Publications by authors named "Bob T Rosier"

5 Publications

  • Page 1 of 1

A Single Dose of Nitrate Increases Resilience Against Acidification Derived From Sugar Fermentation by the Oral Microbiome.

Front Cell Infect Microbiol 2021 3;11:692883. Epub 2021 Jun 3.

Department of Health and Genomics, Center for Advanced Research in Public Health, FISABIO Foundation, Valencia, Spain.

Tooth decay starts with enamel demineralization due to an acidic pH, which arises from sugar fermentation by acidogenic oral bacteria. Previous work has demonstrated that nitrate limits acidification when incubating complex oral communities with sugar for short periods (e.g., 1-5 h), driven by changes in the microbiota metabolism and/or composition. To test whether a single dose of nitrate can reduce acidification derived from sugar fermentation , 12 individuals received a nitrate-rich beetroot supplement, which was compared to a placebo in a blinded crossover setting. Sucrose-rinses were performed at baseline and 2 h after supplement or placebo intake, and the salivary pH, nitrate, nitrite, ammonium and lactate were measured. After nitrate supplement intake, the sucrose-induced salivary pH drop was attenuated when compared with the placebo (p < 0.05). Salivary nitrate negatively correlated with lactate production and positively with ΔpH after sucrose exposure (r= -0.508 and 0.436, respectively, both p < 0.05). Two additional pilot studies were performed to test the effect of sucrose rinses 1 h (n = 6) and 4 h (n = 6) after nitrate supplement intake. In the 4 h study, nitrate intake was compared with water intake and bacterial profiles were analysed using 16S rRNA gene Illumina sequencing and qPCR detection of . Sucrose rinses caused a significant pH drop (p < 0.05), except 1 h and 4 h after nitrate supplement intake. After 4 h of nitrate intake, there was less lactate produced compared to water intake (p < 0.05) and one genus; , increased in abundance. This small but significant increase was confirmed by qPCR (p < 0.05). The relative abundance of and negatively correlated with lactate production (r = -0.601 and -0.669, respectively) and positively correlated with pH following sucrose intake (r = 0.669, all p < 0.05). Together, these results show that nitrate can acutely limit acidification when sugars are fermented, which appears to result from lactate usage by nitrate-reducing bacteria. Future studies should assess the longitudinal impact of daily nitrate-rich vegetable or supplement intake on dental health.
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http://dx.doi.org/10.3389/fcimb.2021.692883DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8238012PMC
July 2021

The Subgingival Plaque Microbiome, Systemic Antibodies Against Bacteria and Citrullinated Proteins Following Periodontal Therapy.

Pathogens 2021 Feb 10;10(2). Epub 2021 Feb 10.

Oral Sciences, College of Medical, Veterinary and Life Sciences, Dental School, University of Glasgow, Glasgow G12 8QQ, UK.

Periodontitis (PD) shows an association with rheumatoid arthritis (RA) and systemic inflammation. Periodontal pathogens, namely and , are proposed to be capable of inducing citrullination of peptides in the gingiva, inducing the formation of anti-citrullinated protein antibodies (ACPAs) within susceptible hosts. Here, we sought to investigate whether periodontal treatment influenced systemic inflammation and antibody titres to , , and ACPA in 42 systemically health patients with periodontal disease. Subgingival plaque and serum samples were collected from study participants before (baseline) and 90 days after treatment to analyse the abundance of specific bacteria and evaluate anti-bacterial antibodies, C-reactive protein (CRP), tumour necrosis factor α (TNF-α), interleukin 6 (IL-6) and ACPA in serum. Following treatment, all patients showed reduced periodontal inflammation. Despite observing a weak positive correlation between CRP and IL-6 with periodontal inflammation at baseline, we observed no significant reductions in any indicators of systemic inflammation 90 days after treatment. In contrast, anti- IgG significantly reduced post-treatment ( < 0.001, Wilcoxon signed rank test), although no changes were observed for other antibody titres. Patients who had detectable in subgingival plaques had significantly higher anti- IgG and ACPA titres, suggesting a potential association between colonisation and systemic antibody titres.
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http://dx.doi.org/10.3390/pathogens10020193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7916579PMC
February 2021

Isolation and Characterization of Nitrate-Reducing Bacteria as Potential Probiotics for Oral and Systemic Health.

Front Microbiol 2020 15;11:555465. Epub 2020 Sep 15.

Department of Health and Genomics, Center for Advanced Research in Public Health, FISABIO Foundation, Valencia, Spain.

Recent evidence indicates that the reduction of salivary nitrate by oral bacteria can contribute to prevent oral diseases, as well as increase systemic nitric oxide levels that can improve conditions such as hypertension and diabetes. The objective of the current manuscript was to isolate nitrate-reducing bacteria from the oral cavity of healthy donors and test their probiotic potential to increase the nitrate-reduction capacity (NRC) of oral communities. Sixty-two isolates were obtained from five different donors of which 53 were confirmed to be nitrate-reducers. Ten isolates were selected based on high NRC as well as high growth rates and low acidogenicity, all being species. The genomes of these ten isolates confirmed the presence of nitrate- and nitrite reductase genes, as well as lactate utilization genes, and the absence of antimicrobial resistance, mobile genetic elements and virulence genes. The pH at which most nitrate was reduced differed between strains. However, acidic pH 6 always stimulated the reduction of nitrite compared to neutral pH 7 or slightly alkaline pH 7.5 ( < 0.01). We tested the effect of six out of 10 isolates on oral biofilm development in the presence or absence of 6.5 mM nitrate. The integration of the isolates into communities was confirmed by Illumina sequencing. The NRC of the bacterial communities increased when adding the isolates compared to controls without isolates ( < 0.05). When adding nitrate (prebiotic treatment) or isolates in combination with nitrate (symbiotic treatment), a smaller decrease in pH derived from sugar metabolism was observed ( < 0.05), which for some symbiotic combinations appeared to be due to lactate consumption. Interestingly, there was a strong correlation between the NRC of oral communities and ammonia production even in the absence of nitrate ( = 0.814, < 0.01), which indicates that bacteria involved in these processes are related. As observed in our study, individuals differ in their NRC. Thus, some may have direct benefits from nitrate as a prebiotic as their microbiota naturally reduces significant amounts, while others may benefit more from a symbiotic combination (nitrate + nitrate-reducing probiotic). Future clinical studies should test the effects of these treatments on oral and systemic health.
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http://dx.doi.org/10.3389/fmicb.2020.555465DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522554PMC
September 2020

Dose-Response Analysis of Chemotactic Signaling Response in Salmonella typhimurium LT2 upon Exposure to Cysteine/Cystine Redox Pair.

PLoS One 2016 7;11(4):e0152815. Epub 2016 Apr 7.

FOM Institute for Atomic and Molecular Physics (AMOLF), Amsterdam, The Netherlands.

The chemotaxis system enables motile bacteria to search for an optimum level of environmental factors. Salmonella typhimurium senses the amino acid cysteine as an attractant and its oxidized dimeric form, cystine, as a repellent. We investigated the dose-response dependence of changes in chemotactic signaling activity upon exposure to cysteine and cystine of S. typhimurium LT2 using in vivo fluorescence resonance energy transfer (FRET) measurements. The dose-response curve of the attractant response to cysteine had a sigmoidal shape, typical for receptor-ligand interactions. However, in a knockout strain of the chemoreceptor genes tsr and tar, we detected a repellent response to cysteine solutions, scaling linearly with the logarithm of the cysteine concentration. Interestingly, the magnitude of the repellent response to cystine also showed linear dependence to the logarithm of the cystine concentration. This linear dependence was observed over more than four orders of magnitude, where detection started at nanomolar concentrations. Notably, low concentrations of another oxidized compound, benzoquinone, triggered similar responses. In contrast to S. typhimurium 14028, where no response to cystine was observed in a knockout strain of chemoreceptor genes mcpB and mcpC, here we showed that McpB/McpC-independent responses to cystine existed in the strain S. typhimurium LT2 even at nanomolar concentrations. Additionally, knocking out mcpB and mcpC did not affect the linear dose-response dependence, whereas enhanced responses were only observed to solutions that where not pH neutral (>100 μM cystine) in the case of McpC overexpression. We discuss that the linear dependence of the response on the logarithm of cystine concentrations could be a result of a McpB/C-independent redox-sensing pathway that exists in S. typhimurium LT2. We supported this hypothesis with experiments with defined cysteine/cystine mixed solutions, where a transition from repellent to attractant response occurred depending on the estimated redox potential.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0152815PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4824473PMC
August 2016

Historical and contemporary hypotheses on the development of oral diseases: are we there yet?

Front Cell Infect Microbiol 2014 16;4:92. Epub 2014 Jul 16.

Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Free University Amsterdam Amsterdam, Netherlands.

Dental plaque is an oral biofilm that much like the rest of our microbiome has a role in health and disease. Specifically, it is the cause of very common oral diseases such as caries, gingivitis, and periodontitis. The ideas about oral disease development have evolved over time. In the nineteenth century, scientists could not identify bacteria related to disease due to the lack of technology. This led to the "Non-Specific Plaque Hypothesis" or the idea that the accumulation of dental plaque was responsible for oral disease without discriminating between the levels of virulence of bacteria. In the twentieth century this idea evolved with the techniques to analyze the changes from health to disease. The first common hypothesis was the "Specific Plaque Hypothesis" (1976) proposing that only a few species of the total microflora are actively involved in disease. Secondly, the "Non-Specific Plaque Hypothesis" was updated (1986) and the idea that the overall activity of the total microflora could lead to disease, was enriched by taking into account difference in virulence among bacteria. Then, a hypothesis was considered that combines key concepts of the earlier two hypotheses: the "Ecological Plaque Hypothesis" (1994), which proposes that disease is the result of an imbalance in the microflora by ecological stress resulting in an enrichment of certain disease-related micro-organisms. Finally, the recent "Keystone-Pathogen Hypothesis" (2012) proposes that certain low-abundance microbial pathogens can cause inflammatory disease by interfering with the host immune system and remodeling the microbiota. In this comprehensive review, we describe how these different hypotheses, and the ideas around them, arose and test their current applicability to the understanding of the development of oral disease. Finally, we conclude that an all-encompassing ecological hypothesis explaining the shifts from health to disease is still lacking.
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http://dx.doi.org/10.3389/fcimb.2014.00092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4100321PMC
March 2015
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