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Background Streptococcal toxic shock syndrome (STSS) is an acute, multisystem and toxin-mediated disease that usually causes shock and multiple organ failure in the early stages of its clinical course. It is associated with a substantial increase in mortality rate. The disease has been associated with invasive group A Streptococcus and is rarely caused by Streptococcus mitis (S. mitis). In healthy adults, S. mitis is closely related to endocarditis but rarely related to STSS. Case presentation We report a case of STSS caused by S. mitis in a healthy 45-year-old woman. She presented with fever 14 h after surgery and with hypotension 24 h later, and she subsequently suffered from septic shock, low albumin, dysfunction of coagulation, acute kidney dysfunction, respiratory alkalosis and metabolic acidosis, acute respiratory distress syndrome and cellulitis of the incision. The diagnosis was obtained through clinical manifestation and blood culture examination. The patient was treated with aggressive fluid resuscitation, adequate antibiotics for a total of 4 weeks, respiratory support, and surgical debridement and drainage of the incision. She was discharged after her vital signs returned to normal and the incision healed on day 40 after surgery. Conclusions The diagnosis of STSS is often delayed or missed, which leads to a high mortality rate. It is possible to cure patients if the disease can be identified early and treated with aggressive fluid resuscitation, adequate antibiotics and control of the source of infection. Clinicians should consider the disease in the differential diagnosis of septic shock to prevent death.

Objective To test the effect of antimicrobial photodynamic therapy (A-PDT) on the oral biofilm formed with early colonizing microorganisms, using the photosensitizer methylene blue coupled with β-cyclodextrin nanoparticles and red light sources laser or LED (λ =660 nm). Methods The groups were divided into (n = 3, in triplicate): C (negative control, 0.9 % NaCl), CX (positive control, 0.2 % chlorhexidine), P (Photosensitizer/Nanoparticle), L (Laser), LED (light-emitting diode), LP (Laser + Photosensitizer/Nanoparticle) and LEDP (LED + Photosensitizer/Nanoparticle). A multispecies biofilm composed ofS. gordonii, S. oralis, S. mitis, and S. sanguinis was grown in microplates containing BHI supplemented with 1% sucrose (w/v) for 24 h. Light irradiations were applied with a laser at 9 J for 90 s (320 J/cm2), or with LED, at 8.1 J for 90 s (8.1 J/cm2). The microbial reduction was assessed by counting viable biofilm microorganisms in selective culture media, before and after the treatments. Data normality was assessed by the Shapiro-Wilk test, and the results were submitted to Kruskal-Wallis analysis, followed by Dunn's test, with a significance level of 5%. Results The groups LP and LEDP were able to significantly reduce the biofilm microorganism counts by as much as 4 log10 times compared to the negative control group (p 0.05). Conclusion The A-PDT mediated by encapsulated β-cyclodextrin methylene blue irradiated by Laser or LED was effective in the microbial reduction of multispecies biofilm composed of early colonizing microorganisms.

Streptococcus pneumoniae causes over one million deaths from lower respiratory infections per annum worldwide. Although mortality is very high in Southeast Asian countries, molecular epidemiological information remains unavailable for some countries. In this study, we report, for the first time, the whole-genome sequences and genetic profiles of pneumococcal strains isolated in Myanmar. We isolated 60 streptococcal strains from 300 children with acute respiratory infection at Yangon Children’s Hospital in Myanmar. We obtained whole-genome sequences and identified the species, serotypes, sequence types, antimicrobial resistance (AMR) profiles, virulence factor profiles and pangenome structure using sequencing-based analysis. Average nucleotide identity analysis indicated that 58 strains were S. pneumoniae and the other 2 strains were Streptococcus mitis . The major serotype was 19F (11 strains), followed by 6E (6B genetic variant; 7 strains) and 15 other serotypes; 5 untypable strains were also detected. Multilocus sequence typing analysis revealed 39 different sequence types, including 11 novel ones. In addition, genetic profiling indicated that AMR genes and mutations spread among pneumococcal strains in Myanmar. A minimum inhibitory concentration assay indicated that several pneumococcal strains had acquired azithromycin and tetracycline resistance, whereas no strains were found to be resistant against levofloxacin and high-dose penicillin G. Phylogenetic and pangenome analysis showed various pneumococcal lineages and that the pneumococcal strains contain a rich and mobile gene pool, providing them with the ability to adapt to selective pressures. This molecular epidemiological information can help in tracking global infection and supporting AMR control in addition to public health interventions in Myanmar.

Lipoteichoic acid (LTA) is a Gram-positive bacterial cell surface polymer that participates in host-microbe interactions. It was previously reported that the major human pathogen Streptococcus pneumoniae and the closely related oral commensals S. mitis and S. oralis produce type IV LTAs. Herein, using liquid chromatography/mass spectrometry-based lipidomic analysis, we found that in addition to type IV LTA biosynthetic precursors, S. mitis, S. oralis, and S. pneumoniae also produce glycerophosphate (Gro-P)-linked dihexosyl (DH)-diacylglycerol (DAG), which is a biosynthetic precursor of type I LTA. cdsA and pgsA mutants produce DHDAG but lack (Gro-P)-DHDAG, indicating that the Gro-P moiety is derived from phosphatidylglycerol (PG), whose biosynthesis requires these genes. S. mitis, but not S. pneumoniae or S. oralis, encodes an ortholog of the PG-dependent type I LTA synthase, ltaS. By heterologous expression analyses, we confirmed that S. mitis ltaS confers poly(Gro-P) synthesis in both Escherichia coli and Staphylococcus aureus and that S. mitis ltaS can rescue the growth defect of an S. aureus ltaS mutant. However, we do not detect a poly(Gro-P) polymer in S. mitis using an anti-type I LTA antibody. Moreover, Gro-P-linked DHDAG is still synthesized by an S. mitis ltaS mutant, demonstrating that S. mitis LtaS does not catalyze Gro-P transfer to DHDAG. Finally, an S. mitis ltaS mutant has increased sensitivity to human serum, demonstrating that ltaS confers a beneficial but currently undefined function in S. mitis. Overall, our results demonstrate that S. mitis, S. pneumoniae, and S. oralis produce a Gro-P-linked glycolipid via a PG-dependent, ltaS-independent mechanism. IMPORTANCE The cell wall is a critical structural component of bacterial cells that confers important physiological functions. For pathogens, it is a site of host-pathogen interactions. In this work, we analyze the glycolipids synthesized by the mitis group streptococcal species, S. pneumoniae, S. oralis, and S. mitis. We find that all produce the glycolipid, glycerophosphate (Gro-P)-linked dihexosyl (DH)-diacylglycerol (DAG), which is a precursor for the cell wall polymer type I lipoteichoic acid in other bacteria. We investigate whether the known enzyme for type I LTA synthesis, LtaS, plays a role in synthesizing this molecule in S. mitis. Our results indicate that a novel mechanism is responsible. Our results are significant because they identify a novel feature of S. pneumoniae, S. oralis, and S. mitis glycolipid biology.

This study aimed to examine the surface characteristics of low shrinkage composites and adhesion of Streptococcus mutans and Streptococcus mitis to these materials. Control material (glass) and three low shrinkage composites (Charisma Diamond, Kalore GC, Beatiful II LS) were used. After polishing procedure was applied to composite specimens, surface roughness (SR), surface free energy (SFE), and contact angle measurements were performed. Surfaces of composite were analyzed using scanning electron microscope and energy-dispersive X-ray spectroscopy. After pellicle formation with artificial saliva, S. mutans and S. mitis biofilms were incubated in 5% CO2 for 24 h at 37 degrees C and were analyzed using confocal laser scanning microscopy. The lowest SR and highest SFE values were found in the control group. While the contact angle of control was statistically lower than composites, statistically difference was not found between composite groups. S. mutans adhesion of composites was significantly lower than control group, but there was no significant difference between composites. S. mitis adhesion of all groups was statistically similar. SR did not affect the S. mutans and S. mitis adhesion. Less adherence of S. mutans to low shrinkage composites was associated with low SFE and high contact angle values. Even though the highest SR was observed in the Charisma Diamond, no difference was found between the composites in terms of bacterial adhesion.

We report a case of a 42-year-old man who presented with acute epigastric and retrosternal chest pain and exertional dyspnoea, and was subsequently diagnosed with polyserositis secondary to post-Streptococcal mitis infection. A CT scan showed a large pericardial effusion requiring pericardiocentesis, small bilateral pleural effusions and small amount of ascites. Several serological tests were done, which were all found to be normal. Pericardial and pleural fluid aspirates revealed an exudate. Culture of the pleural fluid yielded growth of S. mitis and this was deemed the cause of the polyserositis, which is rare. The patient made a spontaneous recovery. He was started on colchicine by the cardiologists to help prevent pericardial fluid recurrence and this was continued for 3 months. A dental review confirmed the presence of dental caries, the possible source of infection. On follow-up, the patient remained well with no further relapses.

This study aimed to evaluate the feasibility of diagnosing periodontitis via the identification of 18 bacterial species in mouth-rinse samples. Patients (n = 110) who underwent dental examinations in the Department of Periodontology at the Veterans Health Service Medical Center between 2018 and 2019 were included. They were divided into healthy and periodontitis groups. The overall number of bacteria, and those of 18 specific bacteria, were determined via real-time polymerase chain reaction in 92 mouth-rinse samples. Differences between groups were evaluated through logistic regression after adjusting for sex, age, and smoking history. There was a significant difference in the prevalence (healthy vs. periodontitis group) of Aggregatibacter actinomycetemcomitans (2.9% vs. 13.5%), Treponema denticola (42.9% vs. 69.2%), and Prevotella nigrescens (80% vs. 2.7%). Levels of Treponema denticola, Prevotella nigrescens, and Streptococcus mitis were significantly associated with severe periodontitis. We demonstrated the feasibility of detecting periopathogenic bacteria in mouth-rinse samples obtained from patients with periodontitis. As we did not comprehensively assess all periopathogenic bacteria, further studies are required to assess the potential of oral-rinsing solutions to indicate oral infection risk and the need to improve oral hygiene, and to serve as a complementary method for periodontal disease diagnosis.

Streptococcus mitis Nm-65 is a human commensal streptococcal strain of the mitis group that was isolated from the tooth surface of a patient with Kawasaki disease. The complete genome sequence of Nm-65 was obtained by means of hybrid assembly, using two next-generation sequencing data sets. The final assembly size was 2,085,837 bp, with 2,039 coding sequences.

The use of Next Generation Sequencing (NGS) techniques has generated a wide variety of blood microbiome data. Due to the large variation in bacterial DNA profiles between studies and the likely high concentrations of cell-free bacterial DNA in the blood, it is still not clear how such microbiome data relates to viable microbiota. For these reasons much remains to be understood about the true nature of any possible healthy blood microbiota and of bacteraemic events associated with disease. The gut, reproductive tracts, skin, and oral cavity are all likely sources of blood-borne bacteria. Oral bacteria, especially those associated with periodontal diseases, are also commonly associated with cardiovascular diseases such as infective endocarditis, and also have been linked to rheumatoid arthritis and Alzheimer’s disease. Periodontal treatment, dental probing, and toothbrushing have been shown to cause transient bacteraemia and oral bacteria from the phyla Firmicutes (e.g. Streptococci) and Bacteroidetes (e.g. Porphyromonas) are found in cardiovascular lesions (CVD). Many studies of blood bacterial DNA content however, find Proteobacteria DNA to be the dominant microbiome component, suggesting a gut origin. Most studies of this type use total DNA extracted from either whole blood or blood fractions, such as buffy coat. Here, using a method that purifies DNA from intact bacterial cells only, we examined blood donated by those with active, severe periodontitis and periodontally healthy controls and show that 43–52% of bacterial species in blood are classified as oral. Firmicutes, consisting largely of members of the Streptococcus mitis group and Staphylococcus epidermidis, were predominant at 63.5% of all bacterial sequences detected in periodontal health and, little changed at 66.7% in periodontitis. Compared to studies using total DNA Proteobacteria were found here at relatively low levels in blood at 13.3% in periodontitis and 17.6% in health. This study reveals significant phylogenetic differences in blood bacterial population profiles when comparing periodontal health to periodontal disease cohorts.

Background: Pneumonia is a leading cause of death worldwide and is a major healthcare challenge for HIV-infected persons. Despite this, the etiology of pneumonia in this population remains poorly understood. Methods: We employed a combination of bulk RNA sequencing of bronchoalveolar lavage fluid and standard culture- and PCR-based diagnostics to survey the landscape of transcriptionally active respiratory pathogens in 217 Ugandan patients with HIV who were hospitalized for pneumonia. Findings: A microbiologic diagnosis was obtained in 211 (97.2%) of individuals, with at least one microorganism of established respiratory pathogenicity identified in 113 (52.1%) of patients, and a microbe of possible pathogenicity identified in 94 (47.9%) of patients. Mycobacterium tuberculosis (MTB) was the most commonly identified established pathogen in 35 (16.1%) of the patients and bacterial or viral co-infections were found in 13 (37.2%) of MTB-positive individuals. Streptococcus mitis, not previously reported as a cause of pneumonia in patients with HIV, was the most commonly identified bacterial organism (n=37, 17.1% of patients), and Hemophilus influenzae was the most commonly identified established bacterial pathogen (n=20, 9.2% of patients). Pneumocystis jirovecii, Hemophilus influenza, human rhinovirus, Streptococcus species and Veillonella species were more prevalent in patients with a CD4 T-cell count of

IntroductionElectronic cigarette (ECIG) use or vaping has become popular globally. While the question “Is vaping safer than smoking?” continues, it is becoming clearer that one of the most dangerous components of E-liquids are the flavorings. Since the oral cavity is the first anatomical site to be assaulted by ECIG aerosol, the aim of this study is to test the hypothesis that flavored ECIG aerosols or E-liquids pose a more detrimental effect on the growth of commensal oral streptococcal bacteria compared to flavorless aerosols or E-liquids.MethodsKirby Bauer assays and 24-h planktonic growth curves were used to compare the effects of flavorless vs. flavored (tobacco, menthol, cinnamon, strawberry and blueberry) ECIG-generated aerosols and E-liquids on the growth of four common strains of oral commensal bacteria (Streptococcus gordonii, Streptococcus intermedius, Streptococcus mitis and Streptococcus oralis).ResultsKirby Bauer assays revealed inhibition of growth for all bacteria tested when exposed to 100% menthol, cinnamon or strawberry flavors. In contrast, 5% flavor in E-liquid had no effect. When exposed to 100 puffs of ECIG-generated aerosol ± flavors (≈ 0.05% flavor in brain heart infusion media) or an equivalent amount of E-liquid ± flavors, twenty-four hour planktonic growth curves indicated no effect on growth for all streptococci tested. Subsequent twenty-four hour planktonic growth curves testing the effects of E-liquid ± flavors (0.0625, 0.125, 0.25, 0.3125, 0.625, and 1.25% flavor in brain heart infusion media) revealed dose-dependent inhibition of growth, particularly for menthol, cinnamon and strawberry), for all bacteria tested.ConclusionThese results support the hypothesis that flavored E-liquids are more detrimental to the growth of oral commensal bacteria than unflavored E-liquids. The streptococci tested in this study are early colonizers and part of the foundation of oral biofilms and dental plaque. Disturbances in the composition and growth of these primary colonizers is crucial to the development of a healthy dental plaque and host-bacteria interactions. E-liquids and their aerosols containing flavoring agents alter the growth of these bacteria. Such perturbations of pioneering oral communities pose a potential risk to the health of the oral cavity and, ultimately, health in general.

Objektives: This study aims to investigate the effects of different antiseptic mouthwash on microbiota around the mini-screw applied to patients undergoing fixed orthodontic treatment. Materials and methods: From patients who have been undergoing fixed orthodontic treatment and who have mini-screws in their mouth, a total of 38 patients were selected for the study consisting of 4 groups, each of which has 15 mini-screws. The patients were selected from the following groups: no use of mouthwash (Group 1), use of 0.12% Chlorhexidine gluconate-containing mouthwash (Group 2), use of Essential oils-containing mouthwash (Group 3) and use of 7.5% Povidone-iodine-containing mouthwash (Group 4). Plaque indices and gingival indices of the patients were measured at the beginning (T 0 ) and at their appointments three weeks later (T 1 ). In addition, biological samples were collected from the sulcus around the mini-screw with the help of sterile paper point. Results: The total number of microorganisms around the mini-screw in Group 2, Group 3 and Group 4 decreased significantly compared to Group 1. A significant decrease in Streptococcus oralis , Streptococcus mitis , Candida parapsilosis, total bacteria, plaque index and gingival index count was observed in T 1 compared to T 0. Conclusion: Antiseptic mouthwash in Group 2, Group 3 and Group 4 can be used to reduce the number of microbial microbiota around the mini-screw and to improve oral hygiene.

This case presents a patient with bacteremia of an unusual organism with a history of monoclonal gammopathy of undetermined significance (MGUS). MGUS is typically thought to be asymptomatic until potential progression of the disease. This case reports a patient with a history of MGUS who does not show disease progression, however, may be showing symptoms, such as immunodeficiency. This case displays bacteremia with Streptococcus mitis within a two-week period of an invasive procedure. Recent studies parallel this case by showing MGUS patients may have two times the risk of infections compared to the unaffected population. This report brings up the question of taking prophylactic measures for this patient population to prevent future complications.

Candida albicans is a commensal polymorphic and opportunistic fungus, which usually resides as a small community in the oral cavities of a majority of humans. The latter eco-system presents this yeast varied opportunities for mutualistic interactions with other cohabitant oral bacteria, that synergizes its persistence and pathogenicity. Collectively, these communities live within complex plaque biofilms which may adversely affect the oral health and increase the proclivity for oral candidiasis. The proteome of such oral biofilms with myriad interkingdom interactions are largely underexplored. Herein, we employed limma differential expression analysis, and cluster analysis to explore the proteomic interactions of C. albicans biofilms with nine different common oral bacterial species, Aggregatibacter actinomycetemcomitans, Actinomyces naeslundii, Fusobacterium nucleatum, Enterococcus faecalis, Porphyromonas gingivalis, Streptococcus mutants, Streptococcus sanguinis, Streptococcus mitis, and Streptococcus sobrinus. Interestingly, upon exposure of C. albicans biofilms to the foregoing heat-killed bacteria, the proteomes of the fungus associated with cellular respiration, translation, oxidoreductase activity, and ligase activity were significantly altered. Subsequent differential expression and cluster analysis revealed the subtle, yet significant alterations in the C. albicans proteome, particularly on exposure to bacteria with dissimilar cell morphologies, and Gram staining characteristics.

While extensive literature exists about the role of oral bacterial pathogens like Porphyromonas gingivalis and Fusobacterium nucleatum in oral squamous cell carcinoma (OSCC), the role of health-associated species has been largely unexplored. In this study, we assessed the effect of Streptococcus mitis, Rothia mucilaginosa, Neisseria flavescens, Haemophilus parainfluenzae, Lautropia mirabilis, and Veillonella parvula on proliferation and expression of marker genes (IL-6, TNF-α, MMP3, CD36, CCD1, and NANOG) in OSCC cell lines CAL27, SCC25, and SCC4. Porphyromonas gingivalis was included as a pathogenic control. Both bacterial lysates (3 concentrations) and live cells (3 MOIs) were tested. S. mitis, H. parainfluenzae, and N. flavescens resulted in substantial, dose-dependent reduction of proliferation, which was found to be mediated by H2O2 for the former and intracellular infection in the latter two species. However, only H. parainfluenzae showed differential antiproliferative effect against the cancer cell lines vs. the normal control (TIGKs). In the gene expression assays, the health-associated species mostly downregulated CD36, a gene that plays an important role in tumor growth and metastasis, while P. gingivalis upregulated it. IL6 and TNF expression, on the other hand, was upregulated by almost all species, particularly the Gram-negatives including P. gingivalis. The effect on other genes was less evident and varied significantly by cell line. This exploratory study is the first insight into how health-associated bacteria may interact with OSCC. Further studies to explore whether the observed effects may have implications for the prevention or treatment of oral cancer are warranted.

Complex polymicrobial biofilm communities are abundant in nature particularly in the human oral cavity where their composition and fitness can affect health. While the study of these communities during disease is essential and prevalent, little is known about interactions within the healthy plaque community. Here we describe interactions between two of the most abundant species in this healthy microbiome, Haemophilus parainfluenzae and Streptococcus mitis. We discovered that H. parainfluenzae typically exists adjacent to Mitis group streptococci in vivo with which it also positively correlated based on microbiome data. By comparing in vitro coculture data to ex vivo microscopy we revealed that this co-occurrence is density dependent and further influenced by H2O2 production. We discovered that H. parainfluenzae has a more redundant, multifactorial response to H2O2 than related organisms and that the integrity of this system enhances streptococcal fitness. We also show that Mitis group streptococci can act as an in vivo source of NAD for H. parainfluenzae and that streptococci in vitro evoke patterns of carbon utilization from H. parainfluenzae that are similar to those observed in vivo. Our findings describe mechanistic interactions between two of the most abundant and prevalent members of healthy supragingival plaque that contribute to their survival in vivo.

Objectives This study aims to investigate the effects of tea extracts on biofilm formation by oral streptococci and the potential mechanisms behind the effects. Design We examined the effects of five types of tea extracts (green, oolong, black, pu-erh and chrysanthemum tea) on cell surface hydrophobicity and auto-aggregation of three different streptococcal species (Streptococcus mutans, Streptococcus salivarius and Streptococcus mitis) and evaluated their biofilm formation on four disparate hard surfaces (glass, stainless steel, hydroxyapatite and titanium). The correlation between biofilm formation and the cellular properties were investigated in order to study the mechanisms by which the tea extracts affect biofilm formation. Results Results show that the tea extracts reduced cell surface hydrophobicity (by up to 57.9 %) and, in some cases, altered cellular auto-aggregation (by up to 12 %) and biofilm formation (by up to 2.61 log CFU cm−2). Specifically, oolong tea extract was found to enhance biofilm formation by increasing cellular auto-aggregation and pu-erh tea extract retarded biofilm formation by increasing auto-aggregation. Biofilm formation correlated well to cell surface hydrophobicity and auto-aggregation in combination, but not to either one alone as determined by multiple linear regression analysis. Conclusions Tea extracts have the ability to modulate streptococcal biofilm formation by altering cell surface hydrophobicity and cellular aggregation.

Cyclic di-adenosine monophosphate (c-di-AMP) has emerged as an important bacterial signaling molecule that functions both as an intracellular second messenger in bacterial cells and an extracellular ligand involved in bacteria-host cross-talk. In this study, we identify and characterize proteins involved in controlling the c-di-AMP concentration in the oral commensal and opportunistic pathogen Streptococcusmitis (S. mitis). We identified three known types of c-di-AMP turnover proteins in the genome of S. mitis CCUG31611: a CdaA-type diadenylate cyclase as well as GdpP-, and DhhP-type phosphodiesterases. Biochemical analyses of purified proteins demonstrated that CdaA synthesizes c-di-AMP from ATP whereas both phosphodiesterases can utilize c-di-AMP as well as the intermediary metabolite of c-di-AMP hydrolysis 5&prime, phosphadenylyl-adenosine (pApA) as substrate to generate AMP, albeit at different catalytic efficiency. Using deletion mutants of each of the genes encoding c-di-AMP turnover proteins, we show by high resolution MS/MS that the intracellular concentration of c-di-AMP is increased in deletion mutants of the phosphodiesterases and non-detectable in the cdaA-mutant. We also detected pApA in mutants of the DhhP-type phosphodiesterase. Low and high levels of c-di-AMP were associated with longer and shorter chains of S. mitis, respectively indicating a role in regulation of cell division. The deletion mutant of the DhhP-type phosphodiesterase displayed slow growth and reduced rate of glucose metabolism.

Viridans group streptococci (VGS), especially the Streptococcus mitis-oralis subgroup, are pivotal pathogens in a variety of invasive endovascular infections, including &ldquo, toxic shock&rdquo, in neutropenic cancer patients and infective endocarditis (IE). Previously, we showed that the serial in vitro passage of S. mitis-oralis strains in sublethal daptomycin (DAP) resulted in rapid, high-level and stable DAP-resistance (DAP-R), which is accompanied by distinct changes in several genotypic and phenotypic signatures: (1) the disappearance of two key membrane phospholipids, phosphatidylglycerol (PG) and cardiolipin (CL), (2) increased membrane fluidity, (3) increased positive surface charge, (4) single nucleotide polymorphisms (SNPs) in two loci involved in CL biosynthesis (pgsA, cdsA), and (5) DAP hyperaccumulation. The current study examined these same metrics following in vitro serial DAP passages of a separate well-characterized S. mitis-oralis bloodstream isolate (SF100). Although some metrics seen in prior DAP post-passage strains were recapitulated with SF100 (e.g., pgsA SNPs, enhanced membrane fluidity), we observed the following major differences (comparing the parental versus post-passage variant): (1) no change in PG content, (2) reduced, but not absent, CL, with enhancement in phosphatidic acid (PA) content, (3) an unusual pattern of CL localization, (4) significantly decreased positive surface charge, (5) no difference in DAP accumulation, and (6) no cdsA SNPs. Thus, S. mitis-oralis strains are not &ldquo, pre-programmed&rdquo, phenotypically and/or genotypically to adapt in an identical manner during the evolution of the DAP-R.

Objectives: This study aims to investigate the effects of various mouthwashes on bacteremia development following a debonding process, which is performed after orthodontic treatment. Subjects and Methods: The study included patients who received fixed orthodontic treatment and were indicated for debonding. A total of 40 patients in four groups were selected for the study; no mouthwash (Group 1), mouthwash containing 0.12% chlorhexidine‑gluconate (Group 2), mouthwash containing essential‑oils (Group 3), and mouthwash containing 7.5% povidone‑iodine (Group 4). Before (T0) and following (T1) the debonding procedure, blood samples were obtained from the patients. Then, the blood samples were placed in blood culture bottles to investigate bacterial growth. Results: Based on the results of the study, it was determined that the blood samples obtained at T0 did not indicate any bacterial growth. Furthermore, it was observed that the blood samples obtained at T1 included Streptococcus viridans, Streptococcus oralis, Streptococcus mutans, and Staphylococcus aereus growth, respectively, in 4 patients from Group 1 while Streptococcus salivarius growth was observed in 1 patient from Group 3 in addition to Streptococcus mitis growth in 1 patient from Group 4. No bacterial growth was observed in Group 2. While the results obtained between Group 1 and Group 2 were statistically significant, no statistically significant difference was observed between other groups. Conclusions: Finally, it was determined that the mouthwash 0.12% chlorhexidine‑gluconate was statistically significant in comparison to the control group. It can be concluded that this mouthwash can be used to decrease bacterial density in oral flora before debonding procedures. Keywords: Bacteremia, bacterial endocarditis, chlorhexidine gluconate, debonding, mouthwashes

Background Viridans group streptococci of the Streptococcus mitis-oralis subgroup are important endovascular pathogens. They can rapidly develop high-level and durable non-susceptibility to daptomycin both in vitro and in vivo upon exposure to daptomycin. Two consistent genetic adaptations associated with this phenotype (i.e., mutations in cdsA and pgsA) lead to the depletion of the phospholipids, phosphatidylglycerol and cardiolipin, from the bacterial membrane. Such alterations in phospholipid biosynthesis will modify carbon flow and change the bacterial metabolic status. To determine the metabolic differences between daptomycin-susceptible and non-susceptible bacteria, the physiology and metabolomes of S. mitis-oralis strains 351 (daptomycin-susceptible) and 351-D10 (daptomycin non-susceptible) were analyzed. S. mitis-oralis strain 351-D10 was made daptomycin non-susceptible through serial passage in the presence of daptomycin. Results Daptomycin non-susceptible S. mitis-oralis had significant alterations in glucose catabolism and a re-balancing of the redox status through amino acid biosynthesis relative to daptomycin susceptible S. mitis-oralis. These changes were accompanied by a reduced capacity to generate biomass, creating a fitness cost in exchange for daptomycin non-susceptibility. Conclusions S. mitis-oralis metabolism is altered in daptomycin non-susceptible bacteria relative to the daptomycin susceptible parent strain. As demonstrated in Staphylococcus aureus, inhibiting the metabolic changes that facilitate the transition from a daptomycin susceptible state to a non-susceptible one, inhibits daptomycin non-susceptibility. By preventing these metabolic adaptations in S. mitis-oralis, it should be possible to deter the formation of daptomycin non-susceptibility.

Streptococcus mitis (S. mitis) is a commensal bacterial species that commonly colonizes the oropharynx and gastrointestinal tract. It is seldom reported as a human pathogen. However, immunocompromised individuals may be at risk of infection. We describe a 62-year-old male with prostate cancer who presented with multiple S. mitis abscesses masquerading as metastases. In addition, we discuss the differential diagnosis and treatment options for this rare opportunistic infection.

The Mitis group of streptococci includes an important human pathogen, Streptococcus pneumoniae (pneumococcus) and about 20 other related species with much lower pathogenicity. In clinical practice, some representatives of these species, especially Streptococcus pseudopneumoniae and Streptococcus mitis, are sometimes mistaken for S. pneumoniae based on the results of classical microbiological methods, such as optochin susceptibility and bile solubility. Several various molecular approaches that address the issue of correct identification of pneumococci and other Mitis streptococci have been proposed and are discussed in this review, including PCR- and gene sequencing-based tests as well as new developments in the genomic field that represents an important advance in our understanding of relationships within the Mitis group.

The aim of our study was to investigate phenotypic and genotypic features of streptococci misidentified (misID) asStreptococcus pneumoniae, obtained over 20 years from hospital patients in Poland. Sixty-three isolates demonstrating microbiological features typical for pneumococci (optochin susceptibility and/or bile solubility) were investigated by phenotypic tests,lytAand 16S rRNA gene polymorphism and whole-genome sequencing (WGS). All isolates had a 6-bp deletion in thelytA3′ terminus, characteristic for Mitis streptococc and all but two isolates lacked the pneumococcal signature cytosine at nucleotide position 203 in the 16S rRNA genes. The counterparts ofpsaAandplywere present in 100% and 81.0% of isolates, respectively; the spn9802 and spn9828 loci were characteristic for 49.2% and 38.1% of isolates, respectively. Phylogenetic trees and networks, based on the multilocus sequence analysis (MLSA) scheme, ribosomal multilocus sequence typing (rMLST) scheme and core-genome analysis, clearly separated investigated isolates fromS. pneumoniaeand demonstrated the polyclonal character of misID streptococci, associated with theStreptococcus pseudopneumoniaeandStreptococcus mitisgroups. While theS. pseudopneumoniaeclade was relatively well defined in all three analyses, only the core-genome analysis revealed the presence of another cluster comprising a fraction of misID streptococci and a strain proposed elsewhere as a representative of a novel species in the Mitis group. Our findings point to complex phylogenetic and taxonomic relationships amongS. mitis-like bacteria and support the notion that this group may in fact consist of several distinct species.

The objective of this study was to determine if the interaction between common oral commensal bacteria and oral epithelial cells would provide protective effects against the invasion of periodontopathogen Porphyromonas gingivalis. Oral epithelial OKF6/Tert cells were used in co-cultures with Streptococcus gordonii, Streptococcus oralis, Streptococcus mitis, and Streptococcus intermedius. The viability of OKF6/Tert cells following a bacterial challenge was evaluated by trypan blue exclusion. The adherence of commensal species was determined by CFU counts. P. gingivalis invasion in OKF6/Tert cells was assessed before and after exposure to commensal species according to CFU counts. Viability assays show that only S. gordonii and S. intermedius display low toxicity toward OKF6/Tert cells. Both commensals adhere to OKF6/Tert cells at an average ratio of 1 CFU to 10 cells. P. gingivalis invasion into host cells is significantly reduced by 25% or 60% after exposure to S. gordonii or S. intermedius, respectively. The results suggest that these commensal species bind to host cells and diminish P. gingivalis invasion. This is important in the context of periodontal disease since P. gingivalis primarily acts on the host by invading it. Therefore, efforts to decrease invasion will eventually lead to future therapies harnessing the mechanisms employed by oral commensal bacteria.

This study aimed to investigate the effects of an oral health optimized diet on the composition of the supragingival oral plaque in a randomized controlled trial. Participants of the standard diet group (n = 5) had a diet high in processed carbohydrates and did not change their dietary behavior during the observation. The healthy diet group (n = 9) had to change the diet after 2 weeks from a diet high in processed carbohydrates to a diet low in carbohydrates, rich in omega‐3 fatty acids, rich in vitamins C and D, antioxidants and fiber for 4 weeks. Saliva and supragingival plaque samples were taken at the end of week two and eight of the observation period to investigate the composition of microbiota in saliva and supragingival plaque. Data were subjected to an exploratory analysis to identify significant differences. Statistically significant differences were only found in the healthy diet group between the baseline (week 2) and the final sample (week 8) for specific species in plaque and saliva samples. A reduction of the total counts of Streptococcus mitis group, Granulicatella adiacens, Actinomyces spp., and Fusobacterium spp. was found in plaque samples of the healthy diet group. In saliva samples of the healthy diet group, the total counts of Actinomyces spp. and Capnocytophaga spp. decreased. A diet low in carbohydrates, rich in omega‐3 fatty acids, rich in vitamins C and D, and rich in fiber reduced Streptococcus mitis group, Granulicatella adiacens, Actinomyces spp., and Fusobacterium spp. in the supragingival plaque., This study aimed to investigate the effects of an oral health optimized diet on the composition of the supragingival oral plaque in a randomized controlled trial. A diet low in carbohydrates, rich in omega‐3 fatty acids, rich in vitamins C and D, and rich in fiber induces significantly lower counts of caries‐ and periodontitis‐associated pathogens and thus, a favorable shift in the bacterial.

Streptococcus mitis is an alpha-hemolytic species of Streptococcus and is the most prevalent organism of the oral flora. In patients with dental procedures or trauma and underlying damaged heart valves, it can cause infection of the valves (endocarditis). It has a propensity to affect the left-sided heart valves (mitral and aortic valves) in non-intravenous drug users (IVDU), whereas right-sided heart valves (tricuspid and pulmonic valves) in IVDU. We describe a case of a patient who presented with mitral valve endocarditis that was treated with antibiotics. He was lost to follow-up and then presented four years after his index presentation in cardiogenic shock from severe streptococcal mitis endocarditis causing severe mitral regurgitation. His course deteriorated to the point where the patient required a valve replacement surgery under hemodynamic support.

Streptococcus mitis is a member of the mitis group of the genus Streptococcus, which includes commensal species of the oral cavity and upper respiratory tract. Here, we report 39 complete genome sequences of S. mitis strains isolated from the oral cavity and urogenital tract of a woman and her male sexual partner., Microbiology Resource Announcements, 9 (1), ISSN:2576-098X

Differentiation between mitis group streptococci (MGS) bacteria in routine laboratory tests has become important for obtaining accurate epidemiological information on the characteristics of MGS and understanding their clinical significance. The most reliable method of MGS species identification is multilocus sequence analysis (MLSA) with seven house-keeping genes; however, because this method is time-consuming, it is deemed unsuitable for use in most clinical laboratories. In this study, we established a scheme for identifying 12 species of MGS (S. pneumoniae, S. pseudopneumoniae, S. mitis, S. oralis, S. peroris, S. infantis, S. australis, S. parasanguinis, S. sinensis, S. sanguinis, S. gordonii, and S. cristatus) using the MinION nanopore sequencer (Oxford Nanopore Technologies, Oxford, UK) with the taxonomic aligner "What's in My Pot?" (WIMP; Oxford Nanopore's cloud-based analysis platform) and Kraken2 pipeline with the custom database adjusted for MGS species identification. The identities of the species in reference genomes (n = 514), clinical isolates (n = 31), and reference strains (n = 4) were confirmed via MLSA. The nanopore simulation reads were generated from reference genomes, and the optimal cut-off values for MGS species identification were determined. For 31 clinical isolates (S. pneumoniae = 8, S. mitis = 17 and S. oralis = 6) and 4 reference strains (S. pneumoniae = 1, S. mitis = 1, S. oralis = 1, and S. pseudopneumoniae = 1), a sequence library was constructed via a Rapid Barcoding Sequencing Kit for multiplex and real-time MinION sequencing. The optimal cut-off values for the identification of MGS species for analysis by WIMP and Kraken2 pipeline were determined. The workflow using Kraken2 pipeline with a custom database identified all 12 species of MGS, and WIMP identified 8 MGS bacteria except S. infantis, S. australis, S. peroris, and S. sinensis. The results obtained by MinION with WIMP and Kraken2 pipeline were consistent with the MGS species identified by MLSA analysis. The practical advantage of whole genome analysis using the MinION nanopore sequencer is that it can aid in MGS surveillance. We concluded that MinION sequencing with the taxonomic aligner enables accurate MGS species identification and could contribute to further epidemiological surveys.

Background: Invasive infections with non-beta-haemolytic streptococci (NBHS) is quite common and presents the clinicians with difficulties regarding which patients are at risk for infective endocarditis (IE). The HANDOC score was developed to identify patients with NBHS bacteraemia who are at low risk of IE. This study was conducted to validate HANDOC in an external cohort. Methods: Patients with NBHS in blood cultures between March and September 2016 in a Danish centre were included as part of an on-going study. Patient characteristics were collected to classify bacteria according to Dukés criteria and the components of the HANDOC score were collected retrospectively from the patients’ medical records. Results: 68 patients were included in the cohort, of which 16 fulfilled Dukés criteria for IE. All patients with IE (16 of 16) had a HANDOC score above the predefined cut-off. Cases of IE were found in patients with. Streptococcus mitis, Streptococcus bovis, Streptococcus mutans, Streptococcus anginosus, and Streptococcus sanguinis group streptococci. The HANDOC score thus had a sensitivity of 100% and a specificity of 62% in this cohort. Conclusions: HANDOC has a sensitivity of 100% and a relatively high specificity (62%) also in a prospectively enrolled cohort of patients from another country than its origin. This indicates that HANDOC can be implemented in clinical practice to identify patients with a low risk of IE in whom echocardiography can be omitted.

Tese de mestrado em Biologia Molecular e Genética, Universidade de Lisboa, Faculdade de Ciências, 2021 Submitted by Cristina Manessiez (camanessiez@fc.ul.pt) on 2021-05-10T15:08:04Z No. of bitstreams: 1 ulfc126231_tm_João_Borralho.pdf: 41799 bytes, checksum: f139a6b02e7753a40b6102d0d6e44b97 (MD5) Made available in DSpace on 2021-05-10T15:08:29Z (GMT). No. of bitstreams: 1 ulfc126231_tm_João_Borralho.pdf: 41799 bytes, checksum: f139a6b02e7753a40b6102d0d6e44b97 (MD5) Previous issue date: 2021

Objective The objective was to determine the antibiofilm efficacy of Cymbopogon martinii and Thymus zygis essential oils and to estimate the disruption potential of oil-based endodontic irrigants on the multispecies biofilm formed in the root canals of extracted teeth. Design The essential oils were characterized (GC–MS), while their antibacterial and cytotoxic properties were detected by microdilution and MTT assays. Particles sizes and polydispersity indices were determined for the irrigants. The isolates from root canals of pediatric patients were identified (MALDI-TOF). The multispecies biofilms were formed from Streptococcus mitis, Streptococcus sanguinis and Enterococcus faecalis. Antibiofilm properties of the essential oils and irrigants were determined by crystal violet and plate counting assay. Statistical analysis was performed by one-way ANOVA. Results The screening of biofilm biomass revealed a disruption potential of C. martinii essential oil. The plate counting assay showed the efficacy of both oils in diminishing cell viability: high in biofilms (reduction of log10CFU was 2.75–2.87) and moderate in the planktons formed above. The essential oil-based irrigants showed the same antibiofilm activity as in the control (1.5 % sodium hypochlorite) for C. martini and almost 2-fold higher for T. zygis. Successive irrigations with 1.5 % sodium hypochlorite, saline and an oil-based irrigant was more efficient for C. martini than for the control (reductions of log10CFU was 1.69 and 1.14, respectively). Conclusions Notable activities achieved by essential oils and oil-based irrigants, particularly regarding C. martini, against the biofilm consisting of S. mitis, S. sanguinis, and E. faecalis, are expected to encourage further research in endodontics.

Objective: To perform an in vitro analysis of antibacterial and antifungal potential of an alcoholic extract from the leaves of Guapira Graciliflora Mart. against oral microorganisms and determine its chemical composition. Material and Methods: A hydroalcoholic extract of the leaves form G. graciliflora was obtained through maceration, vacuum concentration and freeze-drying. Antibacterial and antifungal activities were evaluated against Streptococcus mutans , Streptococcus salivarius , Streptococcus oralis , Streptococcus parasanguinis , Streptococcus mitis and strains of Candida albicans using broth microdilution method. Phytochemical analysis determined the total phenolic compounds, protein concentration and total of sugars present in the extract . Results: G. Graciliflora demonstrated antifungal activity against the LM 11 and LM 410 clinical isolates of C. albicans (MIC 0.5 mg/mL and 2 mg/mL, respectively). The other microorganisms tested were resistant to the extract. The phytochemical analysis revealed 3% proteins, 13% total sugars and 17% phenolic compounds . Conclusion: G. Graciliflora has antifungal activity against clinical strains of C. albicans and exhibits proteins, sugars and phenolic compounds in its chemical composition.

Background/purposeTo date, studies examining polymicrobial infections in ocular disease have mostly been limited to keratitis or endophthalmitis. We characterized polybacterial infections compared to monobacterial infections in prior clinical studies evaluating besifloxacin ophthalmic suspension 0.6% for the treatment of bacterial conjunctivitis and report on associated microbiological outcomes.MethodsIn this post-hoc analysis, microbiological data for subjects with conjunctivitis due to one or more than one bacterial species in three previous studies (two vehicle-, one active-controlled) of besifloxacin were extracted. Bacterial species identified at baseline were deemed causative if their colony count equaled or exceeded species-specific prespecified threshold criteria. In subjects with polybacterial infections, the fold-increase over threshold was used to rank order the contribution of individual species. Baseline pathogens and their minimum inhibitory concentrations (MICs) for common ophthalmic antibiotics were compared by infection type, as were microbial eradication rates following treatment with besifloxacin.ResultsOf 1041 subjects with culture-confirmed conjunctivitis, 17% had polybacterial and 83% had monobacterial conjunctivitis at baseline. In polybacterial compared to monobacterial infections, Haemophilus influenzae and Streptococcus pneumoniae were identified less frequently as the dominant infecting species (P = 0.042 and PConclusionsApproximately one in five subjects with bacterial conjunctivitis are infected with more than one bacterial species underscoring the need for a broad-spectrum antibiotic for such infections. Besifloxacin treatment resulted in robust eradication rates of these infections comparable to monobacterial infections.Trial registrationNCT000622908, NCT00347932, NCT00348348.

Fixed orthodontic appliances hinder the maintenance of proper oral hygiene and result in dental plaque accumulation. Many studies report that qualitative changes in the dental flora occur after initiating the orthodontic treatment, but there is a paucity of literature on the same topic among Moroccan orthodontic patients. The aim of this study was to evaluate the changes of the oral microbial flora during the orthodontic treatment period of a young Moroccan population. Materials and Methods. Dental plaque samples of 18 patients, who were randomly selected before the placement of orthodontic appliances, were collected to isolate and identify the bacterial species involved using classical bacteriological methods for species’ culture and identification. The reading was recorded at T0 before placement of the device. New samples were taken again one month later and then three months afterwards, where the readings were recorded as T1 and T2, respectively. The culture was made via Columbia Agar with 5% sheep blood, Todd Hewitt Broth, and Schaedler medium containing vitamin K3. Bacterial species were identified using API-20 Strep for Streptococci and API-20 A for anaerobic bacteria. The phoenix system was used for identification. Results. After three months of orthodontic treatment, the increase in the frequency of Streptococcus sobrinus and Streptococcus mitis were significant (0.01 and 0.02, respectively) as well as for Lactobacillus (0.03). No significant difference was recorded for other bacterial species. Conclusion. There is a significant qualitative change in oral microorganisms after three months of orthodontic treatment, especially for bacteria that are incriminated in caries formation.

The essential oils of Eugenia uniflora L. (EuEO), Plinia cauliflora (Mart.) (PcEO) and Syzygium cumini (L.) (ScEO), of the Myrtaceae family, were analyzed in gas chromatography with mass spectrometry in order to identify their volatile components, as well as their in vitro leishmanicidal, antibacterial and cytotoxic activities. A total of 34 compounds were identified from EuEO. The major compounds found in EuEO were germacrone (8.52%), spathulenol (8.20%), α-selinene (7.50%) and (Z)-β-elemenone (4.88%). PcEO contained 52 compounds, with the major compounds being (E)-cariophene (14.69%), β-bisabolene (9.36%), (E, E)-α-farnecene (8.07%) and globulol (7.86%). ScEO contained 38 compounds, with the major compounds being α-pinene (21.20%), globulol (15.30%), eugenol (11.20%), and α-terpineol (8.88%). Our results demonstrated that EuEO, PcEO and ScEO, tested against Leishmania amazonensis, affected promastigote growth in a dose-dependent manner. The IC50 of EuEO, PcEO and ScEO were 0.99, 0.46 and 8.78 μg/mL, respectively, while the IC50 of Amphotericin B was 0.60 μg/mL. All the EO of the species evaluated presented moderate inhibitory activity, with Minimum Inhibitory Concentration (MIC) variation of 100 to 400 μg/mL for the following bacteria tested: Streptococcus mutans, Streptococcus mitis, Streptococcus sanguinis, Streptococcus sobrinus, Streptococcus salivarius, Actinomyces naeslundii, Bacteroides fragilis, Bacteroides thetaiotaomicron, Prevotella nigrescens and Porphyromonas gingivalis. Our results showed that the IC50 values for the treated tumor cell lines ranged from 76.5 to 106.2 μg/mL for EuEO and 76.6 to 116.2 μg/mL for PcEO. ScEO was not tested on the tumor cell lines because it presented an IC50 > 400 μg/mL on normal cell lines. These results highlight the variability of the chemical composition of essential oils and the high potential of their bactericidal and leishmanicidal activities.

Made available in DSpace on 2019-10-06T16:51:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The aim was to evaluate in vitro possible interactions, gene expression, and biofilm formation in species of Candida albicans, Streptococcus mitis, and Streptococcus sanguinis and their in vivo pathogenicity. The in vitro analysis evaluated the effects of S. mitis and S. sanguinis on C. albicans’s biofilm formation by CFU count, filamentation capacity, and adhesion (ALS1, ALS3, HWP1) and transcriptional regulatory gene (BCR1, CPH1, EFG1) expression. In vivo studies evaluated the pathogenicity of the interaction of the microorganisms on Galleria mellonella, with analyses of the CFU per milliliter count and filamentation. In vitro results indicated that there was an observed decrease in CFU (79.4–71.5%) in multi-species biofilms. The interaction with S. mitis inhibited filamentation, which seems to increase its virulence factor with over-expression of genes ALS1, ALS3, and HWP1 as well the interaction with S. sanguinis as ALS3 and HWP1. S. mitis upregulated BRC1, CPH1, and EFG1. The histological images of in vivo study indicate an increase in the filamentation of C. albicans when in interaction with the other species. It was concluded that S. mitis interaction suggests increased virulence factors of C. albicans, with periods of lower virulence and proto-cooperation in the interaction with S. sanguinis. Institute of Science and Technology Department of Biosciences and Oral Diagnosis UNESP – Univ Estadual Paulista, Francisco José Longo 777, São Dimas Institute of Science and Technology Department of Biosciences and Oral Diagnosis UNESP – Univ Estadual Paulista, Francisco José Longo 777, São Dimas

In common with many bacterial pathogens, Streptococcus pneumoniae has a polysaccharide capsule which facilitates immune evasion and determines virulence. Recent data have shown that the closely related Streptococcus mitis also expresses polysaccharide capsules including those with an identical chemical structure to S. pneumoniae capsular serotypes. We utilized atomic force microscopy (AFM) techniques to investigate the biophysical properties of S. mitis and S. pneumoniae strains expressing the same capsular serotypes that might relate to differences in virulence potential. When comparing S. mitis and S. pneumoniae strains with identical capsule serotypes, S. mitis strains were susceptible to neutrophil killing, and electron microscopy and AFM demonstrated significant morphological differences. Force-volume mapping using AFM showed distinct force-curve profiles for the center and edge areas of encapsulated streptococcal strains. This "edge effect" was not observed in unencapsulated bacteria and therefore was a direct representation of the mechanical properties of the bacterial capsule. When two strains of S. mitis and S. pneumoniae expressed an identical capsular serotype, they presented similar biomechanical characteristics. This infers a potential relationship between capsule biochemistry and nanomechanics, independent of bacterial strain. Overall, this study demonstrates that it is possible to investigate reproducibly the mechanistic, structural, and mechanical properties of both the capsule and the body of individual living bacterial cells and relate the data to virulence phenotypes. We have demonstrated that using nanomechanics to investigate individual bacterial cells we can now begin to identify the surface properties bacterial pathogens require to avoid host-mediated immunity.

Streptococci from the mitis group (represented mainly by Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii) form robust biofilms with Candida albicans in different experimental models. These microorganisms have been found in polymicrobial biofilms forming on titanium biomaterial surfaces in humans with peri-implant disease. The purpose of this work was to study mutualistic interactions in biofilms forming on titanium and their effect on the adjacent mucosa, using a relevant infection model. Single and mixed biofilms of C. albicans and each Streptococcus species were grown on titanium disks. Bacterial and fungal biovolume and biomass were quantified in these biofilms. Organotypic mucosal constructs were exposed to preformed titanium surface biofilms to test their effect on secretion of proinflammatory cytokines and cell damage. C. albicans promoted bacterial biofilms of all mitis Streptococcus species on titanium surfaces. This relationship was mutualistic since all bacterial species upregulated the efg1 hypha-associated gene in C. albicans. Mixed biofilms caused increased tissue damage but did not increase proinflammatory cytokine responses compared to biofilms comprising Candida alone. Interestingly, spent culture medium from tissues exposed to titanium biofilms suppressed Candida growth on titanium surfaces. IMPORTANCE Our findings provide new insights into the cross-kingdom interaction between C. albicans and Streptococcus species representative of the mitis group. These microorganisms colonize titanium-based dental implant materials, but little is known about their ability to cause inflammation and damage of the adjacent mucosal tissues. Using an in vitro biomaterial-mucosal interface infection model, we showed that mixed biofilms of each species with C. albicans enhance tissue damage. One possible mechanism for this effect is the increased fungal hypha-associated virulence gene expression we observed in mixed biofilms with these species. Interestingly, we also found that the interaction of multispecies biofilms with organotypic mucosal surfaces led to the release of growth-suppressing mediators of Candida, which may represent a homeostatic defense mechanism of the oral mucosa against fungal overgrowth. Thus, our findings provide novel insights into biofilms on biomaterials that may play an important role in the pathogenesis of mucosal infections around titanium implants.

N. meningitidis is transmitted from person to person by aerosol droplets produced by breathing, talking, or coughing or by direct contact with a contaminated fluid. The natural reservoir of N. meningitidis is the human nasopharynx mucosa, located at the back of the nose and above the oropharynx. The means by which meningococci cross the nasopharyngeal wall is still under debate, due to the lack of a convenient and relevant model mimicking the nasopharyngeal niche. Here, we took advantage of Calu-3 cells grown in air interface culture to study how meningococci colonize the nasopharyngeal niche. We report that the airway mucus is both a niche for meningococcal growth and a protective barrier against N. meningitidis infection. As such, N. meningitidis behaves like commensal bacteria and is unlikely to induce infection without an external trigger., Neisseria meningitidis is an inhabitant of the nasopharynx, from which it is transmitted from person to person or disseminates in blood and becomes a harmful pathogen. In this work, we addressed colonization of the nasopharyngeal niche by focusing on the interplay between meningococci and the airway mucus that lines the mucosa of the host. Using Calu-3 cells grown in air interface culture (cells grown with the apical domain facing air), we studied meningococcal colonization of the mucus and the host response. Our results suggested that N. meningitidis behaved like commensal bacteria in mucus, without interacting with human cells or actively transmigrating through the cell layer. As a result, type IV pili do not play a role in this model, and meningococci did not trigger a strong innate immune response from the Calu-3 cells. Finally, we have shown that this model is suitable for studying interaction of N. meningitidis with other bacteria living in the nasopharynx and that Streptococcus mitis, but not Moraxella catarrhalis, can promote meningococcal growth in this model. IMPORTANCE N. meningitidis is transmitted from person to person by aerosol droplets produced by breathing, talking, or coughing or by direct contact with a contaminated fluid. The natural reservoir of N. meningitidis is the human nasopharynx mucosa, located at the back of the nose and above the oropharynx. The means by which meningococci cross the nasopharyngeal wall is still under debate, due to the lack of a convenient and relevant model mimicking the nasopharyngeal niche. Here, we took advantage of Calu-3 cells grown in air interface culture to study how meningococci colonize the nasopharyngeal niche. We report that the airway mucus is both a niche for meningococcal growth and a protective barrier against N. meningitidis infection. As such, N. meningitidis behaves like commensal bacteria and is unlikely to induce infection without an external trigger.

The work presented by Audry et al. (M. Audry, C. Robbe-Masselot, J.-P. Barnier, B. Gachet, et al., mSphere 4:e00494-19, 2019, https://doi.org/10.1128/mSphere.00494-19) gives new insight into the interactions of Neisseria meningitidis and the human nasopharynx., The work presented by Audry et al. (M. Audry, C. Robbe-Masselot, J.-P. Barnier, B. Gachet, et al., mSphere 4:e00494-19, 2019, https://doi.org/10.1128/mSphere.00494-19) gives new insight into the interactions of Neisseria meningitidis and the human nasopharynx. Using an air interface tissue culture model of a polarized, mucus-secreting epithelium, Audry et al. demonstrate that N. meningitidis bacteria do not commonly invade epithelial cells. Rather, they are trapped in the mucus layer, where they are protected from dessication. In this model, meningicocci fail to elicit a pro-inflammatory immune response and show growth effects in response to another nasopharyngeal colonizer, Streptococcus mitis. These findings prompt new questions about pathobiont behaviors, the role of mucus in bacterium-host interactions, and modeling human infection.

Objective To find antagonistic strains in the respiratory tract having bacteriostatic properties against common pathogens. Methods The oropharyngeal microbiota of five healthy children aged 4–6 years were collected and α‐hemolytic bacteria screened on 15% sheep blood agar. Bacteriostatic effects of the isolated α‐hemolytic bacteria on Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes were evaluated by the Oxford cup method. Antagonistic strains were identified by mass spectrometry, and the16S rDNAs were sequenced, and their best bacteriostatic concentrations and antagonistic spectra for Klebsiella pneumoniae, Proteus vulgaris, Enterobacter cloacae, Acinetobacter Baumanii, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes were evaluated. Results Of 300 isolated α‐hemolytic bacterial clones, four exhibited bacteriostatic activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes. Mass spectrometric analyses revealed that two of them were Streptococcus mitis and two others were Streptococcus parasanguinis strains. Further tests showed that all 4 antagonistic strains also had bacteriostatic effects on Klebsiella pneumoniae, Proteus vulgaris, Enterobacter cloacae, and Acinetobacter Baumanii, and the mode of action was not mediated by lactic acid production. Conclusion Four antagonistic Streptococcus strains derived from oropharyngeal microbiotas showed bacteriostatic effects on pathogens and may be involved in pharyngeal microbiome homeostasis., In the present study, we screened 300 bacterial strains from the oropharyngeal microbiota of five healthy children and found four antagonistic Streptococcus strains, which exhibited broad‐spectrum antagonistic activities for Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Enterobacter cloacae and Acinetobacter baumanii. We suggest, that the growth of this Streptococcus strains may prevent pathogenic bacterial expansion.

Aim To determine if bacteria associated with persistent apical periodontitis induce species-specific pro-inflammatory cytokine responses in macrophages, and the effects of this species-specific microenvironment on osteogenic differentiation. Methodology Macrophages were exposed to Enterococcus faecalis, Streptococcus oralis, Streptococcus mitis, Fusobacterium nucleatum, Treponema denticola or Tannerella forsythia, and levels of TNF-α and IL-1β elicited were determined by immunoassay. Following treatment of MG-63 pre-osteoblasts with conditioned media from bacteria-exposed macrophages, osteogenic differentiation and viability of osteoblasts were analyzed by Alizarin Red Staining and MTS assay, respectively. Statistical analysis was carried out by one-way anova with the Tukey post-hoc test. Differences were considered to be significant if P Results Macrophages exposed to Gram-positive bacteria did not produce significant amounts of cytokines. F. nucleatum-challenged macrophages produced up to four-fold more TNF-α and IL-1β compared to T. denticola or T. forsythia. Only conditioned media from macrophages treated with Gram-negative bacteria decreased mineralization and viability of osteoblasts. Conclusions Gram-positive bacteria did not impact osteogenic differentiation and appeared innocuous. Gram-negative bacteria, in particular F. nucleatum elicited an enhanced pro-inflammatory response in macrophages, inhibited osteogenic differentiation and reduced cell viability. The findings suggest that the presence of this organism could potentially increase the severity of persistent apical periodontitis.