Salivary microbiome in patients undergoing hemodialysis and its associations with the duration of the dialysis

Association between salivary microbiota and tacrolimus pharmacokinetic variability in kidney transplant

Kidney transplantation (KT) serves as a highly effective treatment for end-stage renal disease (ESRD). Nonetheless, the administration of tacrolimus, a commonly used immunosuppressant in KT, faces challenges due to the lack of dependable biomarkers for its efficacy and the considerable variability in tacrolimus pharmacokinetics (TacIPV). In this study, 183 saliva samples from 48 KT recipients under tacrolimus therapy, alongside 9 healthy control samples, were subjected to 16S rRNA sequencing. The analysis revealed significant differences in the composition of salivary microbiota among KT recipients, patients with ESRD, and healthy controls. Moreover, trough blood concentrations (C0) of tacrolimus were associated with alterations in microbiota composition. Notably, Capnocytophage consistently exhibited a negative correlation in both group-level and individual trends. Furthermore, distinct taxa were identified that effectively distinguished recipients with varying TacIPV, as demonstrated by a cross-validation random forest model (mean AUC = 0.7560), with Anaerolinea emerging as a prominent contributor to the classifier. These findings suggest that salivary microbiota is closely linked to tacrolimus C0 levels and could aid clinicians in differentiating KT recipients based on TacIPV.

Prediction of delayed graft function by early salivary microbiota following kidney transplantation

Delayed graft function (DGF) is a frequently observed complication following kidney transplantation (KT). Our prior research revealed dynamic shifts in salivary microbiota post-KT with immediate graft function (IGF), yet its behavior during DGF remains unexplored. Five recipients with DGF and 35 recipients with IGF were enrolled. Saliva samples were collected during the perioperative period, and 16S rRNA gene sequencing was performed. The salivary microbiota of IGFs changed significantly and gradually stabilized with the recovery of renal function. The salivary microbiota composition of DGFs was significantly different from that of IGFs, although the trend of variation appeared to be similar to that of IGFs. Salivary microbiota that differed significantly between patients with DGF and IGF at 1 day after transplantation were able to accurately distinguish the two groups in the randomForest algorithm (accuracy = 0.8333, sensitivity = 0.7778, specificity = 1, and area under curve = 0.85), with Selenomonas playing an important role. Bacteroidales (Spearman's r =  - 0.4872 and p = 0.0293) and Veillonella (Spearmen's r =  - 0.5474 and p = 0.0125) were significantly associated with the serum creatinine in DGF patients. Moreover, the significant differences in overall salivary microbiota structure between DGF and IGF patients disappeared upon long-term follow-up. This is the first study to investigate the dynamic changes in salivary microbiota in DGFs. Our findings suggested that salivary microbiota was able to predict DGF in the early stages after kidney transplantation, which might help the perioperative clinical management and early-stage intervention of kidney transplant recipients. KEY POINTS: • Salivary microbiota on the first day after KT could predict DGF. • Alterations in salivary taxa after KT are related to recovery of renal function.

Fortified synbiotic dessert for improving malnutrition in hemodialysis patients: A randomized, double-blind, controlled trial

As dysbiosis of gut microbiota is recognized as a major risk factor for malnutrition in hemodialysis (HD) patients, we aimed to assess the effects of fortified synbiotic dessert on malnutrition, oxidative stress, inflammation, and quality of life in patients undergoing hemodialysis. A total of 50 hemodialysis patients were randomized into two groups of intervention and control to consume either 50 g of synbiotic dessert fortified with vitamin D (1000 IU) and calcium (500 mg) (FSD) or 50 g of control dessert (CD) for 8 weeks, respectively. Changes in nutritional status [Subjective Global Assessment (SGA)], anthropometric measures, malondialdehyde (MDA), total antioxidant capacity (TAC), high-sensitivity C-reactive protein (hs-CRP), ferritin, biochemistry [serum albumin, vitamin D, creatinine, blood urea nitrogen (BUN), complete blood count (CBC), and electrolytes], and quality of life were assessed before and at the end of the trial. The SGA scores and serum ferritin levels decreased significantly in the FSD group compared to the control group (p = .01 and p = .03, respectively). Regarding other markers, no statistically significant changes were found comparing the two groups. This novel fortified synbiotic dessert as a functional food may be effective in reducing the severity of malnutrition by improving SGA score in short term in hemodialysis patients. Thus, it is suggested to do further studies to elucidate the possible mechanisms related to the effects of this dessert on microbiota, skeletal muscle mass, and inflammation in HD in long term.

Salivary microbiome in kidney diseases: A narrative review

Many research has been conducted since the microbiota's discovery that have focused on the role it plays in health and disease. Microbiota can be divided into categories like intestinal, oral, respiratory, and skin microbiota based on the specific localized areas. To maintain homeostasis and control immunological response, the microbial populations live in symbiosis with the host. On the other hand, dysbiosis of the microbiota can cause diseases including kidney diseases and the deregulation of body functioning. We discuss the current understanding of how various kidney diseases are caused by the salivary microbiome (SM) in this overview. First, we review the studies on the salivary microbiota in diverse clinical situations. The importance of the SM in diabetic kidney disease, chronic kidney disease, membranous nephropathy, and IgA nephropathy is next highlighted. We conclude that the characteristics of the SM of patients with various kidney diseases have revealed the potential of salivary microbial markers as noninvasive tool for the detection of various kidney diseases.

Saliva as Biomarker for Oral and Chronic Degenerative Non-Communicable Diseases

Saliva is a very complex fluid and it is essential to maintain several physiological processes and functions, including oral health, taste, digestion and immunological defenses. Saliva composition and the oral microbiome can be influenced by several factors, like diet and smoking habits, and their alteration can represent an important access point for pathogens and, thus, for systemic illness onset. In this review, we explore the potentiality of saliva as a new tool for the early detection of some pathological conditions, such as oral diseases, chronic degenerative non-communicable diseases, among these chronic kidney disease (CKD). We also examined the possible correlation between oral and systemic diseases and oral and gut microbiota dysbiosis. In particular, we deeply analyzed the relationship between oral diseases and CKD. In this context, some salivary parameters can represent a new device to detect either oral or systemic pathologies. Moreover, the positive modulation of oral and gut microbiota induced by prebiotics, postbiotics, or symbiotics could represent a new possible adjuvant therapy in the clinical management of oral diseases and CKD.

Association between salivary microbiota and renal function in renal transplant patients during the perioperative period

Introduction

Renal transplantation is an effective treatment for the end stage renal disease (ESRD). However, how salivary microbiota changes during perioperative period of renal transplant recipients (RTRs) has not been elucidated.

Methods

Five healthy controls and 11 RTRs who had good recovery were enrolled. Saliva samples were collected before surgery and at 1, 3, 7, and 14 days after surgery. 16S rRNA gene sequencing was performed.

Results

There was no significant difference in the composition of salivary microbiota between ESRD patients and healthy controls. The salivary microbiota of RTRs showed higher operational taxonomic units (OTUs) amount and greater alpha and beta diversity than those of ESRD patients and healthy controls, but gradually stabilized over time. At the phylum level, the relative abundance of Actinobacteria, Tenericutes and Spirochaetes was about ten times different from ESRD patients or healthy controls for RTRs overall in time. The relative abundance of Bacteroidetes, Fusobacteria, Patescibacteria, Leptotrichiaceae and Streptococcaceae was correlated with serum creatinine (Scr) after renal transplantation.

Discussion

In short, salivary microbiota community altered in the perioperative period of renal transplantation and certain species of salivary microbiota had the potential to be a biomarker of postoperative recovery.

[Research Progress in the Correlation Between Oral Microbiota and Chronic Kidney Disease]

Chronic kidney disease (CKD), one of the common clinical urological diseases, is increasingly more prevalent in recent years and has emerged as a major concern of public health around the globe. The continuous recurrence of CKD caused by renal function impairment leads eventually to irreversible renal failure and severe systemic complications, which causes severe negative impact on the quality of life of the patient. As an essential component of human microbiome, oral microbiota plays a major role in maintaining health, and there has been research suggesting close association between oral dysbiosis and CKD. It is therefore of great clinical significance to understand the correlation between CKD and oral microbiota. Herein, we reviewed the characteristics of oral microbiota of CKD patients, the possible mechanisms of oral microbiota's involvement in the pathogenesis and development of CKD, and the latest research findings on oral dysbiosis and CKD, with a view to finding new approaches to early prevention and control of CKD through oral microbial targets.

Using Nanopore Sequencing to Obtain Complete Bacterial Genomes from Saliva Samples

Obtaining complete, high-quality reference genomes is essential to the study of any organism. Recent advances in nanopore sequencing, as well as genome assembly and analysis methods, have made it possible to obtain complete bacterial genomes from metagenomic (i.e., multispecies) samples, including those from the human microbiome. In this study, methods are presented to obtain complete bacterial genomes from human saliva using complementary Oxford Nanopore (ONT) and Illumina sequencing. Applied to 3 human saliva samples, these methods resulted in 11 complete bacterial genomes: 3 Saccharibacteria clade G6 (also known as Ca. Nanogingivalaceae HMT-870), 1 Saccharibacteria clade G1 HMT-348, 2 Rothia mucilaginosa, 2 Actinomyces graevenitzii, 1 Mogibacterium diversum, 1 Lachnospiraceae HMT-096, and 1 Lancefieldella parvula; and one circular chromosome of Ruminococcaceae HMT-075 (which likely has at least 2 chromosomes). The 4 Saccharibacteria genomes, as well as the Actinomyces graeventizii genomes, represented the first complete genomes from their respective bacterial taxa. Aside from the complete genomes, the assemblies contained 147 contigs of over 500,000 bp each and thousands of smaller contigs, together representing a myriad of additional draft genomes including many which are likely nearly complete. The complete genomes enabled highly accurate pangenome analysis, which identified unique and missing features of each genome compared to its closest relatives with complete genomes available in public repositories. These features provide clues as to the lifestyle and ecological role of these bacteria within the human oral microbiota, which will be particularly useful in designing future studies of the taxa that have never been isolated or cultivated. IMPORTANCE Obtaining complete and accurate genomes is crucial to the study of any organism. Previously, obtaining complete genomes of bacteria, including those of the human microbiome, frequently required isolation of the organism, as well as low-throughput, manual sequencing methods to resolve repeat regions. Advancements in long-read sequencing technologies, including Oxford Nanopore (ONT), have made it possible to obtain complete, closed bacterial genomes from metagenomic samples. This study reports methods to obtain complete genomes from the human oral microbiome using complementary ONT and Illumina sequencing of saliva samples. Eleven complete genomes were obtained from 3 human saliva samples, with genomes of Saccharibacteria HMT-870, Saccharibacteria HMT-348, and Actinomyces graeventzii being the first complete genomes from their respective taxa. Obtaining complete bacterial genomes in a high-throughput manner will help illuminate the metabolic and ecological roles of important members of the human microbiota, particularly those that have remained recalcitrant to isolation and cultivation.

Salivary microbiome in chronic kidney disease: what is its connection to diabetes, hypertension, and immunity?

BACKGROUND

The association between oral dysbiosis and chronic kidney disease (CKD) has gained increasing attention in recent years. Diabetes and hypertension are the most common conditions in CKD. However, a case-control study with matched confounding variables on the salivary microbiome in CKD and the influence of diabetes and hypertension on the microbiome has never been reported.

METHODS

In our study, we compared the salivary microbiome profile between patients with CKD and healthy controls (HC) using 16S ribosomal DNA sequencing and examine its association with diabetes, hypertension, and immunity.

RESULTS

We observed that the bacterial community was skewed in the saliva of CKD, with increased Lautropia and Pseudomonas, and decreased Actinomyces, Prevotella, Prevotella 7, and Trichococcus. No difference in the bacterial community between the CKD patients complicated with and without diabetes, and between those with and without hypertension. Prevotella 7 declined in CKD patients with/without hypertension with respect to HC, while Pseudomonas increased in CKD patients with/without hypertension. Pseudomonas was negatively associated with immunoglobin G in CKD patients. Both CKD patients with positive and negative antistreptolysin O had declined Prevotella 7 and Trichococcus compared to HC, whereas increased Pseudomonas.

CONCLUSIONS

Our study identifies a distinct bacterial saliva microbiome in CKD patients characterized by alteration in composition. We unravel here that the co-occurrence diseases of diabetes and hypertension are not associated with specific bacterial alterations, suggesting that bacterial dysbiosis in saliva plays a role in renal damage regardless of the occurrence of diabetes and hypertension.

Salivary microbiota analysis of patients with membranous nephropathy

The oral microbiota are closely related to human health. Nonetheless, to the best of our knowledge, their relationship with membranous nephropathy (MN) remains unstudied. The saliva microbiota collected from 22 patients with MN and 15 healthy controls were analyzed by next-generation sequencing, and bioinformatics analysis of the 16S ribosomal RNA gene was subsequently carried out. The Chao1 and Shannon indices in patients with MN were higher than those in healthy controls. Analysis of similarities revealed that the oral microbiota in the patient group were significantly different from those in the healthy controls. At the genus level, the abundance of Alloprevotella, Granulicatella, Prevotella, Streptococcus and Prevotella_7 was markedly higher in patients with MN than in healthy controls. Six operational taxonomic units (OTUs; OTU5, OTU28, OTU9, OTU15, OTU33 and OTU38) were found to be markedly correlated with the clinical factors creatinine, proteinuria in 24 h, estimated glomerular filtration rate and systolic blood pressure. A total of 28 Kyoto Encyclopedia of Genes and Genomes pathways were obtained from the significant OTUs. The oral microbiota of patients with MN were investigated and it was found that OTU5, OTU28, OTU9, OTU15, OTU33 and OTU38 may be used as biomarkers. The present findings may assist in the diagnosis of patients with MN.

Association between periodontitis and chronic kidney disease

Periodontitis and chronic kidney disease are chronic conditions with high community prevalence across the world. Patients with chronic kidney disease have been noted to have a high burden of periodontitis, and several shared risk factors have been associated with the prevalence and severity of both conditions. However, the precise relationship between the two conditions, and the extent to which each may contribute to the development of the other, remains a matter of debate. The goals of the present work were to: (a) provide the most current and relevant literature overview of the association between periodontitis and chronic kidney disease; (b) explore mechanisms underlying this association; and (c) determine if evidence exists for an independent association between these conditions. We also assessed whether improved oral hygiene and periodontal treatment could reduce the risk of developing chronic kidney disease and, if so, what protocols these strategies involve. Finally, we aimed to reveal gaps in our current knowledge to delineate the directions of future research. Although the exact relationship between these two conditions has not yet been defined, we highlight the importance of the interprofessional interaction between dental practitioners and the nephrology team and the importance of oral health assessment in the management of chronic kidney disease.

Natural Bioactive Compounds in the Management of Oral Diseases in Nephropathic Patients

Among the chronic non-communicable degenerative diseases (CDNCDs), chronic kidney disease (CKD) represents a global public health problem. Recent studies demonstrate a mutual cause–effect relationship between CKD and oral diseases, in which the presence of one induces the onset and faster progression of the other. In particular, the oral cavity alterations more frequent in CKD patients are: chronic periodontitis diseases, bone lesions, oral infections, and oral cancer lesions. Currently, a standardized therapy for the treatment of oral diseases is lacking. For this reason, natural bioactive compounds (NBCs), characterized by several health effects, such as antioxidant, antimicrobial, anti-inflammatory and anti-cancer actions, represent a new possible adjuvant therapy in the management of these pathological conditions. Among NBCs, polyphenols play a leading role due to positive modulation of oral microbiota, preventing and correcting oral dysbiosis. Moreover, these compounds exert anti-inflammatory effects, such as inhibiting the production of pro-inflammatory cytokines and the expression of cycloxigenase-2. In this light, the formulation of a new mouthwash/gel/gingival paste, with a high content of polyphenols in association with NBCs characterized by antimicrobial action, could represent a future therapy of oral disease in CKD patients.