Exploring the signature gut and oral microbiome in individuals of specific Ayurveda prakriti.

Diagnosis and treatment of various diseases in Ayurveda, the Indian system of medicine, relies on 'prakriti' phenotyping of individuals into predominantly three constitutions, kapha, pitta and vata. Recent studies propose that microbiome play an integral role in precision medicine. A study of the relationship between prakriti - the basis of personalized medicine in Ayurveda and that of gut microbiome, and possible biomarker of an individual's health, would vastly improve precision therapy. Towards this, we analyzed bacterial metagenomes from buccal (oral microbiome) and fecal (gut microbiome) samples of 272 healthy individuals of various predominant prakritis. Major bacterial genera from gut microbiome included Prevotella, Bacteroides and Dialister while oral microbiome included Streptococcus, Neisseria, Veilonella, Haemophilus, Porphyromonas and Prevotella. Though the core microbiome was shared across all individuals, we found prakriti specific signatures such as preferential presence of Paraprevotella and Christensenellaceae in vata individuals. A comparison of core gut microbiome of each prakriti with a database of 'healthy' microbes identified microbes unique to each prakriti with functional roles similar to the physiological characteristics of various prakritis as described in Ayurveda. Our findings provide evidence to Ayurvedic interventions based on prakriti phenotyping and possible microbial biomarkers that can stratify the heterogenous population and aid in precision therapy.

Infant gut microbiome composition is associated with non-social fear behavior in a pilot study.

Experimental manipulation of gut microbes in animal models alters fear behavior and relevant neurocircuitry. In humans, the first year of life is a key period for brain development, the emergence of fearfulness, and the establishment of the gut microbiome. Variation in the infant gut microbiome has previously been linked to cognitive development, but its relationship with fear behavior and neurocircuitry is unknown. In this pilot study of 34 infants, we find that 1-year gut microbiome composition (Weighted Unifrac; lower abundance of Bacteroides, increased abundance of Veillonella, Dialister, and Clostridiales) is significantly associated with increased fear behavior during a non-social fear paradigm. Infants with increased richness and reduced evenness of the 1-month microbiome also display increased non-social fear. This study indicates associations of the human infant gut microbiome with fear behavior and possible relationships with fear-related brain structures on the basis of a small cohort. As such, it represents an important step in understanding the role of the gut microbiome in the development of human fear behaviors, but requires further validation with a larger number of participants.

Veillonella nakazawae sp. nov., an anaerobic Gram-negative coccus isolated from the oral cavity of Japanese children.

Two strains of previously unknown Gram-negative cocci, T1-7T and S6-16, were isolated from the oral cavity of healthy Japanese children. The two strains showed atypical phenotypic characteristics of members of the genus Veillonella, including catalase production. Sequencing of their 16S rRNA genes confirmed that they belong to genus Veillonella. Under anaerobic conditions, the two strains produced acetic acid and propionic acid as metabolic end-products in a trypticase-yeast extract-haemin medium containing 1 % (w/v) glucose, 1 % (w/v) fructose and 1 % (v/v) sodium lactate. Comparative analysis of the 16S rRNA, dnaK, rpoB and gltA gene sequences revealed that the two strains are phylogenetically homogeneous and comprise a distinct, novel lineage within the genus Veillonella. The sequences from the two strains shared the highest similarity, at 99.9, 95.8, 96.9 and 96.7 %, using the partial 16S rRNA, dnaK, rpoB and gltA gene sequences, respectively, with the type strains of the two most closely related species, Veillonella dispar ATCC 17748T and Veillonella infantium JCM 31738T. Furthermore, strain T1-7T shared the highest average nucleotide identity (ANI) value (94.06 %) with type strain of the most closely related species, V. infantium. At the same time, strain T1-7T showed the highest digital DNA-DNA hybridization (dDDH) value (55.5 %) with the type strain of V. infantium. The two strains reported in this study were distinguished from the previously reported species from the genus Veillonella based on catalase production, partial dnaK, rpoB and gltA sequences, average ANI and dDDH values. Based on these observations, the two strains represent a novel species, for which the name Veillonella nakazawae sp. nov. is proposed. The type strain is T1-7T (JCM 33966T=CCUG 74597T).

The relationship between oral-origin bacteria in the fecal microbiome and albumin-bilirubin grade in patients with hepatitis C.

BACKGROUND: Bacteria of oral origin (BO) in the gut are associated with prognosis in patients with cirrhosis. The Greengenes database (gg_13_8) is widely used in microbiome analysis, but the expanded Human Oral Microbiome Database (eHOMD), a specialized database for BO, can add more detailed information. We used each database to evaluate the relationship between the albumin-bilirubin grade (ALBI) and the microbiome in patients with hepatitis C. METHODS: Eighty patients were classified into the low ALBI group (LA; n = 34) or high ALBI group (HA; n = 46). Isolated DNA from stool was amplified to target the V3-4 regions of 16S rRNA. The microbiomes of the two groups were compared using gg_13_8 or eHOMD. We evaluated the associations between microbiomes and prognoses using Cox proportional hazards models. RESULTS: At the genus level, the two groups differed significantly regarding 6 (gg_13_8) and 7 (eHOMD) types of bacteria. All types except Akkermansia are classified as BO. Both databases showed an increase in Streptococcus and Veillonella. eHOMD showed a decrease in Fusobacterium and an increase in Fretibacterium; both produce various types of short-chain fatty acids. At the species level, the two groups demonstrated significant differences in 2 (gg_13_8) and 6 (eHOMD) bacterial types. Selenomonas noxia and Streptococcus salivarius were related to poor prognosis in univariate analysis. CONCLUSION: The HA group demonstrated increased BO, most of which produce lactic acid or acetic acid. The correlation between the microbiome and metabolism might be related to prognosis. eHOMD was a useful database for analyzing BO.

Nitrite-producing oral microbiome in adults and children.

Recently, it was suggested that the nitrite (NO2-) produced from NO3- by oral bacteria might contribute to oral and general health. Therefore, we aimed to clarify the detailed information about the bacterial NO2-production in the oral biofilm. Dental plaque and tongue-coating samples were collected, then the NO2-producing activity was measured. Furthermore, the composition of the NO2--producing bacterial population were identified using the Griess reagent-containing agar overlay method and molecular biological method. NO2--producing activity per mg wet weight varied among individuals but was higher in dental plaque. Additionally, anaerobic bacteria exhibited higher numbers of NO2--producing bacteria, except in the adults' dental plaque. The proportion of NO2--producing bacteria also varied among individuals, but a positive correlation was found between NO2--producing activity and the number of NO2--producing bacteria, especially in dental plaque. Overall, the major NO2--producing bacteria were identified as Actinomyces, Schaalia, Veillonella and Neisseria. Furthermore, Rothia was specifically detected in the tongue coatings of children. These results suggest that dental plaque has higher NO2--producing activity and that this activity depends not on the presence of specific bacteria or the bacterial compositions, but on the number of NO2--producing bacteria, although interindividual differences were detected.

Dietary Supplementation with Sugar Beet Fructooligosaccharides and Garlic Residues Promotes Growth of Beneficial Bacteria and Increases Weight Gain in Neonatal Lambs.

The proper development of the early gastrointestinal tract (GIT) microbiota is critical for newborn ruminants. This microbiota is susceptible to modification by diverse external factors (such as diet) that can lead to long-lasting results when occurring in young ruminants. Dietary supplementation with prebiotics, ingredients nondigestible and nonabsorbable by the host that stimulate the growth of beneficial GIT bacteria, has been applied worldwide as a potential approach in order to improve ruminant health and production yields. However, how prebiotics affect the GIT microbiota during ruminants' early life is still poorly understood. We investigated the effect of milk supplementation with a combination of two well-known prebiotics, fructooligosaccharides (FOS) from sugar beet and garlic residues (all together named as "additive"), exerted on preweaned lamb growth and the composition of their fecal microbiota, by using 16S rRNA gene amplicon high-throughput sequencing. The results showed a significant increase in the mean daily weight gain of lambs fed with the additive. Lamb fecal microbiota was also influenced by the additive intake, as additive-diet lambs showed lower bacterial diversity and were significantly more abundant in Bifidobacterium, Enterococcus, Lactobacillus and Veillonella. These bacteria have been previously reported to confer beneficial properties to the ruminant, including promotion of growth and health status, and our results showed that they were strongly linked to the additive intake and the increased weight gain of lambs. This study points out the combination of FOS from sugar beet and garlic residues as a potential prebiotic to be used in young ruminants' nutrition in order to improve production yields.

Breastmilk Feeding Practices Are Associated with the Co-Occurrence of Bacteria in Mothers' Milk and the Infant Gut: the CHILD Cohort Study.

Gut microbiota play a critical role in infant health. It is now accepted that breastmilk contains live bacteria from endogenous and exogenous sources, but it remains unclear whether these bacteria transfer to the infant gut and whether this process is influenced by breastmilk feeding practices. Here, we show that certain bacteria, including Streptococcus spp. and Veillonella dispar, co-occur in mothers' milk and their infants' stool, and co-occurrence is reduced when infants receive pumped breastmilk. The relative abundances of commonly shared species are positively correlated between breastmilk and stool. Overall, gut microbiota composition is strongly associated with breastfeeding exclusivity and duration but not breastmilk feeding mode (nursing versus pumping). Moreover, breastmilk bacteria contributed to overall gut microbiota variation to a similar extent as other modifiers of the infant microbiome, such as birth mode. These results provide evidence that breastmilk may transfer bacteria to the infant gut and influence microbiota development.

Breastfeeding may have a long-term effect on oral microbiota: results from the Fin-HIT cohort.

BACKGROUND: Breastfeeding contributes to gastrointestinal microbiota colonization in early life, but its long-term impact is inconclusive. We aimed to evaluate whether the type of feeding during the first six months of life was associated with oral microbiota in adolescence. METHODS: This is a cross-sectional sub-study using baseline information of 423 adolescents from the Finnish Health in Teens (Fin-HIT) cohort. Type of feeding was recalled by parents and dichotomized as (i) No infant formula; (ii) Infant formula (breastmilk + formula or only formula). Saliva microbiota was analysed using 16S rRNA (V3-V4) sequencing. Alpha diversity and beta diversity were compared between feeding type groups using ANCOVA and PERMANOVA, respectively. Differential bacteria abundance was tested using appropriate general linear models. RESULTS: Mean age and body mass index were 11.7 years and 18.0 kg/m2, respectively. The No formula group contained 41% of the participants. Firmicutes (51.0%), Bacteroidetes (19.1%), and Proteobacteria (16.3%) were the most abundant phyla among all participants. Alpha and beta diversity indices did not differ between the two feeding groups. Three Operational Taxonomic Units (OTUs) belonging to Eubacteria and Veillonella genera (phylum Firmicutes) were more abundant in the No formula than in the Infant formula group (log2fold changes/ p - values - 0.920/ < 0.001, - 0.328/ 0.001, - 0.577/ 0.004). CONCLUSION: Differences exist in abundances of some OTUs in adolescence according to feeding type during the first six months of life, but our findings do not support diversity and overall oral microbiota composition in adolescents being affected by early feeding type.

Shifts in the bacterial community of saliva give insights on the relationship between obesity and oral microbiota in adolescents.

The current study aimed at the determination of the impact of obesity on the salivary microbiome in adolescents. Sixty subjects ranging 14-17 years old were enrolled (obese: n = 30-50% females, and normal weight: n = 30-50% females). Stimulated saliva was collected for denaturing gradient gel electrophoresis (DGGE) band patterns and massive 16S rRNA gene sequencing using the Ion Torrent platform. Overall, data analysis revealed that male subjects harbored a higher diverse salivary microbiome, defined by a significant higher richness (32.48 versus 26.74) and diversity (3.36 versus 3.20), higher Simpson values (0.96 versus 0.95) and distinct bacterial community structure considering either sex or condition (p < 0.05). Bacterial community fingerprinting analysis in human saliva showed a positive correlation with increased body mass index (BMI) in adolescents. Veillonella, Haemophilus and Prevotella occurrence was found to be affected by BMI, whereas Neisseria and Rothia occurrence was significantly impacted by sex in obese subjects. Our findings suggest that male and female adolescents may harbor a naturally distinct salivary microbiota and that obesity may specifically have an impact on their oral bacterial community. The potential dysbiotic oral microbiome in obese adolescents raises new insights on the etiology and prevention of future conditions in these populations.

Influence of gastrectomy for gastric cancer treatment on faecal microbiome and metabolome profiles.

OBJECTIVE: Recent evidence points to the gut microbiome's involvement in postoperative outcomes, including after gastrectomy. Here, we investigated the influence of gastrectomy for gastric cancer on the gut microbiome and metabolome, and how it related to postgastrectomy conditions. DESIGN: We performed shotgun metagenomics sequencing and capillary electrophoresis time-of-flight mass spectrometry-based metabolomics analyses on faecal samples collected from participants with a history of gastrectomy for gastric cancer (n=50) and compared them with control participants (n=56). RESULTS: The gut microbiota in the gastrectomy group showed higher species diversity and richness (p<0.05), together with greater abundance of aerobes, facultative anaerobes and oral microbes. Moreover, bile acids such as genotoxic deoxycholic acid and branched-chain amino acids were differentially abundant between the two groups (linear discriminant analysis (LDA) effect size (LEfSe): p<0.05, q<0.1, LDA>2.0), as were also Kyoto Encyclopedia of Genes and Genomes modules involved in nutrient transport and organic compounds biosynthesis (LEfSe: p<0.05, q<0.1, LDA>2.0). CONCLUSION: Our results reveal alterations of gut microbiota after gastrectomy, suggesting its association with postoperative comorbidities. The multi-omic approach applied in this study could complement the follow-up of patients after gastrectomy.

Fulminant gas-forming breast abscess associated with synergistic Veillonella infection.

We present a rare case of a rapidly fulminant and destructive breast abscess with gas production by the synergistic infection of Veillonella and Streptococcus species. To our knowledge, this is the first reported case of Veillonella infection in the breast. Early recognition, empiric antibiotic cover, aggressive surgical debridement, and drainage are necessary to avoid systemic septicemia. Staged reconstructive breast surgery allows for correction any resultant breast deformity.

Salivary microbial analysis of Chinese patients with immunoglobulin A nephropathy.

Microbiota plays an important role in immunoglobulin A (IgA) nephropathy (IgAN); however, the pathogenesis, early diagnosis, and treatment of IgAN remain unclear. The aim of the present study was to develop a preliminary model based on saliva­specific microbes and clinical indicators to facilitate the early diagnosis of IgAN and obtain insights into its treatment. The microbial profile of the saliva of 28 IgAN patients and 25 healthy control subjects was investigated using high­throughput sequencing and bioinformatics analyses of the V4 region in microbial 16S rRNA genes. IgAN patients and healthy subjects did not differ significantly in α­diversity indices (Chao1 and Shannon index) or phylum composition. At the genus level, however, Granulicatella was significantly less abundant in healthy individuals than in IgAN patients, while Prevotella and Veillonella were significantly more abundant in the healthy subjects than in IgAN patients (P<0.05 and P<0.01, respectively). Correlation analysis between biochemical indicators and operational taxonomic units (OTUs) revealed that the glomerular filtration rate was positively correlated with OTU86 and OTU287 at P<0.05, positively correlated with OTU165 at P<0.001, and negatively correlated with OTU455 at P<0.05. The serum creatinine index was negatively correlated with OTU287 at P<0.05 and negatively correlated with OTU165 at P<0.001. The pathological changes were positively correlated with OTU255 at P<0.05, OTU200 at P<0.01, and OTU455 and OTU75 at P<0.001, and negatively correlated with OTU86, OTU287, and OTU788 at P<0.05 and with OTU165 at P<0.01. The differences between Chinese IgAN patients and healthy subjects in terms of OTUs and biochemical indicators were analyzed and a mathematical model to facilitate the clinical diagnosis of IgAN was established.

Dysbiotic salivary microbiota in dry mouth and primary Sjögren's syndrome patients.

OBJECTIVES: Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by reduced lacrimal and salivary secretion. Sicca symptoms together with fatigue and musculoskeletal pain can significantly reduce the patients' quality of life. Furthermore, low salivary secretion may disrupt the oral microbial homeostasis. The aim of this study was to compare the salivary microbiota from pSS patients with patients with sicca symptoms not fulfilling the classification criteria for pSS (non-SS), and with healthy controls without sicca complaints. METHODS: Pellets from centrifuged chewing-stimulated whole saliva from pSS patients (n = 15), non-SS sicca patients (n = 15) and healthy controls (n = 15) were prepared. DNA was extracted and analyzed by 16S rRNA gene sequencing. The acquired sequencing data were performed using the human oral microbiome database (HOMD). RESULTS: We detected 42, 45, and 34 bacterial genera in saliva samples from pSS patients, non-SS sicca patients, and healthy controls, respectively. The most abundant genera in all samples were Prevotella, Veillonella, Streptococcus, and Haemophilus. At species level Streptococcus intermedius, Prevotella intermedia, Fusobacterium nucleatum subsp. vincentii, Porphyromonas endodontalis, Prevotella nancensis, Tannerella spp., and Treponema spp. were detected in the samples from pSS and non-SS only, while Porphyromonas pasteri was mostly found among the healthy controls. CONCLUSION: Our study indicated dysbiosis in the salivary microbiota from pSS and non-SS patients compared to healthy controls. Additionally, the results showed that the salivary microbiome in the pSS group differed significantly from the non-SS group.

Native joint septic arthritis with Veillonella species.

Septic arthritis usually presents as subacute monoarticular inflammation. Majority of the cases in healthy adults are caused by methicillin-resistant Staphylococcus aureus, streptococci and certain gram-negative organisms, mostly in the setting of extremes of ages, trauma or immunosuppression. This is a case of a healthy adult with a sudden onset of inflammation of the knee joint, being diagnosed with septic arthritis of the left knee with Veillonella sp. growing from the joint aspirate on two successive cultures. The patient was treated with 6 weeks of oral metronidazole and 4 weeks of intravenous ceftriaxone in addition to arthroscopic drainage and irrigation. Rare causes of septic arthritis should be considered even in healthy adults with native joints. Closer follow-up might be needed to ensure successful treatment.

Feeding practice influences gut microbiome composition in very low birth weight preterm infants and the association with oxidative stress: A prospective cohort study.

Knowledge about the development of the preterm infant gut microbiota is emerging and is critical to their health. Very-low-birth-weight (VLBW; birth weight, <1500 g) infants usually have special dietary needs while showing increased oxidative stress related to intensive care. This prospective cohort study assessed the effect of feeding practice on gut microbiome development and oxidative stress in preterm infants. Fecal samples were collected from each infant in the early (1-2 weeks of enteral feeding) and late (2-4 weeks of enteral feeding) feeding stages. We performed high-throughput sequencing of V3-V4 regions of the 16S rRNA gene to analyze the fecal microbiome composition of 20 VLBW preterm infants and to determine the association of gut bacterial composition with feeding practice using an oxidative stress marker (urinary F2-isoprostane). Our results showed that feeding practices in the late stage significantly influenced the gut microbiome composition and oxidative stress in preterm infants. Preterm infants fed human milk + human milk fortifier and only formula diets showed a significant increase in F2-isoprostane levels (P < 0.05) compared with those fed human milk + formula diet. The gut microbiome of the infants fed the human milk + Human milk fortifier diet showed the lower relative abundance of Veillonella (P < 0.05) compared with that of the infants fed the human milk + formula diet. The gut microbiome of the infants fed the only formula diet showed the lowest microbial diversity and the highest relative abundance of Terrisporobacter (P < 0.05) compared with the gut microbiome of the infants fed the other diets. Correlation network analysis showed that urinary F2-isoprostane level was positively correlated with Terrisporobacter and Enterobacteriaceae abundance (P < 0.05) in the preterm infants. In conclusion, these data suggest that feeding practice affects the bacterial diversity and composition in the gut microbiome and is associated with oxidative stress in VLBW preterm infants.

Oral microbiomes in children with asthma and dental caries.

OBJECTIVE: Recently, a significant association between dental caries and the severity of bronchial asthma in children has been revealed. This finding indicates a possible relationship between the oral microbiome and the pathogenesis of asthma. The purpose of our study was to estimate differences in the dental plaque microbiota of asthmatic children with and without dental caries by 16S rDNA sequencing. MATERIAL AND METHODS: Dental plaque samples were obtained with a spoon excavator from the occlusal surface of one deciduous tooth (the second mandibular left molar in caries-free children and the most affected tooth in caries-affected children). Total DNA was extracted from dental plaque. DNA libraries were analysed by 16S rRNA gene sequencing on the MiSeq (Illumina) platform. RESULTS: There were no significant differences in the composition of bacterial communities from both caries-affected and caries-free children with asthma. The "caries-enriched" genus was Veillonella (Veillonellaceae, Selenomonadales, Negativicutes). Relative abundance of Neisseria was significantly higher in caries-free children with asthma (p < 0.05). CONCLUSIONS: The most significant difference in compared bacterial communities was a higher relative abundance of Veillonella in caries-affected plaques that suggests its involvement in pathogenesis of caries. Potential respiratory pathogens are present in oral cavity of both caries-affected and caries-free asthmatic children.

Breastfeeding: a key modulator of gut microbiota characteristics in late infancy.

The objective of this study was to investigate the impact of the most commonly cited factors that may have influenced infants' gut microbiota profiles at one year of age: mode of delivery, breastfeeding duration and antibiotic exposure. Barcoded V3/V4 amplicons of bacterial 16S-rRNA gene were prepared from the stool samples of 52 healthy 1-year-old Australian children and sequenced using the Illumina MiSeq platform. Following the quality checks, the data were processed using the Quantitative Insights Into Microbial Ecology pipeline and analysed using the Calypso package for microbiome data analysis. The stool microbiota profiles of children still breastfed were significantly different from that of children weaned earlier (P<0.05), independent of the age of solid food introduction. Among children still breastfed, Veillonella spp. abundance was higher. Children no longer breastfed possessed a more 'mature' microbiota, with notable increases of Firmicutes. The microbiota profiles of the children could not be differentiated by delivery mode or antibiotic exposure. Further analysis based on children's feeding patterns found children who were breastfed alongside solid food had significantly different microbiota profiles compared to that of children who were receiving both breastmilk and formula milk alongside solid food. This study provided evidence that breastfeeding continues to influence gut microbial community even at late infancy when these children are also consuming table foods. At this age, any impacts from mode of delivery or antibiotic exposure did not appear to be discernible imprints on the microbial community profiles of these healthy children.

Veillonella parvula spondylodiscitis.

OBJECTIVES: Veillonella parvula is an anaerobic Gram-negative coccus rarely involved in bone and joint infections. PATIENTS AND METHOD: We report the case of a Veillonella parvula vertebral osteomyelitis (VO) in a female patient without any risk factor. RESULTS: The 35-year-old patient was immunocompetent and presented with Veillonella parvula VO. She was admitted to hospital for inflammatory lower back pain. The discovertebral sample was positive for Veillonella parvula. Literature data on Veillonella VO is scarce. Reported cases usually occurred in immunocompromised patients. Diagnosis delay can be up to four months. Patients are usually afebrile. Outcome with antimicrobial treatment alone is favorable in half of cases. Other patients must undergo surgery. CONCLUSIONS: Veillonella VO may occur in immunocompetent patients and have a clinical spectrum of mechanical lower back pain.

HPV infection and bacterial microbiota in breast milk and infant oral mucosa.

OBJECTIVE: We investigated the association between bacterial microbiota in breast milk and the infant mouth. The influence of human papilloma virus (HPV) infection on infant oral microbiota was also assessed. MATERIAL AND METHODS: Altogether 35 breast milk and 35 infant oral samples with known HPV status were selected from the Finnish Family HPV Study cohort. In total, there were 31 mother-infant pairs. The microbiota composition was characterized by 16S rRNA gene sequencing (V3-V4 region). RESULTS: HPV DNA was present in 8.6% (3/35) of the breast milk and 40% (14/35) of the infant oral samples. Eight shared genera between breast milk and infant oral were found; these included Streptococcus, Staphylococcus, Unclassified Gemellaceae, Rothia, Veillonella, Haemophilus, Propionibacterium and Corynebacterium. HPV status was not associated with either microbiota richness or diversity in the infant mouth. However, the infant oral microbiota clustered in different groups according to HPV status. We detected higher abundance of Veillonella dispar (p = 0.048) at species level in HPV negative infant oral samples. We did not detect differences in the breast milk microbiota composition related to HPV infection due to only three HPV positive milk samples. CONCLUSIONS: HPV infection is associated with distinct oral bacterial microbiota composition in infants. The direction of causality underlying the phenomenon remains unclear.

Titanium as a modifier of the peri-implant microbiome structure.

BACKGROUND: Recent data support the implication of accelerated titanium dissolution products in peri-implantitis. It is unknown whether these dissolution products have an effect on the peri-implant microbiome, the target of existing peri-implantitis therapies. PURPOSE: This study assessed the relationship between the peri-implant microbiome, dissolved titanium levels, and peri-implantitis. MATERIALS AND METHODS: Clinical, microbiome, and titanium data were collected from a periodontal population having implants in function for 10 years. Clinical examinations were performed, and submucosal plaque samples were collected from the deepest site per implant. An aliquot of the sample was used for 16S rRNA gene sequencing, with the remainder analyzed for titanium quantity using mass spectrometry. Sequences were clustered into taxonomic units at 97% minimum sequence similarity using the QIIME pipeline approach. RESULTS: Fifteen implants were assessed. According to established case definitions, six had a diagnosis of peri-implantitis; nine were healthy. The genera Streptococcus, Prevotella and Haemophilus characterized peri-implant health. Peri-implantitis was associated with a marked increase in Veillonella. Quantities of dissolved titanium were identified in 40% of sites. Titanium presence was associated with peri-implant disease status (P = .02) and correlated to the first principal component of the microbiome (rho = 0.552) and its alpha-diversity (rho = -0.496). Canonical correlation analyses found that titanium levels, but not health or disease status of the implant, were significantly associated with the microbiota composition (P = .045). CONCLUSIONS: These findings suggest an association between titanium dissolution products and peri-implantitis and support a role for these products in modifying the peri-implant microbiome structure and diversity.