expression, and increased reactive oxygen species production. Furthermore, incubation of C. jejuni-infected neutrophils with human T cells resulted in decreased expression of the ζ-chain of the TCR, which was restored upon supplementation with exogenous l-arginine. In addition, incubation of C. jejuni-infected neutrophils with human colonocytes resulted in increased HIF-1α stabilization and NF-κB activation in those colonocytes, which may result in the up-regulation of protumorigenic genes.

Lactose azocalixarene drug delivery system for the treatment of multidrug-resistant pseudomonas aeruginosa infected diabetic ulcer

Diabetic wound is one of the most intractable chronic wounds that is prone to bacterial infection. Hypoxia is an important feature in its microenvironment. However, it is challenging for antimicrobial therapy to directly apply the existing hypoxia-responsive drug delivery systems due to the active targeting deficiency and the biofilm obstacle. Herein, we customizes a hypoxia-responsive carrier, lactose-modified azocalix[4]arene (LacAC4A) with the ability to actively target and inhibit biofilm. By loading ciprofloxacin (Cip), the resultant supramolecular nanoformulation Cip@LacAC4A demonstrates enhanced antibacterial efficacy resulting from both the increased drug accumulation and the controlled release at the site of infection. When applied on diabetic wounds together with multidrug-resistant Pseudomonas aeruginosa infection in vivo, Cip@LacAC4A induces definitely less inflammatory infiltration than free Cip, which translates into high wound healing performance. Importantly, such design principle provides a direction for developing antimicrobial drug delivery systems.

Bacterial conversion of a host weapon into a nutritional signal

Bacteria engulfed by phagocytic cells must resist oxidation damage and adapt to cellular hypoxia, but the mechanisms involved in this process are not completely elucidated. Recent work by Kim et al. in the Journal of Biological Chemistry investigated how the intracellular pathogen Salmonella enterica activates gene expression required to counteract oxidative damage. The authors show that this bacterium utilizes host oxidative molecules to activate regulatory proteins that enhance the production of effector molecules, counteracting the host weapon NADPH oxidase and inducing a protective response.

Loss of Vhl alters trabecular bone loss during S. aureus osteomyelitis in a cell-specific manner

Osteomyelitis, or bone infection, is a major complication of accidental trauma or surgical procedures involving the musculoskeletal system. Staphylococcus aureus is the most frequently isolated pathogen in osteomyelitis and triggers significant bone loss. Hypoxia-inducible factor (HIF) signaling has been implicated in antibacterial immune responses as well as bone development and repair. In this study, the impact of bone cell HIF signaling on antibacterial responses and pathologic changes in bone architecture was explored using genetic models with knockout of either Hif1a or a negative regulator of HIF-1α, Vhl. Deletion of Hif1a in osteoblast-lineage cells via Osx-Cre (Hif1aΔOB ) had no impact on bacterial clearance or pathologic changes in bone architecture in a model of post-traumatic osteomyelitis. Knockout of Vhl in osteoblast-lineage cells via Osx-Cre (VhlΔOB ) caused expected increases in trabecular bone volume per total volume (BV/TV) at baseline and, intriguingly, did not exhibit an infection-mediated decline in trabecular BV/TV, unlike control mice. Despite this phenotype, bacterial burdens were not affected by loss of Vhl. In vitro studies demonstrated that transcriptional regulation of the osteoclastogenic cytokine receptor activator of NF-κB ligand (RANKL) and its inhibitor osteoprotegerin (OPG) is altered in osteoblast-lineage cells with knockout of Vhl. After observing no impact on bacterial clearance with osteoblast-lineage conditional knockouts, a LysM-Cre model was used to generate Hif1aΔMyeloid and VhlΔMyeloid mouse models to explore the impact of myeloid cell HIF signaling. In both Hif1aΔMyeloid and VhlΔMyeloid models, bacterial clearance was not impacted. Moreover, minimal impacts on bone architecture were observed. Thus, skeletal HIF signaling was not found to impact bacterial clearance in our mouse model of post-traumatic osteomyelitis, but Vhl deletion in the osteoblast lineage was found to limit infection-mediated trabecular bone loss, possibly via altered regulation of RANKL-OPG gene transcription.

Gold Nanoclusters-Based NIR-II Photosensitizers with Catalase-like Activity for Boosted Photodynamic Therapy

Photodynamic therapy (PDT) under fluorescence imaging as a selective and non-invasive treatment approach has been widely applied for the therapy of cancer and bacterial infections. However, its treatment efficiency is hampered by high background fluorescence in the first near-infrared window (NIR-I, 700–900 nm) and oxygen-dependent photosensitizing activity of traditional photosensitizers. In this work, we employ gold nanoclusters (BSA@Au) with the second near-infrared (NIR-II, 1000–1700 nm) fluorescence and catalase-like activity as alternative photosensitizers to realize highly efficient PDT. The bright NIR-II fluorescence of BSA@Au enables the visualization of PDT for tumor with a high signal-to-background ratio (SBR = 7.3) in 4T1 tumor-bearing mouse models. Furthermore, the catalase-like activity of BSA@Au endows its oxygen self-supplied capability, contributing to a five-fold increase in the survival period of tumor-bearing mice receiving boosted PDT treatment compared to that of the control group. Moreover, we further demonstrate that BSA@Au-based PDT strategy can be applied to treat bacterial infections. Our studies show the great potential of NIR-II BSA@Au as a novel photosensitizer for boosted PDT against cancer and bacterial infections.

Structural Analysis of Mitochondrial Dynamics-From Cardiomyocytes to Osteoblasts: A Critical Review

Mitochondria play a crucial role in cell physiology and pathophysiology. In this context, mitochondrial dynamics and, subsequently, mitochondrial ultrastructure have increasingly become hot topics in modern research, with a focus on mitochondrial fission and fusion. Thus, the dynamics of mitochondria in several diseases have been intensively investigated, especially with a view to developing new promising treatment options. However, the majority of recent studies are performed in highly energy-dependent tissues, such as cardiac, hepatic, and neuronal tissues. In contrast, publications on mitochondrial dynamics from the orthopedic or trauma fields are quite rare, even if there are common cellular mechanisms in cardiovascular and bone tissue, especially regarding bone infection. The present report summarizes the spectrum of mitochondrial alterations in the cardiovascular system and compares it to the state of knowledge in the musculoskeletal system. The present paper summarizes recent knowledge regarding mitochondrial dynamics and gives a short, but not exhaustive, overview of its regulation via fission and fusion. Furthermore, the article highlights hypoxia and its accompanying increased mitochondrial fission as a possible link between cardiac ischemia and inflammatory diseases of the bone, such as osteomyelitis. This opens new innovative perspectives not only for the understanding of cellular pathomechanisms in osteomyelitis but also for potential new treatment options.

Field Experiences with Handheld Diagnostic Devices to Triage Children under Five Presenting with Severe Febrile Illness in a District Hospital in DR Congo

As part of a field study (NCT04473768) in children presenting with severe febrile illness to Kisantu hospital (DR Congo), we retrospectively compiled user experiences (not performance) with handheld diagnostic devices assisting triage: tympanic thermometer, pulse oximeter (measuring heart rate, respiratory rate and oxygen saturation), hemoglobinometer and glucometer. Guidance documents for product selection were generic and scattered. Stock rupture, market withdrawal and unaffordable prices interfered with procurement. Challenges at implementation included environmental temperature, capillary blood sampling (antisepsis, order of multiple tests, filling microcuvettes and glucose strips), calibration (environmental temperature, cold chain) and liability-oriented communication with a manufacturer. Instructions for use were readable and contained symbol keys; two devices had printed French-language instructions. Shortcomings were poor integration of figures with text and distinct procedures for the oximeter and its sensor. Usability interview revealed appreciations for quick results, visibility of the display and memory function (three devices) but also problems of capillary blood sample transfer, cleaning, too long of a time-to-results (respiratory rate) and size, fitting and disposal of thermometer probes. Pictorial error messages were preferred over alphanumeric error codes but interpretation of symbols was poor. Alarm sounds of the oximeter caused unrest in children and caretakers perceived the device as associated with poor prognosis.

Formation of Neutrophil Extracellular Traps by Reduction of Cellular Cholesterol Is Independent of Oxygen and HIF-1α

Formation of neutrophil extracellular traps (NETs) is a two-faced innate host defense mechanism, which, on the one hand, can counteract microbial infections, but on the other hand, can contribute to massive detrimental effects on the host. Cholesterol depletion from the cellular membrane by Methyl-β-cyclodextrin (MβCD) is known as one of the processes initiating NET formation. Since neutrophils mainly act in an inflammatory environment with decreased, so-called hypoxic, oxygen conditions, we aimed to study the effect of oxygen and the oxygen stress regulator hypoxia-inducible factor (HIF)-1α on cholesterol-dependent NET formation. Thus, murine bone marrow-derived neutrophils from wild-type and HIF-knockout mice or human neutrophils were stimulated with MβCD under normoxic (21% O₂) compared to hypoxic (1% O₂) conditions, and the formation of NETs were studied by immunofluorescence microscopy. We found significantly induced NET formation after treatment with MβCD in murine neutrophils derived from wild-type as well as HIF-1α KO mice at both hypoxic (1% O₂) as well as normoxic (21% O₂) conditions. Similar observations were made in freshly isolated human neutrophils after stimulation with MβCD or statins, which block the HMG-CoA reductase as the key enzyme in the cholesterol metabolism. HPLC was used to confirm the reduction of cholesterol in treated neutrophils. In summary, we were able to show that NET formation via MβCD or statin-treatment is oxygen and HIF-1α independent.

From the Dish to the Real World: Modeling Interactions between the Gut and Microorganisms in Gut Organoids by Tailoring the Gut Milieu

The advent of human intestinal organoid systems has revolutionized the way we understand the interactions between the human gut and microorganisms given the host tropism of human microorganisms. The gut microorganisms have regionality (i.e., small versus large intestine) and the expression of various virulence factors in pathogens is influenced by the gut milieu. However, the culture conditions, optimized for human intestinal organoids, often do not fully support the proliferation and functionality of gut microorganisms. In addition, the regional identity of human intestinal organoids has not been considered to study specific microorganisms with regional preference. In this review we provide an overview of current efforts to understand the role of microorganisms in human intestinal organoids. Specifically, we will emphasize the importance of matching the regional preference of microorganisms in the gut and tailoring the appropriate luminal environmental conditions (i.e., oxygen, pH, and biochemical levels) for modeling real interactions between the gut and the microorganisms with human intestinal organoids.

Silver Peroxide Nanoparticles for Combined Antibacterial Sonodynamic and Photothermal Therapy

Metal peroxide nanoparticles designed to elevate the oxidative stress are considered a promising nanotherapeutics in biomedical applications, including chemotherapy, photodynamic therapy, and bacterial disinfection. However, their lack of specificity towards the therapeutic target can cause toxic side effects to healthy tissues. Here, silver peroxide nanoparticles (Ag₂ O₂ NPs) capable of controlled reactive oxygen species (ROS) release are synthesized. The release of bactericidal Ag⁺ ions and ROS is strictly regulated by external stimuli of ultrasound (US) and near-infrared (NIR) light. In vitro and in vivo investigations show that the Ag₂ O₂ NPs present enhanced antibacterial and antibiofilm capabilities with a killing efficiency >99.9999% in 10 min, significantly accelerate multi-drug resistant Staphylococcus aureus infected skin wound closure with excellent cytocompatibility and hemocompatibility. This work not only provides the first paradigm for fabricating silver peroxide nanoparticle but also introduces a highly efficient noninvasive and safe therapeutic modality for combating bacterial infectious diseases.

Analysis of Salivary Microbiome and Its Association With Periodontitis in Patients With Obstructive Sleep Apnea

Objectives

This study aimed to analyze the periodontal conditions of patients with obstructive sleep apnea (OSA) in relation to the salivary microbiome.

Materials and Methods

In total, 54 male adults (27 with OSA, 27 controls) completed this cross-sectional study. All participants were monitored by overnight polysomnography (PSG) and underwent full-mouth periodontal examination. Saliva samples were then collected, and the microbial 16S ribosomal RNA gene was sequenced. The data were analyzed to determine the microbial distribution and the community structure of the two groups.

Results

Demonstrated by alpha and beta diversity, the OSA group had a lower microbial richness and a lower observed species than the controls. There was no significant difference in the microbial species diversity or evenness between the OSA and the non-OSA groups. The OSA group had fewer operational taxonomic units (OTUs), and the distribution of microbiome showed that several gram-positive bacteria had higher abundance in the OSA group. As for periodontal pathogens, the relative abundance of Prevotella was significantly increased in the OSA group. No significant difference was observed in the relative abundance of other pathogens at either the genus or species level.

Conclusions

The salivary microbial community structure was altered in patients with OSA in terms of species richness and trans-habitat diversity, along with an increase in Prevotella, a specific periodontal pathogen. These findings might explain the high prevalence of periodontitis in OSA patients.

Application of serum exosomal hypoxia-inducible factor-1 alpha (HIF-1α) as potential circulating biomarker for bacterial peritonitis

Bacterial peritonitis is a severe disease that diagnosis remains challenging for clinicians. Measuring biomarkers might be a rapid diagnostic method. The objective of this study was to analyze and evaluate the dynamic changes in HIF-1α concentration in serum exosomes during bacterial peritonitis. The pre-clinical application value of serum exosomal HIF-1α was evaluated via imipenem and cilastatin sodium (ICS) intervention in the bacterial peritonitis model. The new colorimetric method to quantitate dynamic expression changes of HIF-1α in serum exosomes during bacterial peritonitis was established by our team via using the gold seed-coated with aptamer-functionalized Au @ Au core-shell peroxidase mimic. The typical inflammatory cytokines of bacterial peritonitis were also measured. Following intramuscular administration with ICS, In-Vivo Xtreme imaging system was used to visualize abdominal infection extent. Meanwhile, HIF-1α concentration in rat serum exosomes and pro-inflammatory factors levels in serum were detected. The serum typical inflammatory cytokines levels were elevated in GFP-labelled E.coli induced bacterial peritonitis. The serum exosomal HIF-1α levels clearly increased at 12 h, reached the peak during 24-48 h, and then gradually decreased at 72 h. Following intramuscular administration with ICS, the abdominal infection extent, HIF-1α concentration in serum exosomes, and the serum pro-inflammatory factors levels were reduced at 24 h in GFP-labelled E. coli induced bacterial peritonitis model. The serum exosomal HIF-1α can be used as a biomarker in the early stage of bacterial peritonitis, which might provide the basic research in the pre-clinical for further predicting and monitoring the pathological process of bacterial peritonitis.

Design of a synthesis-friendly hypoxia-responsive promoter for cell-based therapeutics

Towards the goal of making 'smart' cell therapies, one that recognizes disease conditions (e.g. hypoxia) and then produces mitigating biologics, it is important to develop suitable promoters. Currently, hypoxia responsive promoters are composed of strongly repeated sequences containing hypoxia response elements upstream of a minimal core promoter. Unfortunately, such repeated sequences have inherent genomic instability that may compromise the long-term consistency of cell-based therapeutics. Thus, we designed a synthesis-friendly hypoxia-inducible promoter (named SFHp) that has GC content between 25% and 75% and no repeats greater than 9 base pairs. In HEK293 cells stably integrated with genes regulated by synthetic SFHp, we demonstrated inducible reporter expression with fluorescent proteins, cell morphology rewiring with our previously engineered RhoA protein and intercellular cell signalling with secreted cytokines. These experiments exemplify the potential usage of SFHp in cell-based therapeutics with integrated genetic circuits that inducibly respond to the disease microenvironment.

Identification of a gut microbiota member that ameliorates DSS-induced colitis in intestinal barrier enhanced Dusp6-deficient mice

Strengthening the gut epithelial barrier is a potential strategy for management of gut microbiota-associated illnesses. Here, we demonstrate that dual-specificity phosphatase 6 (Dusp6) knockout enhances baseline colon barrier integrity and ameliorates dextran sulfate sodium (DSS)-induced colonic injury. DUSP6 mutation in Caco-2 cells enhances the epithelial feature and increases mitochondrial oxygen consumption, accompanied by altered glucose metabolism and decreased glycolysis. We find that Dusp6-knockout mice are more resistant to DSS-induced dysbiosis, and the cohousing and fecal microbiota transplantation experiments show that the gut/fecal microbiota derived from Dusp6-knockout mice also confers protection against colitis. Further culturomics and mono-colonialization experiments show that one gut microbiota member in the genus Duncaniella confers host protection from DSS-induced injury. We identify Dusp6 deficiency as beneficial for shaping the gut microbiota eubiosis necessary to protect against gut barrier-related diseases.