Strains Of Oral Streptococci Research Articles

Antibacterial and Antibiofilm Effects of L-Carnitine-Fumarate on Oral Streptococcal Strains Streptococcus mutans and Streptococcus sobrinus.

Streptococcus mutans is a major pathogenic habitant of oral caries. Owing to its physiological and biochemical features, it prevails in the form of plaque biofilm together with another important mutans streptococci species, Streptococcus sobrinus. Both species are considered as initiators of cavity lesions, and biofilm is essential to the dental caries process. Compared with the planktonic populations, the biofilm form has higher resistance to environmental conditions and antibiotics. Dental plaques also secure the long-term survival of microorganisms and protection from any stress conditions. To address the need for new antibiofilm agents, we have focused on L-carnitine-fumarate, a fumarate-conjugated quaternary ammonium compound. Using the macro-broth susceptibility testing method, we established its MIC value as 6.0 mg/mL. The MBC value, determined from the broth dilution minimum inhibitory concentration test by sub-culturing it to BHI agar plates, was established as 7.0 mg/mL. Antibiofilm efficacy was tested in 96-well plates coated with saliva using BHI broth supplemented with 1% sucrose as a standard approach. The obtained results allowed us to assess the MIBC as 7.5 mg/mL and the MBBC value as 10.0 mg/mL. The latter concentration also caused approximately 20% eradication of pre-existing biofilm. EPS-rich matrix, forming the core of the biofilm and enabling a confined acidic microenvironment, was also examined and confirmed the effectiveness of 10.0 mg/mL L-carnitine-fumarate concentration in inhibiting EPS formation. Furthermore, the anti-adherent and anti-aciduric impacts of L-carnitine-fumarate were investigated and revealed significant inhibitory effects at sub-MIC concentrations. The influence of L-carnitine-fumarate on the phosphotransferase system was investigated as well. Our results provide a new insight into the antibacterial potential of L-carnitine-fumarate as a valuable compound to be considered for alternative or adjunct anti-caries and antibiofilm preventive approaches.

A Comparative Analysis of the Efficacy of Bacterial Lysate versus Antibiotic Therapy in the Treatment of Experimental Peri-Implantitis in Rats.

Peri-implantitis (PI) is a current concern whose understanding and resolution are ongoing. We aimed to evaluate in vivo a new treatment with antibacterial properties, based on bacterial lysates obtained from the strains of Aggregatibacter actinomycetemcomitans, Streptococcus oralis, and Fusobacterium nucleatum. This research was conducted on 30 rats with PI which were divided into three groups and treated with antibiotic and anti-inflammatory (AAi) drugs, bacterial lysates (BLs), and saline (C), respectively. The monitoring period included the clinical and paraclinical examination where hematological, immunological, imaging, and histopathological analysis were performed. No particular clinical signs were observed, but the radiological examination showed the loss of all implants in group C, in contrast to group BL which had the highest survival rate of devices. White cells showed a decrease from the PI period, as did the immunological analysis. Only IL-6 showed an increase in the AAi and BL groups. Histopathologically, the C group presented a high degree of bone destruction, and in the BL group, many attenuated inflammatory phenomena appeared compared to the AAi animals. Bacterial lysates have similar effects to antibiotic-based therapeutic regimens for PI, and their future use may help to improve the current therapeutic management of the disease.

The Distribution of Eight Antimicrobial Resistance Genes in Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii Strains Isolated from Dental Plaque as Oral Commensals.

It has been proposed that oral commensal bacteria are potential reservoirs of a wide variety of antimicrobial resistance genes (ARGs) and could be the source of pathogenic bacteria; however, there is scarce information regarding this. In this study, three common streptococci of the mitis group (S. oralis, S. sanguinis, and S. gordonii) isolated from dental plaque (DP) were screened to identify if they were frequent reservoirs of specific ARGs (blaTEM, cfxA, tetM, tetW, tetQ, ermA, ermB, and ermC). DP samples were collected from 80 adults; one part of the sample was cultured, and from the other part DNA was obtained for first screening of the three streptococci species and the ARGs of interest. Selected samples were plated and colonies were selected for molecular identification. Thirty identified species were screened for the presence of the ARGs. From those selected, all of the S. sanguinis and S. oralis carried at least three, while only 30% of S. gordonii strains carried three or more. The most prevalent were tetM in 73%, and blaTEM and tetW both in 66.6%. On the other hand, ermA and cfxA were not present. Oral streptococci from the mitis group could be considered frequent reservoirs of specifically tetM, blaTEM, and tetW. In contrast, these three species appear not to be reservoirs of ermA and cfxA.

Membrane Phenotypic, Metabolic and Genotypic Adaptations of Streptococcus oralis Strains Destined to Rapidly Develop Stable, High-Level Daptomycin Resistance during Daptomycin Exposures.

The Streptococcus mitis-oralis subgroup of viridans group streptococci are important human pathogens. We previously showed that a substantial portion of S. mitis-oralis strains (>25%) are 'destined' to develop rapid, high-level, and stable daptomycin (DAP) resistance (DAP-R) during DAP exposures in vitro. Such DAP-R is often accompanied by perturbations in distinct membrane phenotypes and metabolic pathways. The current study evaluated two S. oralis bloodstream isolates, 73 and 205. Strain 73 developed stable, high-level DAP-R (minimum inhibitory concentration [MIC] > 256 µg/mL) within 2 days of in vitro DAP passage ("high level" DAP-R [HLDR]). In contrast, strain 205 evolved low-level and unstable DAP-R (MIC = 8 µg/mL) under the same exposure conditions in vitro ("non-HLDR"). Comparing the parental 73 vs. 73-D2 (HLDR) strain-pair, we observed the 73-D2 had the following major differences: (i) altered cell membrane (CM) phospholipid profiles, featuring the disappearance of phosphatidylglycerol (PG) and cardiolipin (CL), with accumulation of the PG-CL pathway precursor, phosphatidic acid (PA); (ii) enhanced CM fluidity; (iii) increased DAP surface binding; (iv) reduced growth rates; (v) decreased glucose utilization and lactate accumulation; and (vi) increased enzymatic activity within the glycolytic (i.e., lactate dehydrogenase [LDH]) and lipid biosynthetic (glycerol-3-phosphate dehydrogenase [GPDH]) pathways. In contrast, the 205 (non-HLDR) strain-pair did not show these same phenotypic or metabolic changes over the 2-day DAP exposure. WGS analyses confirmed the presence of mutations in genes involved in the above glycolytic and phospholipid biosynthetic pathways in the 73-D2 passage variant. These data suggest that S. oralis strains which are 'destined' to rapidly develop HLDR do so via a conserved cadre of genotypic, membrane phenotypic, and metabolic adaptations.

The antibiofilm activity of selected substances used in oral health prophylaxis

Oral health is a window to a patient’s general well-being. Balance in oral microbiome functions is crucial for health maintenance. A state of oral dysbiosis may lead to a variety of local and systemic pathological conditions. The presence of dental plaque is related to the majority of oral infections. Proper oral hygiene is crucial and the most economic practice contributing to oral health prophylaxis. Aside from prophylactic treatments provided by dental practitioners, mouth rinses, containing antimicrobial agents, are one of the possible tools used for oral care. Our study was to determine whether available mouth rinses and selected products dedicated for professional use are efficient to eradicate biofilm formed by reference and clinical strains of Streptococcus mutans, Streptococcus sanguinis, Streptococcus oralis, Streptococcus mitis, Staphylococcus aureus, Enterococcus faecalis, Lactobacillus rhamnosus and Candida albicans on the surface of hydroxyapatite – major mineral component of a tooth. Therefore, such antimicrobials as chlorhexidine, cetylpyridine chloride, polyhexanide, silver nanoparticles, sulphonated phenolics, and natural antiplaque essential oils and coconut oil were analyzed. Applied experimental settings in in vitro models were designed to reflect accurately the recommended use of the tested substances, therefore four types of eradication procedure were conducted. Sialorrhea simulation was also performed to evaluate antibiofilm potential of diluted mouth rinses. Biofilm was investigated with quantitative method where absorbance values were measured. Statistical differences were assessed using the Kruskal–Wallis test with a post-hoc Dunnett’s analysis. Results have shown that biofilms displayed a diversified sensitivity to the tested antimicrobials. The highest antibiofilm activity was detected for cetylpyridine chloride while the lowest for chlorhexidine. However the differences in E. faecalis biofilm reduction observed after the use of these two compounds were not statistically significant (p > 0.05), whereas all observed differences in S. aureus survival after exposure to the examined antimicrobial agents were statistically significant (p < 0.5). The PHMB, both in standard and in sialorrhea simulated conditions had the highest potential against streptococci. The coconut oil reduced C. albicans fungus biofilm by 65.48% but low eradication level was observed in case of bacterial biofilms. The dehydrating mechanism of action of sulfonated phenolics turned out to be ineffective against streptococcal biofilm which in turn was effectively eradicated by silver nanoparticles. The implementation of Antibiofilm Dressing's Activity Measurement method allowed to observe strain-related differences in terms of antimicrobial sensitivity. The obtained results may be introduced in everyday out-patient dental plaque prophylaxis as well as clinical environment.

Effects of Propolis and Persica Mouthwashes on Three Common Oral Streptococci: A Comparative Study

Background: Dental caries and periodontal diseases are among the most common oral diseases, and research to achieve an effective strategy to overcome these diseases is necessary. One of these strategies is to use anti-septics and disinfectants, including mouthwashes. Although chlorhexidine was the first and most common mouthwash and the gold standard of anti-plaque treatments, it bears many side effects. However, herbal mouthwashes with antimicrobial properties and fewer side effects can effectively treat many of these diseases.&#x0D; Objectives: This study aimed to compare the efficiency of the two herbal types of mouthwash produced in Iran.&#x0D; Methods: The present in vitro study was conducted to investigate the anti-bacterial effects of persica and propolis mouthwashes on three strains of oral streptococci. The Zone of Inhibition (ZOI) was measured by the Disk Diffusion Method (DDM). The Minimum Inhibitory Concentration (MIC) value of each mouthwash was determined for all microorganisms using the macrodilution method.&#x0D; Results: Statistical analysis of data of DDM showed that the anti-bacterial effect of persica was significantly higher than propolis against Streptococcus. salivarius and Streptococcus. mutans (P&lt;0.001), and these two types of mouthwash had similar anti-bacterial effects on Streptococcus. sanguis. Local propolis exhibited better MIC results than persica against S. salivarius and S. mutans, and these two types of mouthwash showed similar results against S. sanguis.&#x0D; Conclusion: Local propolis was more potent than persica in preventing the growth of oral streptococci.

Expression and diversity of the sialic acid-binding adhesin and its homologs associated with oral streptococcal infection.

Streptococcus gordonii, one of the early colonizers of oral biofilms, is involved in the development of dental caries, periodontal disease, and infective endocarditis. The Hsa adhesin of S. gordonii DL1 has the ability to bind strongly to the terminal sialic acid groups of host glycoproteins via the binding region, nonrepetitive region 2 (NR2), which is important for the pathogenicity of S. gordonii DL1. Low similarity with the NR2 of Hsa homologs among other streptococcal species has been reported. However, the reports have been limited to certain strains. This study attempted to assess frequency of the expression on the bacterial cell surface and to analyze the diversity of Hsa homologs among different wild strains of oral streptococci. We isolated 186 wild-type strains of oral streptococci from healthy volunteers and analyzed their hemagglutinating (HA) activity on human erythrocytes and their Hsa homologs and NR2 homologous regions by dot immunoblotting using anti-Hsa and anti-NR2 antisera, respectively. We found 30 strains reacted with anti-NR2 antiserum (NR2 positive) and determined the sequence of the NR2 regions. Many strains with high HA activity were also NR2 positive, suggesting that the NR2 region may be associated with HA activity. Among the NR2-positive strains, four different amino acid sequence patterns were observed, demonstrating diversity in the NR2 region. Notably, S. gordonii strains frequently possessed Hsa homologs and NR2-like antigens compared with other streptococci. It is speculated that the possessing frequency of Hsa homologs and the amino acid sequence of NR2 region may vary among streptococcal species.

Inhibition of Fibrinolysis by Streptococcal Phage LysinSM1.

ABSTRACTExpression of bacteriophage lysinSM1 by Streptococcus oralis strain SF100 is thought to be important for the pathogenesis of infective endocarditis, due to its ability to mediate bacterial binding to fibrinogen. To better define the lysinSM1 binding site on fibrinogen Aα, and to investigate the impact of binding on fibrinolysis, we examined the interaction of lysinSM1 with a series of recombinant fibrinogen Aα variants. These studies revealed that lysinSM1 binds the C-terminal region of fibrinogen Aα spanned by amino acid residues 534 to 610, with an affinity of equilibrium dissociation constant (KD) of 3.23 × 10−5 M. This binding site overlaps the known binding site for plasminogen, an inactive precursor of plasmin, which is a key protease responsible for degrading fibrin polymers. When tested in vitro, lysinSM1 competitively inhibited plasminogen binding to the αC region of fibrinogen Aα. It also inhibited plasminogen-mediated fibrinolysis, as measured by thromboelastography (TEG). These results indicate that lysinSM1 is a bi-functional virulence factor for streptococci, serving as both an adhesin and a plasminogen inhibitor. Thus, lysinSM1 may facilitate the attachment of bacteria to fibrinogen on the surface of damaged cardiac valves and may also inhibit plasminogen-mediated lysis of infected thrombi (vegetations) on valve surfaces.

Evaluation of biofilm colonization on multi-part dental implants in a rat model

BackgroundPeri-implant mucositis and peri-implantitis are highly prevalent biofilm-associated diseases affecting the tissues surrounding dental implants. As antibiotic treatment is ineffective to fully cure biofilm mediated infections, antimicrobial modifications of implants to reduce or prevent bacterial colonization are called for. Preclinical in vivo evaluation of the functionality of new or modified implant materials concerning bacterial colonization and peri-implant health is needed to allow progress in this research field. For this purpose reliable animal models are needed.MethodsCustom made endosseous dental implants were installed in female Sprague Dawley rats following a newly established three-step implantation procedure. After healing of the bone and soft tissue, the animals were assigned to two groups. Group A received a continuous antibiotic treatment for 7 weeks, while group B was repeatedly orally inoculated with human-derived strains of Streptococcus oralis, Fusobacterium nucleatum and Porphyromonas gingivalis for six weeks, followed by 1 week without inoculation. At the end of the experiment, implantation sites were clinically assessed and biofilm colonization was quantified via confocal laser scanning microscopy. Biofilm samples were tested for presence of the administered bacteria via PCR analysis.ResultsThe inner part of the custom made implant screw could be identified as a site of reliable biofilm formation in vivo. S. oralis and F. nucleatum were detectable only in the biofilm samples from group B animals. P. gingivalis was not detectable in samples from either group. Quantification of the biofilm volume on the implant material revealed no statistically significant differences between the treatment groups. Clinical inspection of implants in group B animals showed signs of mild to moderate peri-implant mucositis (4 out of 6) whereas the mucosa of group A animals appeared healthy (8/8). The difference in the mucosa health status between the treatment groups was statistically significant (p = 0.015).ConclusionsWe developed a new rodent model for the preclinical evaluation of dental implant materials with a special focus on the early biofilm colonization including human-derived oral bacteria. Reliable biofilm quantification on the implant surface and the symptoms of peri-implant mucositis of the bacterially inoculated animals will serve as a readout for experimental evaluation of biofilm-reducing modifications of implant materials.

In Vitro Studies of Xylitol and Erythritol Inhibition of Streptococcus Mutans and Streptococcus Sobrinus Growth and Biofilm Production.

The aim of this study was to evaluate synergy and inhibitory effects of xylitol and erythritol on Streptococcus mutans and Streptococcus sobrinus growth and biomass production on a polystyrene plastic surface. Study design; S. mutans and sobrinus strains (American Type Culture Collection reference strains 31341, 35668, 25175, sobrinus 33478) were cultivated in media (Todd Hewitt Broth with 1% sucrose or heart-brain infusion broth with 1% sucrose) at differing concentrations of xylitol or erythritol in microtiter assay plates incubated for 48 hours. Bacterial growth was quantified and measured by optical density using a microplate reader. Experiments assessing synergy and biofilm growth were carried out also using microdilution assays. All four strains were inhibited by 30% (w/v) xylitol, and 15% erythritol at 150mg/ml erythritol, 2/4 strains had reduced growth; at 270mg/ml, 4/4 strains were inhibited. Bactericidal effects were not observed at any polyol concentration. Combinations of both polyols in a checker board array were used to determine if there were any benefits of polyol combinations. Results The combination studies yielded mixed outcomes with indifference in growth for strains 68 and 78, potential additive effect for strain 75 and possible antagonism for strain 41. Assessment of biomass formation and polyol interference were also performed post MIC assessment. Strains 41, 68 and 75 produced significant biomass in the absence of either polyol. Both polyols inhibited biomass formation in a dose-dependent fashion. Strain 75 is a poor biomass producer and could not be assessed for polyol effects in our assay. Conclusion: Our results demonstrate significant polyol influence on the oral Streptococcal strains tested in our laboratory.

Pathogenic and antimicrobial resistance genes in Streptococcus oralis strains revealed by comparative genome analysis

Streptococcus oralis is an early colonizer bacterium in dental plaques and is considered a potential pathogen of infective endocarditis (IE) disease. In this study, we built a complete genome map of Streptococcus oralis strain SOT, Streptococcus oralis strain SOD and Streptococcus infantis strain SO and performed comparative genomic analysis among these three strains. The results showed that there are five genomic islands (GIs) in strain SOT and one CRISPR in strain SOD. Each genome harbors various pathogenic genes related to diseases and drug resistance, while the antibiotic resistance genes in strains SOT and SOD were quite similar but different from those in strain SO. In addition, we identified 17 main virulence factors and capsule-related genes in three strains. These results suggest the pathogenic potential of Streptococcus strains, which lay a foundation for the prevention and treatment of a Streptococcus oralis infection.

Pneumococci Can Become Virulent by Acquiring a New Capsule From Oral Streptococci.

Pneumococcal conjugate vaccines have been successful, but their use has increased infections by nonvaccine serotypes. Oral streptococci often harbor capsular polysaccharide (PS) synthesis loci (cps). Although this has not been observed in nature, if pneumococcus can replace its cps with oral streptococcal cps, it may increase its serotype repertoire. In the current study, we showed that oral Streptococcus strain SK95 and pneumococcal strain D39 both produce structurally identical capsular PS, and their genetic backgrounds influence the amount of capsule production and shielding from nonspecific killing. SK95 is avirulent in a well-established in vivo mouse model. When acapsular pneumococcus was transformed with SK95 cps, the transformant became virulent and killed all mice. Thus, cps from oral Streptococcus strains can make acapsular pneumococcus virulent, and interspecies cps transfer should be considered a potential mechanism of serotype replacement. Our findings, along with publications from the US Centers for Disease Control and Prevention, highlight potential limitations of the 2013 World Health Organization criterion for studying pneumococcal serotypes carried without isolating bacteria. We show that an oral streptococcal strain, SK95, and a pneumococcal strain, D39, both produce chemically identical capsular PS. We also show that transferring SK95 cps into noncapsulated, avirulent pneumococcus gave it the capacity for virulence in a mouse model.

In vitro biofilm formation on different ceramic biomaterial surfaces: Coating with two bactericidal glasses

ObjectivesTo compare biofilm formation on the surface of different ceramic biomaterials to be used in implant dentistry. MethodsIn vitro biofilm formation was investigated from mixtures of standard reference strains of Streptococcus oralis, Veillonella parvula, Actinomyces naeslundii, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis. Sterile ceramic calcium hydroxyapatite discs (HA) as control, sterile Al2O3/Ce-TZP nanocomposite sandblasted discs (material A1) and sterile Al2O3/Ce-TZP nanocomposite sandblasted discs and coated with two types of antimicrobial glasses (materials A2 and A3) were used. Biofilms were grown on the four surfaces and evaluated after 12, 24, 48 and 72 h of incubation. Biofilms were examined by confocal laser scanning microscopy (CLSM). In addition, counts of live bacterial cells of the target species A. actinomycetemcomitans, F. nucleatum and P. gingivalis were calculated by quantitative polymerase chain reaction (qPCR) combined with propidium monoazide (PMA). For data analysis, bacterial counts were compared with a multivariate general lineal model. ResultsUsing CLSM, cell vitality decreased in A2 and A3. With qPCR-PMA, significant differences in vitality were observed forA. actinomycetemcomitans in A3 after 48 and 72 h of incubation. With respect to the development of the biofilms, a significant increase in counts on HA and materials A1 and A2 was observed for A. actinomycetemcomitans and F. nucleatum. Conversely, for P. gingivalis, no differences were found for HA and materials A1 and A2. SignificanceDifferences in biofilm formation were detected among the different tested materials. The ceramic material A3 has an effect on the vitality of A. actinomycetemcomitans growing in an in vitro biofilm model.

Assessment of Antibacterial and Antifungal Properties and In Vivo Cytotoxicity of Peruvian Passiflora mollisima

The antimicrobial activity of Passiflora mollissima is largely due to its aliphatic and aromatic hydrocarbons, terpenes, alkaloids, ketones, esters, alcohols, and lactones. The objective of this research was to evaluate the antimicrobial activity of the compounds in the Passiflora mollissima (Tumbo) fruit and leaves included also on cultured strains of the microorganisms Streptococcus mutans, Streptococcus oralis, Streptococcus sanguinis and Candida albicans. Antimicrobial activity was analyzed by the disk diffusion method and evaluated in terms of their zones of inhibition. The cytotoxic activity of these compounds was determined in a bioassay involving sea urchin eggs (Tetrapygusniger) in which the inhibition percentage of artificially fertilized ovules was equivalent to their cytotoxic activity after 26 hours. This study demonstrated the antimicrobial activity of ethanolic Passiflora mollissima extract against the cultured strains of Streptococcus mutans, Streptococcus oralis, and Streptococcus sanguinis with zones of inhibition after the incubation period. There was no evidence of activity against the pathogenic Candida albicans, which demonstrates a null antifungal capacity of the evaluated extracts. However, cytotoxic activity was found, and the compounds led to the complete inhibition of 100% of sea urchin ovules after 26 hours of exposure. The results of the study serve as a guide. in the industrial use of this natural resource "tumbo" due to the discovery of a potential medicine based on this plant that would be a great development in the field of antimicrobial therapies.

Detection and expression analysis of tet(B) in Streptococcus oralis

ABSTRACTTetracycline resistance can be achieved through tet genes, which code for efflux pumps, ribosomal protection proteins and inactivation enzymes. Some of these genes have only been described in either Gram-positive or Gram-negative bacteria. This is the case of tet(B), which codes for an efflux pump and, so far, had only been found in Gram-negative bacteria. In this study, tet(B) was detected in two clinical Streptococcus oralis strains isolated from the gingival sulci of two subjects. In both cases, the gene was completely sequenced, yielding 100% shared identity and coverage with other previously published sequences of tet(B). Moreover, we studied the expression of tet(B) using RT-qPCR in the isolates grown with and without tetracycline, detecting constitutive expression in only one of the isolates, with no signs of expression in the other one.This is the first time that the presence and expression of the tet(B) gene has been confirmed in Gram-positive bacteria, which highlights the potential of the genus Streptococcus to become a reservoir and a disseminator of antibiotic resistance genes in an environment so prone to horizontal gene transfer as is the oral biofilm.

Determination of copy number and circularization ratio of Tn916-Tn1545 family of conjugative transposons in oral streptococci by droplet digital PCR

ABSTRACTBackground: Tn916 and Tn1545 are paradigms of a large family of related, broad host range, conjugative transposons that are widely distributed in bacteria and contribute to the spread of antibiotic resistance genes (ARGs). Variation in the copy number (CN) of Tn916-Tn1545 elements and the circularization ratio (CR) may play an important role in propagation of ARGs carried by these elements.Objectives and Design: In this study, the CN and CR of Tn916-Tn1545 elements in oral streptococci were determined using droplet digital PCR (ddPCR). In addition, we investigated the influence of tetracycline on the CR of Tn916-Tn1545 elements.Results: The ddPCR assay designed in this study is a reliable way to rapidly determine CN and CR of Tn916-Tn1545 elements.Conclusions: Our data also suggest that Tn916-Tn1545 elements are generally stable without selective pressure in the clinical oral Streptococcus strains investigated in this study.

In vitro evaluation of antimicrobial property of silver nanoparticles and chlorhexidine against five different oral pathogenic bacteria

IntroductionNumerous antimicrobial agents are used to eliminate oral biofilm. However due to emergence of multi drug resistant microorganisms, the quest to find out biologically safe and naturally available antimicrobial agents continues. AimTo evaluate antimicrobial efficacy of silver nano-particles against five common oral pathogenic bacteria. ObjectiveTo determine antimicrobial activity of silver nanoparticles and chlorhexidine gluconate against oral pathogenic bacteria. Material and MethodWe used strains of Streptococcus mutans (MTCC 497), Streptococcus oralis (MTCC 2696), Lactobacillus acidophilus (MTCC 10307), Lactobacillus fermentum (MTCC 903), and Candida albicans (MTCC 183). We used commercially available silver nanoparticles (experimental group) and chlorhexidine gluconate (positive control). We determined minimum inhibitory concentration (MIC) minimum bactericidal concentration (MBC) of both agents and analyzed the data using paired ‘t’ test, one way ANOVA and Tucky’s post Hoc HSD. ResultSilver nanoparticles inhibited bacterial growth moderately. The mean MIC of AgNP against S. mutans was 60 ± 22.36 μg/ml, S. oralis – 45 ± 11.18 μg/ml, L. acidophilus – 15 ± 5.59 μg/ml, L. fermentum – 90 ± 22.36 μg/ml, Candida albicans – 2.82 ± 0.68 μg/ml respectively. For chlorhexidine gluconate, mean MIC for S. mutans was 300 ± 111.80 μg/ml, S. oralis – 150 ± 55.90 μg/ml, L. acidophilus – 450 ± 111.80 μg/ml, L. fermentum – 450 ± 111.80 μg/ml and Candida albicans – 150 ± 55.90 μg/ml. MIC and MBC values of AgNP were significantly lower than chlorhexidine gluconate and statistically significant (p < 0.05). ConclusionSilver nanoparticles exhibited better bacteriostatic and bactericidal effect with concentration less than five folds as compared to chlorhexidine. Silver nanoparticles when used in appropriate concentration as safe alternative to present chemically derived other antimicrobial agents.

Halitosis in children with adenoid hypertrophy

This paper attempts to identify the sources and evaluate the prevalence of halitosis in children with adenoid hypertrophy. The study included pediatric patients admitted for adenoidectomy due to obstructive symptoms. Patients with possibly other causes of halitosis, were excluded from the study. Halitosis was detected in 30 out of 136 children (22.1%). The effect of adenoid hypertrophy on halitosis was confirmed by the significant reduction in the organoleptic score rated according to the Rosenberg scale (on average by 2°) and the levels of volatile sulfur compounds (on average 84 ppb) post-adenoidectomy, as compared to pre-surgery results. In total, we reported a statistically significant decrease in the abovementioned values in 90% of patients with halitosis. It was found that in patients with halitosis, as compared to patients with no oral malodor, anaerobic bacteria and Staphylococcus aureus were more frequently observed in the adenoid tissue. Streptococcus oralis strains were more commonly reported in the material taken during adenoidectomy in children without oral malodor.

In silico assessment of virulence factors in strains of Streptococcus oralis and Streptococcus mitis isolated from patients with Infective Endocarditis.

Purpose. Streptococcus oralis and Streptococcus mitis belong to the Mitis group, which are mostly commensals in the human oral cavity. Even though S. oralis and S. mitis are oral commensals, they can be opportunistic pathogens causing infective endocarditis. A recent taxonomic re-evaluation of the Mitis group has embedded the species Streptococcus tigurinus and Streptococcus dentisani into the species S. oralis as subspecies. In this study, the distribution of virulence factors that contribute to bacterial immune evasion, colonization and adhesion was assessed in clinical strains of S. oralis (subsp. oralis, subsp. tigurinus and subsp. dentisani) and S. mitis. Methodology. Forty clinical S. oralis (subsp. oralis, subsp. dentisani and subsp. tigurinus) and S. mitis genomes were annotated with the pipeline PanFunPro and aligned against the VFDB database for assessment of virulence factors.Results/Key findings. Three homologues of pavA, psaA and lmb, encoding adhesion proteins, were present in all strains. Seven homologues of nanA, nanB, ply, lytA, lytB, lytC and iga, of importance regarding survival in blood and modulation of the human immune system, were variously present in the genomes. Few S. oralis subspecies specific differences were observed. iga homologues were identified in S. oralis subsp. oralis, whereas lytA homologues were identified in S. oralis subsp. oralis and subsp. tigurinus. Conclusion. Differences in the presence of virulence factors among the three S. oralis subspecies were observed. The virulence gene profiles of the 40 S. mitis and S. oralis (subsp. oralis, subsp. dentisani and subsp. tigurinus) contribute with important new knowledge regarding these species and new subspecies.

Synergistic antibiotic activity against planktonic and biofilm-embedded Streptococcus agalactiae, Streptococcus pyogenes and Streptococcus oralis.

To determine the antimicrobial activity against streptococcal biofilm in species mostly isolated from implant-associated infections and examine the effect of enzyme treatment of biofilm on the antimicrobial activity of different antibiotics. The activities of fosfomycin, rifampicin, benzylpenicillin, daptomycin, gentamicin, levofloxacin, proteinase K and their combinations on planktonic and/or biofilm-embedded standard laboratory strains of Streptococcus agalactiae, Streptococcus pyogenes and Streptococcus oralis were investigated in vitro by standard methods and isothermal microcalorimetry. MIC values obtained for the tested antimicrobials against planktonic bacteria ranged from 0.016 to 128 mg/L for the three species tested. Higher antibiotic concentrations were usually required to reduce biofilm in comparison with planktonic bacteria, with the exception of gentamicin, for which similar concentrations (4-16 mg/L) exerted an effect on both planktonic and biofilm cells. A synergistic effect against the streptococcal biofilm of the three species was observed when gentamicin was combined with benzylpenicillin or with rifampicin. Moreover, antibiotic concentrations comparable to the MIC observed against planktonic cells induced a strong reduction of viable bacteria in proteinase K pre-treated biofilm. This study shows that the combination of gentamicin with either benzylpenicillin or rifampicin exerts a synergistic effect against biofilms produced by the tested streptococci strains in vitro. Our results also suggest that coupling a dispersal agent with conventional antibiotics may facilitate their access to the bacteria within the biofilm. In vivo and clinical studies are needed in order to confirm whether such a strategy may be effective in the treatment of implant-associated infections caused by streptococci.