Antibiotic resistance in an in vitro subgingival biofilm model

Antibiotic lock solutions as adjunct therapy for catheter-related blood stream infections in pediatric hemodialysis patients

The predominant use of intravenous catheters as primary access type in the pediatric hemodialysis population is associated with an increased risk of catheter related blood stream infections. While strict adherence to catheter placement and long-term care guidelines have helped to decrease the incidence of these infections, blood stream infections remain an infection burden in pediatric patients with long term hemodialysis catheters. The formation of biofilms on the surfaces of these catheters has been shown to be a source of microbes causing blood stream infections. One of the strategies for preventing bacterial colonization, inhibiting microbial multiplication, and suppressing the seeding of these microbes from biofilms upon maturation, has been the use of antibiotic-based lock solutions in-between dialysis treatments. Although clinical guidelines for the use of antibiotic lock solutions are yet to be developed, available evidence suggests a beneficial role of antibiotic lock solutions in the management of catheter related blood stream infections. Additionally, a clear understanding of how biofilms are formed and their role in the pathogenesis of catheter related bloodstream infection will facilitate the development of solutions that can prevent biofilm formation and inhibit their multiplication, maturation and seeding into the bloodstream.

Inhibition of Acinetobacter baumannii Biofilm Formation Using Different Treatments of Silica Nanoparticles

There exists a multitude of pathogens that pose a threat to human and public healthcare, collectively referred to as ESKAPE pathogens. These pathogens are capable of producing biofilm, which proves to be quite resistant to elimination. Strains of A. baumannii, identified by the "A" in the acronym ESKAPE, exhibit significant resistance to amoxicillin in vivo due to their ability to form biofilm. This study aims to inhibit bacterial biofilm formation, evaluate novel silica nanoparticles' effectiveness in inhibiting biofilm, and compare their effectiveness. Amoxicillin was utilized as a positive control, with a concentration exceeding twice that when combined with silica NPs. Treatments included pure silica NPs, silica NPs modified with copper oxide (CuO.SiO2), sodium hydroxide (NaOH.SiO2), and phosphoric acid (H3PO4.SiO2). The characterization of NPs was conducted using scanning electron microscopy (SEM), while safety testing against normal fibroblast cells was employed by MTT assay. The microtiter plate biofilm formation assay was utilized to construct biofilm, with evaluations conducted using three broth media types: brain heart infusion (BHI) with 2% glucose and 2% sucrose, Loria broth (LB) with and without glucose and sucrose, and Dulbecco's modified eagle medium/nutrient (DMEN/M). Concentrations ranging from 1.0 mg/mL to 0.06 µg/mL were tested using a microdilution assay. Results from SEM showed that pure silica NPs were mesoporous, but in the amorphous shape of the CuO and NaOH treatments, these pores were disrupted, while H3PO4 was composed of sheets. Silica NPs were able to target Acinetobacter biofilms without harming normal cells, with viability rates ranging from 61-73%. The best biofilm formation was achieved using a BHI medium with sugar supplementation, with an absorbance value of 0.35. Biofilms treated with 5.0 mg/mL of amoxicillin as a positive control alongside 1.0 mg/mL of each of the four silica treatments in isolation, resulting in the inhibition of absorbance values of 0.04, 0.13, 0.07, 0.09, and 0.08, for SiO2, CuO.SiO2, NaOH.SiO2 and H3PO4.SiO2, respectively. When amoxicillin was combined, inhibition increased from 0.3 to 0.04; NaOH with amoxicillin resulted in the lowest minimum biofilm inhibitory concentration (MBIC), 0.25 µg/mL, compared to all treatments and amoxicillin, whereas pure silica and composite had the highest MBIC, even when combined with amoxicillin, compared to all treatments, but performed better than that of the amoxicillin alone which gave the MBIC at 625 µg/mL. The absorbance values of MBIC of each treatment showed no significant differences in relation to amoxicillin absorbance value and relation to each other. Our study showed that smaller amoxicillin doses combined with the novel silica nanoparticles may reduce toxic side effects and inhibit biofilm formation, making them viable alternatives to high-concentration dosages. Further investigation is needed to evaluate in vivo activity.

Weak direct current exerts synergistic effect with antibiotics and reduces the antibiotic resistance: An in vitro subgingival plaque biofilm model

BACKGROUND AND OBJECTIVE

Weak direct current (DC) exerts killing effect and synergistic killing effect with antibiotics in some specific bacteria biofilms. However, the potential of weak DC alone or combined with periodontal antibiotics in controlling periodontal pathogens and plaque biofilms remains unclear. The objective of this study was to investigate whether weak DC could exert the anti-biofilm effect or enhance the killing effect of metronidazole (MTZ) and/or amoxicillin-clavulanate potassium (AMC) on subgingival plaque biofilms, by constructing an in vitro subgingival plaque biofilm model.

METHODS

The pooled subgingival plaque and saliva of patients with periodontitis (n = 10) were collected and cultured anaerobically on hydroxyapatite disks in vitro for 48 h to construct the subgingival plaque biofilm model. Then such models were stimulated with 0 μA DC alone (20 min/12 h), 1000 μA DC alone (20 min/12 h), 16 μg/ml MTZ, 16 μg/ml AMC or their combination, respectively. Through viable bacteria counting, metabolic activity assay, quantitative real-time PCR absolute quantification and 16S rDNA sequencing analysis, the anti-biofilm effect of 1000 μA DC and enhanced killing effects of 1000 μA DC combined with antibiotics (MTZ, AMC or MTZ+AMC) were explored.

RESULTS

The old subgingival plaque model (48 h) had no significant difference in total bacterial loads from subgingival plaque in situ, which achieved a similarity of 80%. The 1000 μA DC plus MTZ or AMC for 12 h showed a stronger synergistic killing effect than the same combination for 20 min. The metabolic activity was reduced to the lowest by DC plus MTZ+AMC, as 37.4% of that in the control group, while average synergistic killing effect reached 1.06 log units and average total bacterial loads decreased to 0.87 log units. Furthermore, the relative abundance of the genera Porphyromonas, Prevotella, Treponema_2, and Tannerella were decreased significantly.

CONCLUSION

The presence of weak DC (1000 μA) improved the killing effect of antibiotics on subgingival plaque biofilms, which might provide a novel strategy to reduce their antibiotic resistance.

BIOFILM: FORMATION AND NATURAL PRODUCTS' APPROACH TO CONTROL - A REVIEW

Biofilm formation, especially on indwelling medical devices such as catheters, can result in infections and substantially affect patients' quality of life. Biofilm-associated infections have led to increased morbidity and mortality, increased cost of treatment, and length of hospital stay. However, all of the identified consequences of the biofilm-associated infections had been attributed to the reduced susceptibility of biofilm to conventional antimicrobial agents which has necessitated the development of a new strategy for biofilm infections control, thereby making a search for more effective antimicrobial agents from plant source inevitable. So far, some antimicrobial agents (crude or isolated compounds) from plant sources affect a specific stage of biofilm development while a few of them have been developed into a suitable dosage form for biofilm control. In this review, an attempt is made to look into some definitions of biofilm by "biofilmologists", stages in biofilm formation, mechanisms of resistance in biofilm, biofilm control strategies, the use of some natural products in biofilm control and concepts of probiotics as agents of biofilm control.

Antifungal Susceptibility of Candida albicans Isolated from Tongue and Subgingival Biofilm of Periodontitis Patients

The subgingival biofilm, as the most complex microbial community, has been proven to be reservoir of Candida spp. The main concept of this study was to investigate if there is a difference between the sensitivity of Candida albicans (C. albicans) isolated from tongue and subgingival areas of periodontitis patients to antifungal agents. The aim of the study was to determine: (1) the distribution of different Candida species in the tongue and subgingival samples of periodontitis patients; (2) the susceptibility of Candida albicans strains from tongue and subgingival biofilm to the effects of commonly used antifungal agents: fluconazole, amphotericin B and itraconazole; (3) the correlation between the susceptibility of Candida albicans and clinical periodontal parameters. Tongue and subgingival biofilm samples of periodontitis subjects (N = 163) were examined. Susceptibility was tested when the same Candida species was isolated from both sites (17 subjects). Candida spp. were isolated in 23.3% of tongue and 21.5% of the subgingival samples. All isolates were susceptible to amphotericin B, while 64.71% of tongue and 52.94% of subgingival isolates were susceptible to fluconazole. A low frequency of itraconazole susceptibility was observed for tongue (17.64%) and subgingival isolates (11.76%). The correlations between full-mouth plaque score and Minimal Inhibitory Concentration (MIC) for tongue isolates were strongly positive for all antimycotics. Positive correlation was also observed between moderate periodontal destruction and MICs for tongue and subgingival isolates. The susceptibility of C. albicans to antifungals correlate with oral hygiene and moderate periodontal destruction. There is no difference in antifungal susceptibility between tongue and subgingival isolates.

Study on the inhibitory effect of selective estrogen receptor modulators on Streptococcus mutans

OBJECTIVES

To screen small-molecule antibacterial drugs and investigate the antibacterial effect and mechanism of selective estrogen receptor modulators (SERMs) against Streptococcus mutans (S.mutans).

METHODS

The minimum inhibitory concentration of 426 Food and Drug Administration (FDA)-approved small-molecule drugs against S. mutans was determined using the microdilution method, and the target of SERMs acting on S. mutans was explored by employing a random transposon mutant library.

RESULTS

Among the 426 FDA-approved SERMs, toremiphene, tamoxifen, clomiphene, and raloxifene exhibited excellent antibacterial effects against S.mutans. Results of mutant library screening showed that the two mutant strains were resistant to clomiphene. The gene sequence of the resistant strains showed that the transposon insertion sites were located in the genes of smu_546 and smu_874.

CONCLUSIONS

SERMs, such as toremifene, tamoxifen, clomiphene, and raloxifene, exerted obvious antibacterial effects on S. mutans, and their targets may be proteins expressed by smu_546 and smu_874 gene.

Determination of an effective agent combination using nisin against Salmonella biofilm

This present study aims to determine the lowest concentration effects of the assayed different antibiotics; antimicrobial agents alone and their combinations with nisin were investigated to prevent the biofilm formation and break down the biofilm structure of Salmonella. While the combination of nisin and EDTA showed a synergistic effect against Salmonella strain, chlorhexidine digluconate and streptomycin with nisin showed a partial synergetic effect; citric acid and sulfonamides with nisin showed an indifferent effect. The use of citric acid and chlorhexidine digluconate alone was very effective in Salmonella inhibition. While the citric acid combined with other agents had not much effect, the use of chlorhexidine digluconate combined with nisin and EDTA inactivated the total initial count within 24 h. Significantly, when citric acid and sulfonamides are used alone, they reduce by 64% and 44%, respectively. When they used nisin + EDTA, this ratio increased to 83% and 84%, respectively. For the prevention of biofilm, the most suitable conditions were determined as 97% biofilm inhibition. The results of this study can be used as a guide for the emergence of new approaches to ensure the food safety and quality of the food industry.

Novel Phage Lysin Abp013 against Acinetobacter baumannii

As antimicrobial resistance (AMR) continues to pose an ever-growing global health threat, propelling us into a post-antibiotic era, novel alternative therapeutic agents are urgently required. Lysins are bacteriophage-encoded peptidoglycan hydrolases that display great potential as a novel class of antimicrobials for therapeutics. While lysins against Gram-positive bacteria are highly effective when applied exogenously, it is challenging for lysins to access and cleave the peptidoglycan of Gram-negative bacteria due to their outer membrane. In this study, we identify a novel phage lysin Abp013 against Acinetobacter baumannii. Abp013 exhibited significant lytic activity against multidrug-resistant strains of A. baumannii. Notably, we found that Abp013 was able to tolerate the presence of human serum by up to 10%. Using confocal microscopy and LIVE/DEAD staining, we show that Abp013 can access and kill the bacterial cells residing in the biofilm. These results highlight the intrinsic bacteriolytic property of Abp013, suggesting the promising use of Abp013 as a novel therapeutic agent.

Comparisons of the killing effect of direct current partially mediated by reactive oxygen species on Porphyromonas gingivalis and Prevotella intermedia in planktonic state and biofilm state - an in vitro study

Background/purpose

Bacterial biofilms formed on the surface of tissues and biomaterials are major causes of chronic infections in humans. Among them, Porphyromonas gingivalis (P. gingivalis) and Prevotella intermedia (P. intermedia) are anaerobic pathogens causing dental infections associated with periodontitis. In this study, we evaluated the killing effect and underlying mechanisms of direct current (DC) as an antimicrobial method in vitro.

Materials and methods

We chose P. gingivalis and P. intermedia in different states to make comparisons of the killing effect of DC. By viable bacteria counting, fluorescent live/dead staining, reactive oxygen species (ROS) assay, addition of ROS scavenger DMTU and mRNA expression assay of ROS scavenging genes, the role of ROS in the killing effect was explored.

Results

The planktonic and biofilm states of two bacteria could be effectively killed by low-intensity DC. For the killing effect of 1000 μA DC, there were significant differences whether on planktonic P. gingivalis and P. intermedia (mean killing values: 2.40 vs 2.62 log₁₀ CFU/mL) or on biofilm state of those (mean killing values: 0.63 vs 0.98 log₁₀ CFU/mL). 1000 μA DC greatly induced ROS production and the mRNA expression of ROS scavenging genes. DMTU could partially decrease the killing values of DC and downregulate corresponding gene’s expression.

Conclusion

1000 μA DC can kill P. gingivalis and P. intermedia in two states by promoting overproduction of ROS, and P. intermedia is more sensitive to DC than P. gingivalis. These findings indicate low-intensity DC may be a promising approach in treating periodontal infections.

Drug release kinetics and biological properties of a novel local drug carrier system

Background:

The purpose of this in vitro study was to investigate drug release kinetics and cytotoxicity of a novel drug delivery system for treatment of periodontitis.

Materials and Methods:

This in vitro study addresses the fabrication of a polycaprolactone/alginic acid-based polymeric film loaded with metronidazole, as a basic drug in the treatment of periodontal diseases. Films were prepared by solvent casting technique. Four formulations with different percentages of drug by weight (3%, 5%, 9%, and 13%) were prepared. Drug release kinetics were investigated using ultraviolet–visible spectroscopy during (one week). Data were analyzed using repeated measures ANOVA. Cytotoxicity of drug-loaded system extracts was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using L929 cells after 24-h incubation. The results were evaluated according to ISO standard 10993-5 and assessed using ANOVA and Tukey's tests at a significance level of P < 0.05.

Results:

All polymeric films showed a burst drug release followed by a gradual release. Drug release data were fitted well with the first-order kinetic model in all drug-containing formulations indicating that drug release is a fraction of remaining drug in the matrix. Drug release is mainly driven by diffusion of medium into the composite matrix. 3%wt metronidazole-containing formulation exhibited the best MTT result.

Conclusion:

The findings of this study supported the synthesis of drug-loaded periodontal films with 3% metronidazole due to better biological properties along with the ability of acceptable drug release to eradicate anaerobic periodontal bacteria.

Droplet-based microsystems as novel assessment tools for oral microbial dynamics

The human microbiome comprises thousands of microbial species that live in and on the body and play critical roles in human health and disease. Recent findings on the interplay among members of the oral microbiome, defined by a personalized set of microorganisms, have elucidated the role of bacteria and yeasts in oral health and diseases including dental caries, halitosis, and periodontal infections. However, the majority of these studies rely on traditional culturing methods which are limited in their ability of replicating the oral microenvironment, and therefore fail to evaluate key microbial interactions in microbiome dynamics. Novel culturing methods have emerged to address this shortcoming. Here, we reviewed the potential of droplet-based microfluidics as an alternative approach for culturing microorganisms and assessing the oral microbiome dynamics. We discussed the state of the art and recent progress in the field of oral microbiology. Although at its infancy, droplet-based microtechnology presents an interesting potential for elucidating oral microbial dynamics and pathophysiology. We highlight how new findings provided by current microfluidic-based methodologies could advance the investigation of the oral microbiome. We anticipate that our work involving the droplet-based microfluidic technique with a semipermeable membrane will lay the foundations for future microbial dynamics studies and further expand the knowledge of the oral microbiome and its implication in oral health.

Classic vs. Novel Antibacterial Approaches for Eradicating Dental Biofilm as Adjunct to Periodontal Debridement: An Evidence-Based Overview

Periodontitis is a multifactorial chronic inflammatory disease that affects tooth-supporting soft/hard tissues of the dentition. The dental plaque biofilm is considered as a primary etiological factor in susceptible patients; however, other factors contribute to progression, such as diabetes and smoking. Current management utilizes mechanical biofilm removal as the gold standard of treatment. Antibacterial agents might be indicated in certain conditions as an adjunct to this mechanical approach. However, in view of the growing concern about bacterial resistance, alternative approaches have been investigated. Currently, a range of antimicrobial agents and protocols have been used in clinical management, but these remain largely non-validated. This review aimed to evaluate the efficacy of adjunctive antibiotic use in periodontal management and to compare them to recently suggested alternatives. Evidence from in vitro, observational and clinical trial studies suggests efficacy in the use of adjunctive antimicrobials in patients with grade C periodontitis of young age or where the associated risk factors are inconsistent with the amount of bone loss present. Meanwhile, alternative approaches such as photodynamic therapy, bacteriophage therapy and probiotics showed limited supportive evidence, and more studies are warranted to validate their efficiency.

Advanced Dental Cleaning is Associated with Reduced Risk of COPD Exacerbations - A Randomized Controlled Trial

Purpose

Infections from the oral microbiome may lead to exacerbations of chronic obstructive pulmonary disease (COPD). We investigated whether advanced dental cleaning could reduce exacerbation frequency. Secondary outcomes were disease-specific health status, lung function, and whether the bacterial load and composition of plaque microbiome at baseline were associated with a difference in outcomes.

Patients and Methods

One-hundred-one primary and secondary care patients with COPD were randomized to intervention with advanced dental cleaning or to dental examination only, repeated after six months. At baseline and at 12 months, data of exacerbations, lung function, COPD Assessment Test (CAT) score, and periodontal status were collected from questionnaires, record review, and periodontal examination. Student’s t-test and Mann–Whitney-U (MWU) test compared changes in outcomes. The primary outcome variable was also assessed using multivariable linear regression with adjustment for potential confounders. Microbiome analyses of plaque samples taken at baseline were performed using Wilcoxon signed ranks tests for calculation of alpha diversity, per mutational multivariate analysis of variance for beta diversity, and receiver operating characteristic curves for prediction of outcomes based on machine learning models.

Results

In the MWU test, the annual exacerbation frequency was significantly reduced in patients previously experiencing frequent exacerbations (p = 0.020) and in those with repeated advanced dental cleaning (p = 0.039) compared with the non-treated control group, but not in the total population including both patients with a single and repeated visits (p = 0.207). The result was confirmed in multivariable linear regression, where the risk of new exacerbations was significantly lower in patients both in the intention to treat analysis (regression coefficient 0.36 (95% CI 0.25–0.52), p < 0.0001) and in the population with repeated dental cleaning (0.16 (0.10–0.27), p < 0.0001). The composition of microbiome at baseline was moderately predictive of an increased risk of worsened health status at 12 months (AUC = 0.723).

Conclusion

Advanced dental cleaning is associated with a reduced frequency of COPD exacerbations. Regular periodontal examination and dental cleaning may be of clinical importance to prevent COPD exacerbations.

Direct current exerts electricidal and bioelectric effects on Porphyromonas gingivalis biofilms partially via promoting oxidative stress and antibiotic transport

Low electric current can inhibit certain microbial biofilms and enhance the efficacy of antimicrobials against them. This study investigated the electricidal and bioelectric effects of direct current (DC) against Porphyromonas gingivalis biofilms as well as the underlying mechanisms. Here, we firstly showed that DC significantly suppressed biofilm formation of P. gingivalis in time- and intensity-dependent manners, and markedly inhibited preformed P. gingivalis biofilms. Moreover, DC enhanced the killing efficacy of metronidazole (MTZ) and amoxicillin with clavulanate potassium (AMC) against the biofilms. Notably, DC-treated biofilms displayed upregulated intracellular ROS and expression of ROS related genes (sod, feoB, and oxyR) as well as porin gene. Interestingly, DC-induced killing of biofilms was partially reversed by ROS scavenger N-dimethylthiourea (DMTU), and the synergistic effect of DC with MTZ/AMC was weakened by small interfering RNA of porin gene (si-Porin). In conclusion, DC can exert electricidal and bioelectric effects against P. gingivalis biofilms partially via promotion of oxidative stress and antibiotic transport, which offers a promising approach for effective management of periodontitis.

Profile of host cell responses to exposure to stressed bacteria in planktonic; dislodged, and intact biofilm mode

The host defense response to microbial challenge emerging from the root canal system leads to apical periodontitis. The aim of this study was to evaluate the expression of inflammatory cytokines and Nitric Oxide (NO) by macrophages after interaction with Enterococcus faecalis in the: plankton and dislodged biofilm mode; intact biofilm mode stimulated by calcium hydroxide (CH), CH and chlorhexidine (CHX) or Triple Antibiotic Paste (TAP). For this purpose, culture of macrophages from monocytes in human peripheral blood (N=8) were exposed to the different modes of bacteria for 24 hours. Subsequently, the cytokines, such as, Tumor Necrotic Factor- alfa (TNF-α), interleukin (IL)-1β, IL-6, IL-10; and NO were quantified by Luminex xMAP and Greiss reaction, respectively. In addition to the potential therapeutic effects of the intracanal medication, their antimicrobial activity against Enterococcus faecalis biofilm were also tested in vitro by confocal microscopy. The experiments` data were analyzed by the Kruskal-Wallis test with the Dunn post hoc test (α < 0.05). Bacteria in dislodged biofilm mode were shown to be more aggressive to the immune system than bacteria in plankton mode and negative control, inducing greater expression of NO and TNF-α. Relative to bacteria in intact biofilm mode, the weakest antimicrobial activity occurred in Group CH. In Groups CH/CHX and TAP the percentage of dead bacteria was significantly increased to the same extent. Interestingly, the biofilm itself did not induce the release of pro-inflammatory cytokines - except for NO - while the biofilm treated with TAP and CH based pastes enhanced the levels of IL-6 and TNF-α; and IL-1 β, respectively. In contrast, the levels of a potent anti-inflammatory (IL-10) were increased in Group TAP.

In Vitro Antibacterial Activity of Myrtus communis L. and Marrubium vulgare L. Leaves against Aggregatibacter actinomycetemcomitans and Eikenella corrodens

Materials and Methods

Clinical strains of Aggregatibacter actinomycetemcomitans and Eikenella corrodens and two reference strains of A. actinomycetemcomitans were tested. The antibacterial activity of each studied plant extract was evaluated using agar diffusion and broth microdilution assays.

Results

Both aqueous and methanolic extracts of M. communis exhibited high antibacterial activity against periodontal pathogens as compared to M. vulgare extracts. At concentrations of 2.5-0.32 mg/disc, inhibition zones of the methanolic extract of M. communis ranged from 19.66 ± 0.57 to 12.33 ± 0.57 mm. The methanolic extract of M. vulgare showed at concentrations of 5-0.63 mg/disc inhibition zones ranging from 15.66 ± 0.57 to 12 ± 0.00 mm. Its aqueous extract at concentration of 0.63 mg/disc showed no antimicrobial activity against the clinical and reference strain of A. actinomycetemcomitans. Conclusion. This study showed that methanolic and aqueous extracts of M. communis and M. vulgare have in vitro an antibacterial activity against periodontal pathogens. They could be use as ingredients of an oral antimicrobial agent for prevention or treatment of periodontal diseases. Further research on isolating the compounds from these plant extracts and their toxicity effect could be conducted.

A Repeated State of Acidification Enhances the Anticariogenic Biofilm Activity of Glass Ionomer Cement Containing Fluoro-Zinc-Silicate Fillers

This study aimed to evaluate the anticariogenic biofilm activity of a novel zinc-containing glass ionomer cement, Caredyne Restore (CR), using a flow-cell system that reproduces Stephan responses. Streptococcus mutans biofilms were cultured on either CR or hydroxyapatite (HA) discs mounted on a modified Robbins device. The media were allowed to flow at a speed of 2 mL/min for 24 h while exposed to an acidic buffer twice for 30 min to mimic dietary uptake. Acid exposure enhanced biofilm inhibition in the CR group, which showed 2.6 log CFU/mm² in viable cells and a 2 log copies/mL reduction in total cells compared to the untreated group after 24 h of incubation, suggesting enhanced anticariogenic activity due to the release of fluoride and zinc ions. However, there was no difference in the number of viable and total cells between the two experimental groups after 24 h of incubation in the absence of an acidic environment. The anticariogenic biofilm activity of CR occurs in acidic oral environments, for example in the transient pH drop following dietary uptake. CR restorations are recommended in patients at high risk of caries due to hyposalivation, difficulty brushing, and frequent sugar intake.

Experimental infection of Asian house geckos with Enterococcus lacertideformus demonstrates multiple disease transmission routes and the in-vivo efficacy of antibiotics

The disease caused by Enterococcus lacertideformus is multisystemic and ultimately fatal. Since its emergence, the bacterium has significantly impacted the captive breeding programs of the extinct in the wild Christmas Island Lister's gecko (Lepidodactylus listeri) and blue-tailed skink (Cryptoblepharus egeriae). The bacterium's pathogenicity, inability to grow in-vitro, and occurrence beyond the confines of Christmas Island necessitated the development of an experimental infection and treatment model. Asian house geckos (Hemidactylus frenatus) were challenged with a single dose of E. lacertideformus inoculum either by mouth, application to mucosal abrasion or skin laceration, subcutaneous injection, coelomic injection, or via co-housing with an infected gecko. Five healthy geckos acted as controls. Each transmission route resulted in disease in at least 40% (n = 2) geckos, expanding to 100% (n = 5) when E. lacertideformus was applied to skin laceration and mucosal abrasion groups. Incubation periods post-infection ranged between 54 and 102 days. To determine the efficacy of antibiotic treatment, infected geckos were divided into six groups (enrofloxacin 10 mg/kg, per os (PO), every 24 h (q24), amoxicillin-clavulanic acid 10 mg/kg, PO, q24, enrofloxacin 10 mg/kg combined with amoxicillin-clavulanic acid 10 mg/kg, PO, q24, rifampicin 15 mg/kg, PO, q24, clarithromycin 15 mg/kg, PO, q24, and untreated controls) for 21 days. Response to treatment was assessed by the change in lesion size, bacterial dissemination, and histological evidence of a host immune response. Irrespective of the antibiotic given, histology revealed that geckos inoculated by skin laceration were observed to have more extensive disease spread throughout the animal's body compared to other inoculation routes. The reduction in the average surface area of gross lesions was 83.6% for geckos treated with enrofloxacin, followed by the combination therapy amoxicillin-clavulanic acid and enrofloxacin (62.4%), amoxicillin-clavulanic acid (58.2%), rifampicin (45.5%), and clarithromycin (26.5%). Lesions in geckos untreated with antibiotics increased in size between 100 and 300%. In summary, enrofloxacin and amoxicillin-clavulanic acid show promising properties for the treatment of E. lacertideformus infection in geckos. The Asian house gecko E. lacertideformus infection model therefore provides foundational findings for the development of effective therapeutic treatment protocols aimed at conserving the health of infected and at-risk reptiles.

Virtual Screening and Biological Evaluation of Anti-Biofilm Agents Targeting LuxS in the Quorum Sensing System

Biofilm formation is considered as a crucial factor in various oral diseases, such as dental caries. The quorum sensing (QS) signaling system was proved to have a crucial role in the microbial dental plaque biofilm formation of Streptococcus mutans ( S. mutans). LuxS was critical to regulating the QS system and survival of the bacterium, and, therefore, compounds which target LuxS may be a potential therapy for dental caries. The binding activities of 37,170 natural compounds to LuxS were virtually screened in this study. Baicalein and paeonol were chosen for further research of the binding mode and ΔG values with LuxS. Both baicalein and paeonol inhibited the biofilm formation without influence on the growth of S. mutans. Baicalein also distinctly reduced the production of both rhamnolipids and acids. The results provide us with a new approach to combat dental caries instead of the traditional use of antibacterial chemicals.

Plasma Treatment Effects on Oral Candida albicans Biofilms

The objective of this study is to evaluate the plasma treatment effects on oral fungal biofilms. Candida albicans biofilms were developed on the 48-well plate to serve as a model of oral fungal biofilm. The treatment of 0.2% chlorhexidine digluconate (CHX) was used as a positive control compared with plasma treatments. The efficacy of treatments was determined by 3-(4,5-dimethylazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and confocal laser scanning microscope (CLSM). The survival percentage of Candida albicans decreased from 52% to 27% as the plasma power increased from 6mA to 8mA and plasma exposure time extended from 2 min to 10 min. Moreover, it was found that there is a synergistic effect of the combination of plasma and CHX treatments. Scanning electron microscopy (SEM) examination indicated severe cell damages resulting from plasma treatment. In conclusion, the low-temperature plasma treatment is effective in deactivating Candida albicans biofilms and thus provides a promising alternative to disinfect oral fungal biofilms.

Sulfated vizantin causes detachment of biofilms composed mainly of the genus Streptococcus without affecting bacterial growth and viability

BACKGROUND

Sulfated vizantin, a recently developed immunostimulant, has also been found to exert antibiofilm properties. It acts not as a bactericide, but as a detachment-promoting agent by reducing the biofilm structural stability. This study aimed to investigate the mechanism underlying this activity and its species specificity using two distinct ex vivo oral biofilm models derived from human saliva.

RESULTS

The biofilm, composed mainly of the genus Streptococcus and containing 50 μM of sulfated vizantin, detached significantly from its basal surface with rotation at 500 rpm for only 15 s, even when 0.2% sucrose was supplied. Expression analyses for genes associated with biofilm formation and bacterial adhesion following identification of the Streptococcus species, revealed that a variety of Streptococcus species in a cariogenic biofilm showed downregulation of genes encoding glucosyltransferases involved in the biosynthesis of water-soluble glucan. The expression of some genes encoding surface proteins was also downregulated. Of the two quorum sensing systems involved in the genus Streptococcus, the expression of luxS in three species, Streptococcus oralis, Streptococcus gordonii, and Streptococcus mutans, was significantly downregulated in the presence of 50 μM sulfated vizantin. Biofilm detachment may be facilitated by the reduced structural stability due to these modulations. As a non-specific reaction, 50 μM sulfated vizantin decreased cell surface hydrophobicity by binding to the cell surface, resulting in reduced bacterial adherence.

CONCLUSION

Sulfated vizantin may be a candidate for a new antibiofilm strategy targeting the biofilm matrix while preserving the resident microflora.

Evaluation of the efficacy of lycopene gel compared with minocycline hydrochloride microspheres as an adjunct to nonsurgical periodontal treatment: A randomised clinical trial

Background/purpose

The prescription of antibiotics as an adjunct to mechanical periodontal therapy in patients with severe periodontitis is recommended; however, the side effects of antibiotics are a major concern. The aim of this study was to evaluate the efficacy of lycopene (Lyc) antioxidant gel versus minocycline hydrochloride microspheres (ARISTIN) as an adjunct to the nonsurgical treatment of periodontitis.

Materials and methods

Three identical periodontal pockets/patient received root surface debridement followed by the random application of either ARISTIN, Lyc, or placebo gel (control, Ctrl). Clinical parameters, plaque index, bleeding on probing, probing pocket depth, and clinical attachment loss, were recorded at the baseline and after 30 days. Additionally, the levels of interleukin-8 (IL-8), matrix metallopeptidase 9, and tissue inhibitor of metalloproteinases 1 (TIMP1) in gingival crevicular fluid samples were assessed at the same time points.

Results

Twenty-three patients with periodontitis completed the study. Both ARISTIN and Lyc treatments showed significantly greater gains in attachment (1.94 ± 1.33 and 1.72 ± 0.88, respectively) than the Ctrl treatment (1.04 ± 0.96). Compared with those in the Ctrl, only ARISTIN showed a significant reduction in IL-8 level, whereas TIMP1 levels were significantly upregulated in the Lyc gel and ARISTIN sites. The effect size estimation indicated that Lyc gel exhibited considerably greater efficacy than the Ctrl gel.

Conclusion

Lyc gel and ARISTIN offer almost equal improvement in both clinical and biochemical parameters of periodontitis.

Antimicrobial Activity of EPA and DHA against Oral Pathogenic Bacteria Using an In Vitro Multi-Species Subgingival Biofilm Model

In search for natural products with antimicrobial properties for use in the prevention and treatment of periodontitis, the purpose of this investigation was to evaluate the antimicrobial activity of two omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), using an in vitro multi-species subgingival biofilm model including Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans. The antimicrobial activities of EPA and DHA extracts (100 µM) and the respective controls were assessed on 72 h biofilms by their submersion onto discs for 60 s. Antimicrobial activity was evaluated by quantitative polymerase chain reaction (qPCR), confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). ANOVA with Bonferroni correction was used to evaluate the antimicrobial activity of each of the fatty acids. Both DHA and EPA significantly reduced (p < 0.001 in all cases) the bacterial strains used in this biofilm model. The results with CLSM were consistent with those reported with qPCR. Structural damage was evidenced by SEM in some of the observed bacteria. It was concluded that both DHA and EPA have significant antimicrobial activity against the six bacterial species included in this biofilm model.

Dual Mode of Anti-Biofilm Action of G3 against Streptococcus mutans

Oral biofilms, formed by multiple microorganisms and their extracellular polymeric substances, seriously affect people's life. The emergence of the resistance of biofilms to conventional antibiotics and their side effects on the oral cavity have posed a great challenge in the treatment of dental diseases. Recently, antimicrobial peptides have been recognized as promising alternatives to conventional antibiotics due to their broad antibacterial spectrum, high antibacterial activity, and specific mechanism. However, the research of their anti-biofilm behaviors is still in its infancy, and the underlying mechanism remains unclear. In this study, we investigated the anti-biofilm activities of a designed helical peptide (G3) against Streptococcus mutans (S. mutans), one of the primary causative pathogens of caries. The results indicated that G3 inhibited S. mutans biofilm formation by interfering with different stages of biofilm development. At the initial stage, G3 inhibited the bacterial adhesion by decreasing the bacterial surface charges, hydrophobicity, membrane integrity, and adhesion-related gene transcription. At the later stage, G3 interacted with extracellular DNA to destabilize the 3D architecture of mature biofilms and thus dispersed them. The high activity of G3 against S. mutans biofilms, along with its specific modes of action, endows it great application potential in preventing and treating dental plaque diseases.

Adjunct use of mouth rinses with a sonic toothbrush accelerates the detachment of a Streptococcus mutans biofilm: an in vitro study

BACKGROUND

The aim of this in vitro study was to examine the possible enhancement of the biofilm peeling effect of a sonic toothbrush following the use of an antimicrobial mouth rinse.

METHODS

The biofilm at a noncontact site in the interdental area was treated by sound wave convection with the test solution or by immersion in the solution. The biofilm peeling effect was evaluated by determining the bacterial counts and performing morphological observations. A Streptococcus mutans biofilm was allowed to develop on composite resin discs by cultivation with stirring at 50 rpm for 72 h. The specimens were then placed in recesses located between plastic teeth and divided into an immersion group and a combination group. The immersion group was treated with phosphate buffer, chlorhexidine digluconate Peridex™ (CHX) mouth rinse or Listerine® Fresh Mint (EO) mouth rinse. The combination group was treated with CHX or EO and a sonic toothbrush.

RESULTS

The biofilm thickness was reduced by approximately one-half compared with the control group. The combination treatment produced a 1 log reduction in the number of bacteria compared to the EO immersion treatment. No significant difference was observed in the biofilm peeling effect of the immersion group compared to the control group.

CONCLUSIONS

The combined use of a sonic toothbrush and a mouth rinse enhanced the peeling of the biofilm that proliferates in places that are difficult to reach using mechanical stress.

Antibacterial Effect of the Natural Polymer ε-Polylysine Against Oral Pathogens Associated with Periodontitis and Caries

Antimicrobials are important adjuncts in the treatment of caries and periodontitis. However, increased bacterial resistance and hypersensitivity reactions to commonly used antimicrobials have led to an increasing demand for safe and natural substances. The objective of this study was to investigate the antibacterial effects of ε-polylysine against oral pathogens Streptococcus mutans and Porphyromonas gingivalis. Broth dilution assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) analyses were performed to explore the antibacterial effect of ε-polylysine against S. mutans strain ATCC25175 and P. gingivalis strain ATCC332277. For the test solution, ε-polylysine was added to the bacterial suspension to prepare 0.125%, 0.25%, 0.5% and 1% ε-polylysine solutions diluted in broth medium. All four concentrations demonstrated complete inhibition of S. mutans and significantly reduced viable cell counts of P. gingivalis after 24 h. From starting inoculum of 9.15 log CFU/mL, P. gingivalis cell counts reduced to 4.01 log CFU/mL in the 0.125% ε-polylysine treatment group. SEM, CLSM, and the LIVE/DEAD bacterial assay of ε-polylysine application on P. gingivalis biofilm-dentin specimens revealed bacterial cell membrane disruption and irregular cell morphologies. The results indicated satisfactory antibacterial efficacy of ε-polylysine against P. gingivalis and S. mutans in liquid medium and as an application on biofilm-dentin specimens.

Effects of timing of adjunctive systemic antibiotics on the clinical outcome of periodontal therapy: A systematic review

Background

Many systematic reviews and meta-analysis have indicated beneficial effects of adjunctive systemic antibiotics in periodontal therapy in specific situations. However, some essential issues such as the ideal time of their administration during periodontal therapy remain unanswered. This systematic review aimed to determine at which phase of periodontal treatment would adjunctive systemic antibiotics lead to the best clinical outcomes, during the active phase or in the reevaluation phase.

Material and Methods

Searches in the databases Medline, Scopus and Cochrane Library were conducted. The randomized clinical trials and retrospective cohort studies comparing the clinical benefits of adjunctive systemic antibiotic administration in the active phase of periodontal treatment versus their administration in the reevaluation phase were included. The primary outcomes assessed were differences in clinical changes in periodontal pocket depth and clinical attachment loss at all post-treatment phases.

Results

Of the 6209 records identified, two randomized clinical trials and two retrospective cohort studies were eligible according to inclusion criteria. Two studies suggested there were greater clinical benefits when systemic antibiotics were prescribed during the active phase of periodontal therapy than in the reevaluation phase while two other studies showed no significant difference in clinical outcomes at 6 months between these two different timing of administration.

Conclusions

The evidence available and evaluated in this systematic review is of heterogeneous quality and limited by the restricted number of studies and their dissimilarities in their study design and outcome reporting. Despite insufficient evidence to determine the ideal time to the adjunctive systemic antibiotic administration in the periodontal therapy, it seems that prescription of systemic antibiotic at the active phase of periodontal therapy leads to better clinical outcomes.

Key words:Active phase; periodontal therapy, periodontitis, reevaluation, systemic antibiotics, timing.

Effects of a sub-minimum inhibitory concentration of chlorhexidine gluconate on the development of in vitro multi-species biofilms

Following antimicrobial administrations in oral environments, bacteria become exposed to a sub-minimum inhibitory concentration (sub-MIC), which can induce in vitro single-species biofilms. This study explored the effects of chlorhexidine gluconate (CHG) at a sub-MIC on in vitro multi-species biofilms comprising Streptococcus mutans, Streptococcus oralis and Actinomyces naeslundii. CHG at a sub-MIC was found to induce in vitro biofilm growth, although the bacterial growth was not significantly different from that in the control. The gene transcription related to S. mutans multi-species biofilm formation with CHG at a sub-MIC was significantly higher than that of the control, but this was not found in S. mutans single-species biofilms. The bio-volume of extracellular polysaccharides with CHG at a sub-MIC was significantly higher than that of the control. This suggests that CHG at a sub-MIC may promote the development of multi-species biofilms by affecting the gene transcription related to S. mutans biofilm formation.

Effects of Ag/ZnO nanocomposite at sub-minimum inhibitory concentrations on virulence factors of Streptococcus mutans

OBJECTIVE

Streptococcus mutans (S. mutans), the main pathogen of dental caries, could be well killed by Ag/ZnO nanocomposite. However, effects on virulence factors remain to be elucidated. This study investigated effects of Ag/ZnO at sub-minimum inhibitory concentrations (sub-MICs) on virulence factors of S. mutans and related genes expressions.

DESIGN

Effects of Ag/ZnO on the growth of S. mutans was investigated by growth curves and MTT staining method. The influence of Ag/ZnO at sub-MICs on biofilm formation was measured by the crystal violet staining method and observed by a scanning electron microscopy. Adherence, cell-surface hydrophobicity, acidogenicity and extracellular polysaccharides (EPS) of S. mutans after treatment by Ag/ZnO at sub-MICs were also investigated. Virulence factors related genes expressions after treated by Ag/ZnO at 1/2 MIC was conducted by the quantitative real-time PCR (qRT-PCR) method.

RESULTS

Sub-MICs of Ag/ZnO exhibited a dose-dependent inhibition on the virulence factors of S. mutans. Specially, Ag/ZnO at 1/2 MIC decreased 69.00 % biofilm formation, 31.78 % sucrose-independent and 48.08 % sucrose-dependent adherence, 69.44 % cell-surface hydrophobicity and 72.45 % water-soluble and 90.60 % water-insoluble EPS. Furthermore, the expression of virulence factors related genes was significantly suppressed by Ag/ZnO at 1/2 MIC.

CONCLUSIONS

Ag/ZnO at sub-MICs inhibited multiple virulence factors of S. mutans through downregulating the related genes. Ag/ZnO nanocomposite could be used for prevention of dental caries at low dosage.

Oral prebiotics and the influence of environmental conditions in vitro

BACKGROUND

Only recently the concept of prebiotics has been introduced in oral health. Few potential oral prebiotics have already been identified in dual species competition assays, showing a stimulatory effect on beneficial bacteria and by this suppressing the outgrowth of pathogenic species. This study aimed to validate the effect of previously identified potential prebiotic substrates on multispecies cultures by shifting the biofilm composition towards a more beneficial species dominated microbiota.

METHODS

A chemostat culture containing 14 model oral bacterial species was used to grow biofilms for 24 hours which subsequently were treated with prebiotic solutions three times a day for 3 consecutive days. Further the influence of environmental factors such as pH, nutrient availability, oxygen concentration and prebiotic dose on the efficacy of the prebiotic substances was investigated.

RESULTS

Three potential prebiotic substrates N-acetyl-D-mannosamine, succinic acid and Met-Pro were able to bring the beneficial proportion to > 95%. While the pH of the prebiotic solution did not have an influence on the prebiotic effect, the interplay of nutrient availability, oxygen concentration and prebiotic treatment resulted in significant changes of the microbial composition identifying N-acetyl-D-mannosamine as the most promising oral prebiotic substrate. Showing a clear dose dependent effect, concentrations of N-acetyl-D-mannosamine of 1.0 and 1.5 M resulted in a biofilm composition of 97% beneficial species.

CONCLUSION

Introducing the prebiotic concept in oral health might reveal a valid approach for treatment and prevention of oral diseases and promote oral health.

Antibiofilm potential of Seabuckthorn silver nanoparticles (SBT@AgNPs) against Pseudomonas aeruginosa

In era of antibiotic resistance, antibacterial silver nanoparticles are considered as potential alternative therapeutic agent to combat drug resistant pathogens. The aim of present study was to evaluate the antibacterial, antibiofilm and biocompatible potential of green synthesized Seabuckthorn silver nanoparticles (SBT@AgNPs). In the study, antibacterial efficiency of SBT@AgNPs was studied against Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and methicillin resistant Staphylococcus aureus. SBT@AgNPs were found to possess high antibacterial activity which was indicated in terms of low minimum inhibitory and bactericidal concentrations (2-4 µg/ml) obtained against test pathogens. Anti-biofilm activity of SBT@AgNPs on young as well as mature P. aeruginosa biofilms was also evaluated. SBT@AgNPs were able to eradicate the P. aeruginosa biofilms, which was further confirmed by field emission scanning electron microscopy and confocal laser scanning microscopy. Quorum sensing assay also revealed the quorum quenching activity of SBT@AgNPs. Biocompatibility and cytocompatibility results demonstrated SBT@AgNPs to exhibit first-rate non-toxicity as no membrane damage on RBCs or detrimental morphology variation was seen in human dermal fibroblast. LC-MS analysis was also carried out to analyze the potential antibacterial chemical compounds present in aqueous extract of Seabuckthorn leaves. To the best of our knowledge this is first study in which green synthesized silver nanoparticles were exploited to eradicate young as well as mature biofilms of P. aeruginosa. Results showed that SBT@AgNPs are highly antibacterial, antibiofilm, nontoxic in nature and consequently can aid in biomedical applications.

Synergistic activity of chlorhexidine and synoeca-MP peptide against Pseudomonas aeruginosa

‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬This study aims to evaluate the in vitro antimicrobial and immunomodulatory activities and cytotoxicity of chlorhexidine (CHX) and synoeca-MP peptide alone or in combination against Pseudomonas aeruginosa. The antimicrobial property was evaluated by the determination of minimal inhibitory concentration, minimum bactericidal concentration, and planktonic bacteria and biofilm inhibition. Immunomodulatory activity was determined by enzyme-linked immunosorbent assay and nitric oxide production by the Griess reaction method. According to the results, synoeca-MP combined with CHX demonstrated antimicrobial effectiveness compared with its isolated use, in addition to immunomodulatory activity (upregulating MPC-1 and tumor necrosis factor-α and downregulating nitric oxide and interleukin-10). In this context, it is expected that the substances, together, could be capable of controlling bacterial infection and dissemination, besides potentiating macrophages' immune response against the studied microorganism. Moreover, reducing the CHX concentration by the addition of synoeca-MP peptide may, in a beneficial way, minimize the undesirable effects of both, CHX and synoeca-MP in a clinical setting.

Antimicrobial activity of red wine and oenological extracts against periodontal pathogens in a validated oral biofilm model

Background

Previous research findings support an antimicrobial effect of polyphenols against a variety of pathogens, but there is no evidence of this effect against periodontal pathogens in complex biofilms. The purpose of this study was to evaluate the antimicrobial activity of red wine and oenological extracts, rich in polyphenols, against the periodontal pathogens Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum and total bacteria growing in an in vitro oral biofilm static model.

Methods

A previously validated biofilm model, including Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, F. nucleatum, P. gingivalis and A. actinomycetemcomitans was developed on sterile hydroxyapatite discs. Red wine (and dealcoholized wine), and two polyphenols-rich extracts (from wine and grape seeds) were applied to 72 h biofilms by dipping the discs during 1 and 5 min in the wine solutions and during 30 s and 1 min in the oenological extracts. Resulting biofilms were analyzed by confocal laser scanning microscopy and viable bacteria (colony forming units/mL) were measured by quantitative polymerase chain reaction combined with propidium monoazide. A generalized linear model was constructed to determine the effect of the tested products on the viable bacterial counts of A. actinomycetemcomitans, P. gingivalis and F. nucleatum, as well on the total number of viable bacteria.

Results

The results showed that red wine and dealcoholized red wine caused reduction in viability of total bacteria within the biofilm, with statistically significant reductions in the number of viable P. gingivalis after 1 min (p = 0.008) and in A. actinomycetemcomitans after 5 min of exposure (p = 0.011) with red wine. No evidence of relevant antibacterial effect was observed with the oenological extracts, with statistically significant reductions of F. nucleatum after 30 s of exposure to both oenological extracts (p = 0.001).

Conclusions

Although moderate, the antimicrobial impact observed in the total bacterial counts and counts of A. actinomycetemcomitans, P. gingivalis and F. nucleatum, encourage further investigations on the potential use of these natural products in the prevention and treatment of periodontal diseases.

An in vitro and in vivo study of plasma treatment effects on oral biofilms

Management of dental plaque/biofilms is critical to maintain oral health. The objective of this study is to investigate the treatment effects of non-thermal atmospheric gas plasmas on oral biofilm formation and recovery under in vitro and in vivo conditions. Streptococcus mutans biofilms, a significant contributor to tooth decay, were cultured and treated by plasma. It was found that plasma treatment not only significantly reduced the in vitro biofilms, but also increased the metabolic activity of the bacteria in the biofilms. As compared with untreated control group, the cell metabolic activity, as measured by MTT assay, increased by 273%, and the aconitase activity increased by 446% for the plasma-treated group. The increased metabolic activity of the plasma-treated biofilm bacteria enhanced their susceptibility to antibiotic and host defense. An in vivo animal model using a total of 60 female rats (19 days old) were used to evaluate the anti-caries effects on the molars by 2 min of plasma treatment. It was found that, 6 months after the plasma treatment, the decayed surfaces were reduced by 62.5% on the upper molars and by 31.6% on the lower molars as compared with the untreated upper and lower molars, respectively. These in vitro and in vivo data demonstrate that the physiological state change of the biofilm due to plasma treatment provided benefit to caries control and prevention.

A New Controlled-Release Material Containing Metronidazole and Doxycycline for the Treatment of Periodontal and Peri-Implant Diseases: Formulation and In Vitro Testing

Background

Several locally administered antimicrobials have been studied in the literature as adjunctive or primary treatments for periodontitis and peri-implantitis with conflicting results.

Objective

The aim of this study was twofold: (1) the formulation of a controlled-release material containing metronidazole and doxycycline; (2) an in vitro evaluation of its antibacterial properties against planktonic and biofilm species involved in periodontal and peri-implant diseases.

Methods

Doxycycline (10 mg/ml) and metronidazole (20 mg/ml) were incorporated into a hydroxyethylcellulose-polyvinylpyrrolidone-calcium polycarbophil gel. Three milliliters of gel were dialyzed against Dulbecco's phosphate-buffered saline for 13 days. Antibiotics release at 3, 7, 10, and 13 days was determined spectroscopically. The inhibitory activity of the experimental gel was tested against A. actinomycetemcomitans, S. sanguinis, P. micra, and E. corrodens with an agar diffusion test, an inactivation biofilm test, and a confocal laser scanning microscope study (CLSMS) for S. sanguinis up to 20 days.

Results

After 13 days, the released doxycycline was 9.7% (at 3 days = 1.2 mg; 7 days = 0.67 mg; 10 days = 0.76 mg; 13 days = 0.29 mg), while metronidazole was 67% (30 mg, 6.8 mg, 2.5 mg, and 0.9 mg at the same intervals). The agar diffusion test highlights that the formulated gel was active against tested microorganisms up to 312 h. Quantitative analysis of biofilm formation for all strains and CLSMS for S. sanguinis showed a high growth reduction up to 13 days.

Conclusions

The in vitro efficacy of the newly formulated gel was confirmed both on planktonic species and on bacterial biofilm over a period of 13 days. The controlled-release gel containing metronidazole and doxycycline had an optimal final viscosity and mucoadhesive properties. It can be argued that its employment could be useful for the treatment of periodontal and peri-implant diseases, where conventional therapy seems not successful.

Administration of systemic antibiotics during non-surgical periodontal therapy-a consensus report

AIM

The aim of this meta-review was to evaluate whether there is a meaningful clinical benefit regarding the use of systemic adjunctive antibiotics in the treatment of patients with periodontitis. Additionally, a consensus regarding possible recommendations for future administration of antibiotics should be reached.

METHODS

A structured literature search was performed by two independent investigators focusing on systematic reviews (SR) covering adjunctive systemic antibiosis during non-surgical periodontal therapy. Additionally, recent randomized clinical trials (RCT, July 2015 to July 2017) were searched systematically to update the latest SR. Results were summarized and discussed in a plenary to reach a consensus.

RESULTS

Mostly, systematic reviews and RCTs showed a significant positive effect of adjunctive systematic antibiosis compared to controls. These positive effects gain clinical relevance in patients with severe periodontal disease aged 55 years and younger.

CONCLUSION

Systemic antibiotics as an adjunct to non-surgical periodontal therapy should be sensibly administered and restrictively used. Only certain groups of periodontitis patients show a significant and clinically relevant benefit after intake of systemic antibiosis during periodontal therapy.

CLINICAL RELEVANCE

Avoiding antibiotic resistance and possible side effects on the human microbiome should be a focus of dentists and physicians. Thus, a sensible administration of antibiotics is mandatory. This manuscript suggests guidelines for a reasonable use.

Chronic tonsillitis and biofilms: a brief overview of treatment modalities

Recurrent tonsillitis is described as when an individual suffers from several attacks of tonsillitis per year. Chronic and recurrent tonsillitis both cause repeated occurrences of inflamed tonsils which have a significant impact on a patient's quality of life. Numerous children suffer from recurrent tonsillitis and sore throats, and these illnesses become part of their life. Antimicrobials can provide temporary relief, but in many cases, tonsillitis recurs. The cause of such recurrent infections have been identified as microorganisms which often create biofilms and a repository of infection in the wet and warm folds of the tonsils. This review discusses different treatment modalities, their advantages and disadvantages, and new treatment options focusing on biofilms. All treatment options should be selected based on evidence and individual need.

Antibiofilm effects of amoxicillin-clavulanic acid and levofloxacin in patients with chronic rhinosinusitis with nasal polyposis

PURPOSE

Microbial biofilms have been implicated in the pathogenesis of chronic rhinosinusitis with nasal polyposis (CRSwNP). The aim of our study was to evaluate in vitro effects of amoxicillin-clavulanic acid and levofloxacin on biofilm formation by bacterial species isolated from sinus tissue in patients with CRSwNP.

METHODS

The sinus mucosal specimens were harvested from the upper parts and roof of ethmoid cavity of 48 patients with CRSwNP. Each sample was washed thoroughly in three separate beakers of sterile saline to remove any planktonic bacteria and further subjected to microbiology analysis. The biofilm-forming capacity of isolated strains was detected by microtiter-plate method and the effects of subinhibitory (1/2× to 1/16× MIC) and suprainhibitory concentrations (4, 8, 16, 32, and 64 µg/ml) of amoxicillin-clavulanic acid and levofloxacin on biofilm production were investigated.

RESULTS

Bacterial strains were isolated in 42 (87.5%) patients: one microorganism in 80.9% and two microorganisms in 19.1% of patients. The most prevalent bacteria in CRSwNP biofilms were Staphylococcus epidermidis (34%) and S. aureus (28%) followed by S. haemolyticus (12%), Pseudomonas aeruginosa (8%), Moraxella catarrhalis (6%), Streptococcus pneumoniae (6%), and other staphylococci (6%). Subinhibitory concentrations of amoxicillin-clavulanic acid and levofloxacin significantly reduced biofilm formation (p < 0.01 and p < 0.05, respectively), with better efficacy of amoxicillin-clavulanic acid (1/2-1/8× MIC) on staphylococci and levofloxacin (1/2- 1/4× MIC) on M. catarrhalis and P. aeruginosa biofilm formation. Suprainhibitory concentrations of both tested antibiotics (4-64 µg/ml) significantly eradicated mature biofilms of staphylococci (p < 0.01). The effect of levofloxacin on eradication of staphylococcal biofilms was more noticeable, compared to the effect of amoxicillin-clavulanic acid (p < 0.01). Suprainhibitory concentrations of both tested antibiotics had no effect on eradication of previously formed M. catarrhalis and P. aeruginosa biofilms (p > 0.05).

CONCLUSIONS

The amoxicillin-clavulanic acid and levofloxacin are shown to be potent antibiofilm agents in patients with CRSwNP. The effects of tested compounds depend on bacterial species and the volume of formed biofilm.

Application of bioelectric effect to reduce the antibiotic resistance of subgingival plaque biofilm: An in vitro study

Context:

Biofilms are known for their antimicrobial resistance, and so is the subgingival plaque biofilm, the primary etiologic factor for periodontal infections.

Aims:

The objective of this study is to investigate if the subgingival plaque biofilm resistance can be reduced using doxycycline in the presence of low-intensity electric field (bioelectric effect).

Settings and Design:

The study was an in vitro microbiological study.

Materials and Methods:

Subgingival plaque samples from chronic periodontitis patients were collected to grow subgingival plaque biofilms on hydroxyapatite disks. Hydroxyapatite disks with the plaque biofilms from each patient were divided into four groups: (i) No intervention – control, (ii) current alone – CU; (iii) doxycycline – AB, and (iv) combined treatment – CU + AB. After respective treatments, the disks were anaerobically incubated for 48 h, the biofilm was dispersed and subcultured and colony-forming unit/mL was estimated in all the four groups.

Statistical Analysis:

Statistical analysis was done using Mann–Whitney and Kruskal–Wallis tests for intergroup comparisons. T-test was done to assess the difference in current flow between the groups CU and CU + AB.

Results:

All the three treatment modalities showed antibacterial effect. Application of current alone resulted in reduced bacterial growth than control group. Doxycycline alone resulted in reduction in bacterial counts better than control and current alone groups. The combination treatment showed greatest inhibition of bacterial colonies.

Conclusion:

The ability of doxycycline antibiotic in inhibiting plaque biofilm was significantly enhanced by application of a weak electric field (5 volts for 2 min).

A Novel Approach for Combating Klebsiella pneumoniae Biofilm Using Histidine Functionalized Silver Nanoparticles

Treating pathogens is becoming challenging because of multidrug resistance and availability of limited alternative therapies which has further confounded this problem. The situation becomes more alarming when multidrug resistant pathogens form a 3D structure known as biofilm. Biofilms are formed in most of the infections especially in chronic infections where it is difficult to eradicate them by conventional antibiotic therapy. Chemically synthesized nanoparticles are known to have antibiofilm activity but in the present study, an attempt was made to use amino acid functionalized silver nanoparticles alone and in combination with gentamicin to eradicate Klebsiella pneumoniae biofilm. Amino acid functionalized silver nanoparticles were not only able to disrupt biofilm in vitro but also led to the lowering of gentamicin dose when used in combination. To the best of our knowledge, this is the first study demonstrating the application of amino acid functionalized silver nanoparticles in the eradication of young and old K. pneumoniae biofilm.

Silver-loaded nanotubular structures enhanced bactericidal efficiency of antibiotics with synergistic effect in vitro and in vivo

Antibiotic-resistant bacteria have become a major issue due to the long-term use and abuse of antibiotics in treatments in clinics. The combination therapy of antibiotics and silver (Ag) nanoparticles is an effective way of both enhancing the antibacterial effect and decreasing the usage of antibiotics. Although the method has been proved to be effective in vitro, no in vivo tests have been carried out at present. Herein, we described a combination therapy of local delivery of Ag and systemic antibiotics treatment in vitro in an infection model of rat. Ag nanoparticle-loaded TiO₂ nanotube (NT) arrays (Ag-NTs) were fabricated on titanium implants for a customized release of Ag ion. The antibacterial properties of silver combined with antibiotics vancomycin, rifampin, gentamicin, and levofloxacin, respectively, were tested in vitro by minimum inhibitory concentration (MIC) assay, disk diffusion assay, and antibiofilm formation test. Enhanced antibacterial activity of combination therapy was observed for all the chosen bacterial strains, including gram-negative Escherichia coli (ATCC 25922), gram-positive Staphylococcus aureus (ATCC 25923), and methicillin-resistant Staphylococcus aureus (MRSA; ATCC 33591 and ATCC 43300). Moreover, after a relative short (3 weeks) combinational treatment, animal experiments in vivo further proved the synergistic antibacterial effect by X-ray and histological and immunohistochemical analyses. These results demonstrated that the combination of Ag nanoparticles and antibiotics significantly enhanced the antibacterial effect both in vitro and in vivo through the synergistic effect. The strategy is promising for clinical application to reduce the usage of antibiotics and shorten the administration time of implant-associated infection.

Long-term clinical response to treatment and maintenance of localized aggressive periodontitis: a cohort study

AIM

To evaluate long-term clinical response to periodontal therapy and maintenance in localized aggressive periodontitis (LAP).

MATERIALS AND METHODS

One hundred forty-one African Americans diagnosed with LAP, aged 5-25 years, were enrolled. Patients underwent periodontal mechanical debridement plus 1 week of amoxicillin/metronidazole. Mechanical therapy was repeated as needed and clinical parameters were recorded at baseline, 3, 6, 12, 18 and 24 months, and two additional annual follow-up visits after treatment. Radiographs from primary dentition of patients with LAP in permanent dentition, and additional healthy siblings (HS) were analysed retrospectively.

RESULTS

Periodontal therapy significantly improved probing depth and clinical attachment level up to 4 years (mean reductions: 2.18 ± 1.03 and 2.80 ± 1.43 mm, respectively). Percentage of affected sites was reduced at all time points and maintained up to 4 years. Non-compliance with antibiotics/appointments negatively affected the treatment response. Ninety per cent of LAP patients in permanent dentition and 32% of HS presented radiographic bone loss in primary dentition.

CONCLUSIONS

Mechanical debridement with 1 week of systemic antibiotics along with proper periodontal maintenance was effective in the treatment and successful maintenance of LAP for up to 4 years. LAP in permanent dentition may be preceded in the primary dentition. Clinicaltrials.gov #NCT01330719.

[Oral care recommendations for patients with oral autoimmune bullous diseases]

BACKGROUND

Autoimmune bullous diseases (AIBD) may cause chronic oral lesions that progress insidiously.

AIMS

To provide recommendations for optimal oral-dental management of patients presenting AIBD with oral involvement.

PATIENTS AND METHODS

In the absence of scientific studies with high levels of proof, these recommendations have been drawn up at two meetings by a committee of experts on AIBD comprising 7 dermatologists, 1 stomatologist, 1 maxillofacial surgeon, 2 odontologists and 4 parodontologists.

RESULTS

The oral lesions associated with AIBD may be classified into three grades of severity: severe (generalised erosive gingivitis affecting at least 30% of dental sites), moderate (localised erosive gingivitis affecting less than 30% of dental sites) and controlled (no erosive oral lesions). Good oral-dental hygiene suited to the severity of the oral lesions, must be practised continually by these patients so as to avoid the formation of dental plaque, which aggravates symptoms. Dental and parodontal care must be considered in accordance with the severity grade of the oral lesions: in severe cases, the dental plaque must be eliminated manually with a curette, but several types of care (descaling, treatment for tooth decay, non-urgent extractions, etc.) must be suspended until the grade of severity is moderate or until the disease is stabilised.

Treatment of Oral Biofilms by a D-Enantiomeric Peptide

Almost all dental diseases are caused by biofilms that consist of multispecies communities. DJK-5, which is a short D-enantiomeric, protease-resistant peptide with broad-spectrum anti-biofilm activity, was tested for its effect on oral multispecies biofilms. Peptide DJK-5 at 10 μg/mL effectively prevented the growth of these microbes in culture media in a time-dependent manner. In addition to the prevention of growth, peptide DJK-5 completely killed both Streptococcus mutans and Enterococcus faecalis suspended from biofilms after 30 minutes of incubation in liquid culture media. DJK-5 also led to the effective killing of microbes in plaque biofilm. The proportion of bacterial cells killed by 10 μg/mL of DJK-5 was similar after 1 and 3 days, both exceeding 85%. DJK-5 was able to significantly prevent biofilm formation over 3 days (P = 0.000). After 72 hours of exposure, DJK-5 significantly reduced and almost completely prevented plaque biofilm production by more than 90% of biovolume compared to untreated controls (P = 0.000). The proportion of dead biofilm bacteria at the 10 μg/mL DJK-5 concentration was similar for 1- and 3-day-old biofilms, whereby >86% of the bacteria were killed. DJK-5 was also able to kill >79% and >85% of bacteria, respectively, after one-time and three brief treatments of 3-day-old biofilms. The combination of DJK-5 and chlorhexidine showed the best bacterial killing among all treatments, with ~83% and >88% of bacterial cells killed after 1 and 3 minutes, respectively. No significant difference was found in the percentage of biofilm killing amongst three donor plaque samples after DJK-5 treatment. In particular, DJK-5 showed strong performance in inhibiting biofilm development and eradicating pre-formed oral biofilms compared to L-enantiomeric peptide 1018. DJK-5 was very effective against oral biofilms when used alone or combined with chlorhexidine, and may be a promising agent for use in oral anti-biofilm strategies in the future.

Vizantin inhibits bacterial adhesion without affecting bacterial growth and causes Streptococcus mutans biofilm to detach by altering its internal architecture

An ideal antibiofilm strategy is to control both in the quality and quantity of biofilm while maintaining the benefits derived from resident microflora. Vizantin, a recently developed immunostimulating compound, has also been found to have antibiofilm property. This study evaluated the influence on biofilm formation of Streptococcus mutans in the presence of sulfated vizantin and biofilm development following bacterial adhesion on a hydroxyapatite disc coated with sulfated vizantin. Supplementation with sulfated vizantin up to 50 μM did not affect either bacterial growth or biofilm formation, whereas 50 μM sulfated vizantin caused the biofilm to readily detach from the surface. Sulfated vizantin at the concentration of 50 μM upregulated the expression of the gtfB and gtfC genes, but downregulated the expression of the gtfD gene, suggesting altered architecture in the biofilm. Biofilm development on the surface coated with sulfated vizantin was inhibited depending on the concentration, suggesting prevention from bacterial adhesion. Among eight genes related to bacterial adherence in S. mutans, expression of gtfB and gtfC was significantly upregulated, whereas the expression of gtfD, GbpA and GbpC was downregulated according to the concentration of vizantin, especially with 50 μM vizantin by 0.8-, 0.4-, and 0.4-fold, respectively. These findings suggest that sulfated vizantin may cause structural degradation as a result of changing gene regulation related to bacterial adhesion and glucan production of S. mutans.

Experimental Models of Oral Biofilms Developed on Inert Substrates: A Review of the Literature

The oral ecosystem is a very complex environment where more than 700 different bacterial species can be found. Most of them are organized in biofilm on dental and mucosal surfaces. Studying this community is important because a rupture in stability can lead to the preeminence of pathogenic microorganisms, causing dental decay, gingivitis, or periodontitis. The multitude of species complicates biofilm analysis so its reproduction, collection, and counting are very delicate. The development of experimental models of dental biofilms was therefore essential and multiple in vitro designs have emerged, each of them especially adapted to observing biofilm formation of specific bacteria within specific environments. The aim of this review is to analyze oral biofilm models.