SARS-CoV-2 and Prevotella spp.: friend or foe? A systematic literature review.

During this global pandemic of the COVID-19 disease, a lot of information has arisen in the media and online without scientific validation, and among these is the possibility that this disease could be aggravated by a secondary bacterial infection such as Prevotella, as well as the interest or not in using azithromycin, a potentially active antimicrobial agent. The aim of this study was to carry out a systematic literature review, to prove or disprove these allegations by scientific arguments. The search included Medline, PubMed, and Pubtator Central databases for English-language articles published 1999-2021. After removing duplicates, a total of final eligible studies (n=149) were selected. There were more articles showing an increase of Prevotella abundance in the presence of viral infection like that related to Human Immunodeficiency Virus (HIV), Papillomavirus (HPV), Herpesviridae and respiratory virus, highlighting differences according to methodologies and patient groups. The arguments for or against the use of azithromycin are stated in light of the results of the literature, showing the role of intercurrent factors, such as age, drug consumption, the presence of cancer or periodontal diseases. However, clinical trials are lacking to prove the direct link between the presence of Prevotella spp. and a worsening of COVID-19, mainly those using azithromycin alone in this indication.

Periodontal pathogens and clinical parameters in chronic periodontitis.

The use of next generation sequencing and bioinformatics has revealed the complexity and richness of the human oral microbiota. While some species are well known for their periodontal pathogenicity, the molecular-based approaches for bacterial identification have raised awareness about new putative periodontal pathogens. Although they are found increased in case of periodontitis, there is currently a lack of data on their interrelationship with the periodontal measures. We processed the sequencing data of the subgingival microbiota of 75 patients with hemochromatosis and chronic periodontitis in order to characterize the well-described and newly identified subgingival periodontal pathogens. We used correlation tests and statistical models to assess the association between the periodontal pathogens and mean pocket depth, and to determine the most relevant bacterial biomarkers of periodontitis severity. Based on correlation test results, nine taxa were selected and included in the statistical models. The multiple linear regression models adjusted for systemic and periodontal clinical variables showed that mean pocket depth was negatively associated with Aggregatibacter and Rothia, and positively associated with Porphyromonas. Furthermore, a bacterial ratio that was previously described as a signature of dysbiosis in periodontitis (%Porphyromonas+%Treponema+%Tannerella)/(%Rothia+%Corynebacterium) was the most significant predictor. In this specific population, we found that the best model in predicting the mean pocket depth was microbial dysbiosis using the dysbiosis ratio taxa formula. While further studies are needed to assess the validity of these results on the general population, such a dysbiosis ratio could be used in the future to monitor the subgingival microbiota.

Increased transferrin saturation is associated with subgingival microbiota dysbiosis and severe periodontitis in genetic haemochromatosis.

Genetic haemochromatosis (GH) is responsible for iron overload. Increased transferrin saturation (TSAT) has been associated with severe periodontitis, which is a chronic inflammatory disease affecting tissues surrounding the teeth and is related to dysbiosis of the subgingival microbiota. Because iron is essential for bacterial pathogens, alterations in iron homeostasis can drive dysbiosis. To unravel the relationships between serum iron biomarkers and the subgingival microbiota, we analysed samples from 66 GH patients. The co-occurrence analysis of the microbiota showed very different patterns according to TSAT. Healthy and periopathogenic bacterial clusters were found to compete in patients with normal TSAT (≤45%). However, significant correlations were found between TSAT and the proportions of Porphyromonas and Treponema, which are two genera that contain well-known periopathogenic species. In patients with high TSAT, the bacterial clusters exhibited no mutual exclusion. Increased iron bioavailability worsened periodontitis and promoted periopathogenic bacteria, such as Treponema. The radical changes in host-bacteria relationships and bacterial co-occurrence patterns according to the TSAT level also suggested a shift in the bacterial iron supply from transferrin to NTBI when TSAT exceeded 45%. Taken together, these results indicate that iron bioavailability in biological fluids is part of the equilibrium between the host and its microbiota.

Periodontal status and serum biomarker levels in HFE haemochromatosis patients. A case-series study.

AIM: To investigate the association between periodontal status and serum biomarkers in patients with HFE haemochromatosis. MATERIAL AND METHODS: This clinical case series included 84 HFE-C282Y homozygous patients. Periodontal evaluation was performed using clinical attachment level, probing depth, gingival bleeding index, visible plaque index and gingival index. Serum markers of iron metabolism were collected from medical records. The relationship between serum biomarkers of iron burden and the severity of periodontitis was investigated. RESULTS: The study population consisted of 47 men and 37 women, routinely treated in the Unit of Hepatology, University Hospital, Rennes. All patients presented with periodontitis (mild: n = 1, moderate: n = 37 and severe: n = 46). There was a positive association between transferrin saturation >45% and the severity of periodontitis (adjusted odds ratio = 5.49, p = .002). CONCLUSION: Severe periodontitis is associated with the severity of iron burden in patients with HFE-related hereditary haemochromatosis. Dental examination should be included in the initial assessment of all these patients.

Signature of Microbial Dysbiosis in Periodontitis.

Periodontitis is driven by disproportionate host inflammatory immune responses induced by an imbalance in the composition of oral bacteria; this instigates microbial dysbiosis, along with failed resolution of the chronic destructive inflammation. The objectives of this study were to identify microbial signatures for health and chronic periodontitis at the genus level and to propose a model of dysbiosis, including the calculation of bacterial ratios. Published sequencing data obtained from several different studies (196 subgingival samples from patients with chronic periodontitis and 422 subgingival samples from healthy subjects) were pooled and subjected to a new microbiota analysis using the same Visualization and Analysis of Microbial Population Structures (VAMPS) pipeline, to identify microbiota specific to health and disease. Microbiota were visualized using CoNet and Cytoscape. Dysbiosis ratios, defined as the percentage of genera associated with disease relative to the percentage of genera associated with health, were calculated to distinguish disease from health. Correlations between the proposed dysbiosis ratio and the periodontal pocket depth were tested with a different set of data obtained from a recent study, to confirm the relevance of the ratio as a potential indicator of dysbiosis. Beta diversity showed significant clustering of periodontitis-associated microbiota, at the genus level, according to the clinical status and independent of the methods used. Specific genera (Veillonella, Neisseria, Rothia, Corynebacterium, and Actinomyces) were highly prevalent (>95%) in health, while other genera (Eubacterium, Campylobacter, Treponema, and Tannerella) were associated with chronic periodontitis. The calculation of dysbiosis ratios based on the relative abundance of the genera found in health versus periodontitis was tested. Nonperiodontitis samples were significantly identifiable by low ratios, compared to chronic periodontitis samples. When applied to a subgingival sample set with well-defined clinical data, the method showed a strong correlation between the dysbiosis ratio, as well as a simplified ratio (Porphyromonas, Treponema, and Tannerella to Rothia and Corynebacterium), and pocket depth. Microbial analysis of chronic periodontitis can be correlated with the pocket depth through specific signatures for microbial dysbiosis.IMPORTANCE Defining microbiota typical of oral health or chronic periodontitis is difficult. The evaluation of periodontal disease is currently based on probing of the periodontal pocket. However, the status of pockets "on the mend" or sulci at risk of periodontitis cannot be addressed solely through pocket depth measurements or current microbiological tests available for practitioners. Thus, a more specific microbiological measure of dysbiosis could help in future diagnoses of periodontitis. In this work, data from different studies were pooled, to improve the accuracy of the results. However, analysis of multiple species from different studies intensified the bacterial network and complicated the search for reproducible microbial signatures. Despite the use of different methods in each study, investigation of the microbiota at the genus level showed that some genera were prevalent (up to 95% of the samples) in health or disease, allowing the calculation of bacterial ratios (i.e., dysbiosis ratios). The correlation between the proposed ratios and the periodontal pocket depth was tested, which confirmed the link between dysbiosis ratios and the severity of the disease. The results of this work are promising, but longitudinal studies will be required to improve the ratios and to define the microbial signatures of the disease, which will allow monitoring of periodontal pocket recovery and, conceivably, determination of the potential risk of periodontitis among healthy patients.

Periodontitis induced by Porphyromonas gingivalis drives periodontal microbiota dysbiosis and insulin resistance via an impaired adaptive immune response.

OBJECTIVE: To identify a causal mechanism responsible for the enhancement of insulin resistance and hyperglycaemia following periodontitis in mice fed a fat-enriched diet. DESIGN: We set-up a unique animal model of periodontitis in C57Bl/6 female mice by infecting the periodontal tissue with specific and alive pathogens like Porphyromonas gingivalis (Pg), Fusobacterium nucleatum and Prevotella intermedia. The mice were then fed with a diabetogenic/non-obesogenic fat-enriched diet for up to 3 months. Alveolar bone loss, periodontal microbiota dysbiosis and features of glucose metabolism were quantified. Eventually, adoptive transfer of cervical (regional) and systemic immune cells was performed to demonstrate the causal role of the cervical immune system. RESULTS: Periodontitis induced a periodontal microbiota dysbiosis without mainly affecting gut microbiota. The disease concomitantly impacted on the regional and systemic immune response impairing glucose metabolism. The transfer of cervical lymph-node cells from infected mice to naive recipients guarded against periodontitis-aggravated metabolic disease. A treatment with inactivated Pg prior to the periodontal infection induced specific antibodies against Pg and protected the mouse from periodontitis-induced dysmetabolism. Finally, a 1-month subcutaneous chronic infusion of low rates of lipopolysaccharides from Pg mimicked the impact of periodontitis on immune and metabolic parameters. CONCLUSIONS: We identified that insulin resistance in the high-fat fed mouse is enhanced by pathogen-induced periodontitis. This is caused by an adaptive immune response specifically directed against pathogens and associated with a periodontal dysbiosis.

Hypermutator Salmonella Heidelberg induces an early cell death in epithelial cells.

We have previously described that a strain of Salmonella Heidelberg with a hypermutator phenotype, B182, adhered strongly to HeLa cells. In this work, we showed that this hypermutator Salmonella strain invaded HeLa epithelial cells and induced cytoskeleton alteration. Those changes lead to HeLa cell death which was characteristic of apoptosis. For the first time, we showed that this hypermutator strain induced apoptosis associated with the activation of caspases 2, 9 and 3. Complementation of B182 strain showed a decrease in cells death induction. In the presence of other Salmonella Heidelberg with a normomutator phenotype, such as WT and SL486, cell death and caspase 3 were undetectable. These results suggested that early apoptosis and caspase 3 activation were specific to B182. Besides, B182 induced LDH release and caspase 3 activation in CaCo-2 and HCT116 cells. Heat-treated B182 and diffusible products failed to induce this phenotype. Epithelial cells treatment with cytochalasin D caused the inhibition of B182 internalisation and caspase 3 activation. These results showed that this cell death required active S. Heidelberg B182 protein synthesis and bacterial internalisation. However sipB and sopB, usually involved in apoptosis induced by Salmonella were not overexpressed in B182, contrary to fimA and fliC. Comparative genome analysis showed numerous mutations as in rpoS which would be more investigated. The role of the hypermutator phenotype might be suspected to be implicated in these specific features. This result expands our knowledge about strong mutators frequently found in bacterial organisms isolated from clinical specimens.

Association of Anti-Porphyromonas gingivalis Antibody Titers With Nonsmoking Status in Early Rheumatoid Arthritis: Results From the Prospective French Cohort of Patients With Early Rheumatoid Arthritis.

OBJECTIVE: To investigate the possible link between Porphyromonas gingivalis infection and rheumatoid arthritis (RA), according to antibody profile, genetic and environmental factors, and RA severity. METHODS: For assessing P gingivalis infection, serum levels of antibodies directed against P gingivalis lipopolysaccharide were measured in 694 patients with early RA who were not exposed to steroids or disease-modifying antirheumatic drugs. Anti-P gingivalis antibody titers were compared between patients with early RA and various control groups, and according to various patient characteristics. RESULTS: Anti-P gingivalis antibody titers did not significantly differ between patients with RA and controls and did not significantly differ with anti-citrullinated protein antibody (ACPA), rheumatoid factor (RF), or HLA shared epitope status. Anti-P gingivalis antibody titers were significantly higher among patients who had never smoked compared to patients who had ever smoked (P = 0.0049). Among nonsmokers, high anti-P gingivalis antibody levels were associated with a higher prevalence of erosive change (47.5% versus 33.3% with modified Sharp/van der Heijde score erosion subscale ≥1; P = 0.0135). CONCLUSION: In this large early RA cohort, we did not detect any association of anti-P gingivalis antibodies with RA or with ACPA status. These results suggest that the association of periodontitis and RA could be linked to bacterial species other than P gingivalis or to a mechanism other than citrullination. Nevertheless, we found higher anti-P gingivalis antibody titers in nonsmokers. In addition, in this population of nonsmokers, high anti-P gingivalis antibody titers were associated with more severe disease. We hypothesize that the role of tobacco in RA pathogenesis is so high that the effect of P gingivalis could be revealed only in a population not exposed to tobacco.

Is biofilm formation related to the hypermutator phenotype in clinical Enterobacteriaceae isolates?

In bacteria, complex adaptive processes are involved during transition from the planktonic to the biofilm mode of growth, and mutator strains are more prone to producing biofilms. Enterobacteriaceae species were isolated from urinary tract infections (UTIs; 222 strains) and from bloodstream infections (BSIs; 213 strains). Relationship between the hypermutable phenotype and biofilm forming capacity was investigated in these clinical strains. Mutation frequencies were estimated by monitoring the capacity of each strain to generate mutations that conferred rifampicin resistance on supplemented medium. Initiation of biofilm formation was assayed by determining the ability of the cells to adhere to a 96-well polystyrene microtitre plate. UTI Enterobacteriaceae strains showed significantly higher biofilm-forming capacity: 63.1% (54.0% for E. coli strains) vs. 42.3% for BSI strains (47.7% for E. coli). Strains isolated from UTIs did not present higher mutation frequencies than those from BSIs: contrary to what has been widely described for P. aeruginosa strains, isolated from pulmonary samples in patients suffering from cystic fibrosis, no relationship was found between the hypermutator phenotype in Enterobacteriaceae and the ability to initiate a biofilm.

Molecular mechanisms of higher MICs of antibiotics and quaternary ammonium compounds for Escherichia coli isolated from bacteraemia.

OBJECTIVES: A previous study identified an association between high MICs of quaternary ammonium compounds (QACs) and antibiotic resistance. The current aim was to investigate the genetic background of this association. METHODS: Of 153 Escherichia coli clinical strains, seven were selected for their low or high MICs of antibiotics and/or QACs. Integron resistance gene contents were identified by sequencing after PCR amplification. The genes encoding the efflux pump AcrA/TolC and its regulatory regions marA, marO, marR, soxS and rob were sequenced. The gene expression of acrA, tolC, marA, marOR, soxS and rob was assessed by quantitative real-time PCR. MICs in the presence and absence of the efflux pump inhibitor phenyl-arginine-ß-naphthylamide (PAßN) were compared. RESULTS: Of the seven strains, five were resistant to amoxicillin, amoxicillin/clavulanic acid and/or co-trimoxazole (trimethoprim/sulfamethoxazole) and/or had high MICs of ciprofloxacin and QACs. Four of the five harboured a class 1 integron (intI1). In three of these four strains, the presence of dfrA/sul1 and qacEΔ1 gene cassettes correlated with resistance to co-trimoxazole and high MICs of QACs. In all of the five strains, overexpression of tolC, marOR and soxS was always associated with higher MICs of antibiotics and/or QACs. PAßN reduced the MICs of ciprofloxacin and QACs, suggesting that extrusion of ciprofloxacin and QACs from bacteria depends on the AcrAB-TolC system. CONCLUSIONS: To our knowledge, this report is the first to describe dual involvement of the AcrAB-TolC system and class 1 integrons in clinical E. coli strains.

Impact of a mutator phenotype on motility and cell adherence in Salmonella Heidelberg.

In this study, we investigated adherence and motility of the hypermutator Salmonella enterica Heidelberg B182 bovine strain related to a 12bp deletion in mutS. This mutator phenotype was associated with increased adherence to epithelial cells and with high expression of fimA as shown by real-time RT-PCR. Motility studies showed that fliC were up-regulated in the B182 strain, while fljA and fljB were down-regulated. In order to determine if mutated mutS is implicated in this genes expression, isogenic strains, derived from a WT strain, containing the 12bp deletion in mutS (Δ12bpmutS) or an inactivated mutS (ΔmutS) were generated. Δ12bpmutS and ΔmutS strains showed a spontaneous mutation rate similar to the environmental strain B182, but exhibited lower adherence capacity and fimA expression. In contrast to the fimbriae genes, in Δ12bpmutS, fliC expression was up-regulated, but fljA and fljB expression were decreased, as in the B182 strain. Only fljB expression was increased in ΔmutS mutants. Taken together, our data suggest that mutS alteration does not influence fimbriae expression but can impact flagella genes.

Bacterial hypermutation: clinical implications.

Heritable hypermutation in bacteria is mainly due to alterations in the methyl-directed mismatch repair (MMR) system. MMR-deficient strains have been described from several bacterial species, and all of the strains exhibit increased mutation frequency and recombination, which are important mechanisms for acquired drug resistance in bacteria. Antibiotics select for drug-resistant strains and refine resistance determinants on plasmids, thus stimulating DNA recombination via the MMR system. Antibiotics can also act as indirect promoters of antibiotic resistance by inducing the SOS system and certain error-prone DNA polymerases. These alterations have clinical consequences in that efficacious treatment of bacterial infections requires high doses of antibiotics and/or a combination of different classes of antimicrobial agents. There are currently few new drugs with low endogenous resistance potential, and the development of such drugs merits further research.