Biofilm Formation on the Surfaces of CAD/CAM Dental Polymers

Dental polymers are now available as monolithic materials which can be readily used in computer-aided design and computer-aided manufacturing (CAD/CAM) systems. Despite possessing numerous advantages over conventionally produced polymers, the polymers produced by either of these systems fail to exhibit immunity to surface microbial adhesion when introduced into the oral environment, leading to the development of oral diseases. The aim of this study was to analyze the biofilm formation of six microorganisms from the oral cavity and its correlation to the surface characteristics of CAD/CAM dental polymers. A total of ninety specimens were divided into three groups: resin-based composite, polymethyl methacrylate, and polyether ether ketone. The experimental procedure included surface roughness and water contact angle measurements, colony forming unit counting, and scanning electron microscopy analysis of biofilm formed on the surface of the tested materials. The data were analyzed using the Kruskal-Wallis test, with a Dunn's post hoc analysis, and one way analysis of variance, with a Tukey's post hoc test; the correlation between the measurements was tested using Spearman's correlation coefficient, and descriptive statistics were used to present the data. Despite using the same manufacturing procedure, as well as the identical manufacturer's finishing and polishing protocols, CAD/CAM dental polymers revealed significant differences in surface roughness and water contact angle, and the increased values of both parameters led to an increase in biofilm formation on the surface of the materials. The CAD/CAM resin-based composite showed the lowest number of adhered microorganisms compared to CAD/CAM polymethyl methacrylate and CAD/CAM polyether ether ketone.

Microbial adhesion and viability on novel CAD/CAM framework materials for implant-supported hybrid prostheses

The aim of the study was to investigate the adhesion and viability of Streptococcus oralis and Candida albicans under in vitro conditions on CAD/CAM framework materials for implant-supported hybrid prostheses. Twenty-nine specimens were prepared from each of three different materials: ZR (zirconia), PEEK (polyether ether ketone) and CoCr₄ (CoCr₄ alloy). The experimental part included surface roughness (SR) and contact angle of water (CAW) measurements, followed by colony forming unit (CFU), cell viability assay and scanning electron microscopy (SEM) analyses of Strep. oralis and C. albicans biofilms on the materials' surfaces. Kruskal-Wallis and one-way analysis of variance (ANOVA) tests were used for differences between materials, and the correlation between measurements was estimated using Spearman's correlation coefficient. PEEK specimens revealed higher SR, CAW and CFU mean values, than ZR and CoCr₄ specimens. Strong positive correlation was found between SR and CFU and between CAW and CFU for both microbial species. Cell viability assay revealed similar values for both species across materials. Higher numbers of Strep. oralis and C. albicans on PEEK specimens confirm the impact of the higher surface roughness and contact angle values on the microbial adhesion and describes PEEK as less desirable than ZR and CoCr₄ from microbiological aspect.

The Anti-Biofilm Activity and Mechanism of Apigenin-7-O-Glucoside Against Staphylococcus aureus and Escherichia coli

Introduction

This study aimed to examine the anti-biofilm activity and mechanism of gallic acid (GA), kaempferol-7-O-glucoside (K7G) and apigenin-7-O-glucoside (A7G) against Staphylococcus aureus and Escherichia coli.

Methods

The antibacterial activity of the natural compounds was determined by serial dilution method. The inhibitory activity of natural compounds on biofilms was determined by crystal violet staining method. The effects and mechanisms of natural compounds on bacterial biofilms were analyzed by atomic force microscopy.

Results

In our study, compared with GA and K7G, A7G was found to exhibit the strongest anti-biofilm and antibacterial activities. The minimum biofilm inhibitory concentration (MBIC) of A7G against S. aureus and E. coli was 0.20 mg/mL and 0.10 mg/mL, respectively. The inhibition rates of 1/2 MIC of A7G on biofilms of S. aureus and E. coli were 88.9%, and 83.2% respectively. Moreover, atomic force microscope (AFM) images showed the three-dimensional biofilm morphology of S. aureus and E. coli, and the results indicated that A7G was highly effective in biofilm inhibition.

Discussion

It was found that the inhibition of A7G on biofilm was achieved through inhibiting on exopolysaccharides (EPS), quorum sensing (QS), and cell surface hydrophobicity (CSH). A7G exerted strong anti-biofilm activities by inhibiting EPS production, QS, and CSH. Hence, A7G, as a natural substance, could be a promising novel antibacterial and anti-biofilm agent for control of biofilm in food industry.

"In vivo" and "in vitro" antimicrobial activity of Origanum vulgare essential oil and its two phenolic compounds on clinical isolates of Candida spp

A limited therapeutic arsenal is currently available against Candida infections that show high resistance to antifungal agents. For this reason, there is a great need to prioritize testing therapeutic agents for the treatment of candidiasis. The use of essential oils and their phytoconstituents has been emphasized as a new therapeutic approach. The cell surface hydrophobicity (CSH), polysaccharide content, antimicrobial activity of essential oil from Origanum vulgare L. (OVEO), and its two phenolic compounds carvacrol and thymol were evaluated in four different Candida spp. (Candida albicans and emerging non-albicans Candida (NAC) species, such as C. glabrata, C. tropicalis, and C. krusei). The results showed the differences between Candida species; for example, C. tropicalis revealed higher resistance than other strains to different natural molecule treatments. The ultrastructural variabilities in the biomembranes and cell walls of these Candida spp. might explain the different biological effects observed after OVEO, carvacrol and thymol treatments. Therefore, to study the biological effects of these natural compounds on Candida strains, the samples were observed by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Moreover, the release of cellular materials and their "in vivo" antimicrobial activity on infected G. mellonella larvae were evaluated. The novelty of this study is the demonstration that exists a close correlation between both structural architecture of cell walls and biomembranes' organization with cell fungal responses to essential oils treatments. Overall, these results suggest practical limits to the predictability.

Inhibitory effect of a lipopeptide biosurfactant produced by Bacillus subtilis on planktonic and sessile cells of Trichosporon spp

The present study aimed to investigate the inhibitory effect of a bacterial biosurfactant (TIM96) on clinical strains of Trichosporon. Additionally, the effect of TIM96 on the ergosterol content, cell membrane integrity, and the hydrophobicity of planktonic cells was assessed. The inhibitory activity of TIM96 against Trichosporon biofilms was evaluated by analyzing metabolic activity, biomass and morphology. MIC values ranged from 78.125 to 312.5 μg ml^-1 for TIM96; time-kill curves revealed that the decline in the number of fungal cells started after incubation for 6 h with TIM96 at both MIC and 2×MIC. The biosurfactant reduced the cellular ergosterol content and altered the membrane permeability and the surface hydrophobicity of planktonic cells. Incubation at 10×MIC TIM96 reduced cell adhesion by up to 96.89%, thus interfering with biofilm formation. This concentration also caused up to a 99.2% reduction in the metabolic activity of mature biofilms. The results indicate potential perspectives for the development of new antifungal strategies.

Evaluation of C. Albicans and S. Mutans adherence on different provisional crown materials

PURPOSE

Bacterial adhesion on provisional crown materials retained for a long time can influence the duration for which permanent prosthetic restorations can be healthily worn in the oral cavity. The aim of this study was to compare seven different commonly used provisional crown materials with regard to Streptococcus mutans and Candida albicans surface adhesion.

MATERIALS AND METHODS

For each group, twenty specimens of the provisional fixed prosthodontic materials TemDent (Schütz), Imıdent (Imıcryl), Tab 2000 (Kerr), Structur Premium (Voco), Systemp (Ivoclar Vivadent), Acrytemp (Zhermack), and Takilon-BBF (Takilon) were prepared (diameter, 10.0 mm; height, 2.0 mm). Surface roughness was assessed by atomic force microscopy. Each group was then divided into 2 subgroups (n=10) according to the microbial suspensions used: S. mutans and C. albicans. The specimens were incubated at 37℃ with S. mutans or C. albicans for seven days. Bacterial adherence on surfaces was assessed using the 2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) assay.

RESULTS

S. mutans showed maximum adhesion to Structur, followed by Systemp, Acrytemp, Takilon, Tab 2000, Imident, and TemDent (P<.05). The highest vital C. albicans adhesion was noted on Takilon, followed by Imident and Tab 2000; the lowest adhesion was noted on Systemp (P<.05).

CONCLUSION

The materials showed significant differences in the degree of bacterial adhesion. C. albicans showed higher surface adhesion than S. mutans on provisional crown and fixed partial denture denture materials.

The HIV aspartyl protease inhibitor ritonavir impairs planktonic growth, biofilm formation and proteolytic activity in Trichosporon spp

This study evaluated the effect of the protease inhibitor ritonavir (RIT) on Trichosporon asahii and Trichosporon inkin. Susceptibility to RIT was assessed by the broth microdilution assay and the effect of RIT on protease activity was evaluated using azoalbumin as substrate. RIT was tested for its anti-biofilm properties and RIT-treated biofilms were assessed regarding protease activity, ultrastructure and matrix composition. In addition, antifungal susceptibility, surface hydrophobicity and biofilm formation were evaluated after pre-incubation of planktonic cells with RIT for 15 days. RIT (200 μg ml^-1) inhibited Trichosporon growth. RIT (100 μg ml^-1) also reduced protease activity of planktonic and biofilm cells, decreased cell adhesion and biofilm formation, and altered the structure of the biofilm and the protein composition of the biofilm matrix. Pre-incubation with RIT (100 μg ml^-1) increased the susceptibility to amphotericin B, and reduced surface hydrophobicity and cell adhesion. These results highlight the importance of proteases as promising therapeutic targets and reinforce the antifungal potential of protease inhibitors.

Glutathione as a promising anti-hydrophobicity agent against Malassezia spp

The genus Malassezia has recently attracted wide attention in medical microbiology and dermatology as a pathogen. They are lipophilic yeasts possessing high level of cell surface hydrophobicity (CSH). L-glutathione (GSH) is a ubiquitous antioxidant which offers protection against microbial infections. This study is intended to investigate the role of GSH as a potential anti-hydrophobicity agent against Malazessia spp. Microbial adherence to hydrocarbon assay was performed to assess the anti-hydrophobicity activity (AHA) of GSH against four Malassezia spp. The assay revealed that GSH at 400 μg ml(-1) concentration inhibited CSH, ranging from 84% to 95% in M. furfur, M. globosa, M. restricta and M. sympodialis without killing the cells. The AHA of GSH was corroborated by auto-aggregation assay and zeta-potential measurement, through which delayed cell aggregation was observed due to reduction in CSH level and not by modification in cell surface charge. In addition, colony-forming unit assay was performed in which 62-93% of CSH reduction was observed in Malassezia spp. tested. Furthermore, GSH treatment enhanced the sensitivity of Malassezia spp. towards human blood at the rate of 64-72%. The AHA was further confirmed through Fourier transform infrared analysis. Thus, this study portrays GSH as a prospective therapeutic alternative for Malassezia-mediated infections.

Changes in the cell surface hydrophobicity of oral Candida albicans from smokers, diabetics, asthmatics, and healthy individuals following limited exposure to chlorhexidine gluconate

OBJECTIVE

The objective of this study was to determine the cell surface hydrophobicity of 40 oral Candida albicans isolates obtained from smokers, diabetics, asthmatics using steroid inhalers, and healthy individuals, following brief exposure to subtherapeutic concentrations of chlorhexidine gluconate.

MATERIALS AND METHODS

Forty C. albicans oral isolates (10 isolates each from smokers, diabetics, asthmatics using steroid inhalers, and healthy individuals) were exposed to 3 subtherapeutic concentrations of chlorhexidine gluconate (0.00125, 0.0025, and 0.005%) for 30 min. Thereafter, the antiseptic was removed and the cell surface hydrophobicity was measured by a biphasic aqueous-hydrocarbon assay.

RESULTS

Compared to the unexposed controls, the cell surface hydrophobicity of C. albicans isolates was suppressed by 5.40% (p > 0.05), 21.17% (p < 0.05), and 44.67% (p < 0.05) following exposure to 0.00125, 0.0025, and 0.005% chlorhexidine gluconate, respectively.

CONCLUSIONS

A brief period of transient exposure to subtherapeutic concentrations of chlorhexidine gluconate may modulate the cell surface hydrophobicity of C. albicans isolates and thereby may reduce candidal pathogenicity.

Candida colonisation and the efficacy of chlorhexidine gluconate on soft silicone-lined dentures of diabetic and non-diabetic patients

OBJECTIVES

The aim of this study was to evaluate Candida colonisation in the dentures with silicone soft liner in diabetic and non-diabetic patients and to assess the antifungal efficacy of chlorhexidine gluconate on Candida colonies.

MATERIALS AND METHODS

Thirty patients with resorbed ridges, fifteen each in the diabetic and non-diabetic group, were selected. The mandibular denture of each patient was lined with heat-polymerised silicone resilient liner. Patients were instructed to clean the dentures with soap water and brush. Samples from the fitting surface of mandibular dentures were collected at 15, 21 and 30 days. Subsequently, samples were collected at 15, 21 and 30 days, after cleaning the dentures with a detergent solution of 4% chlorhexidine gluconate, and incubated for the evaluation of Candida growth. These data were subjected to statistical analysis by Mann-Whitney U-test.

RESULTS

Normal oral flora in diabetics and non-diabetics showed no difference (p > 0.05). The density of colonies increased after 21 and 30 days in diabetic patients (p < 0.05). Number of Candida colonies significantly reduced in both the groups after 21 and 30 days of cleaning the dentures with 4% chlorhexidine gluconate (p < 0.05).

CONCLUSION

Dentures with silicone resilient liner exhibit increased Candida growth in diabetic patients. Four per cent chlorhexidine gluconate solution effectively disinfects these dentures.

Cell surface hydrophobicity of oral Candida dubliniensis isolates following limited exposure to sub-therapeutic concentrations of chlorhexidine gluconate

Candidal adhesion has been implicated as the initial step in the pathogenesis of oral candidiasis and cell surface hydrophobicity (CSH) has been implicated in adhesion to mucosal surfaces. Candida dubliniensis is an opportunistic pathogen associated with recurrent oral candidiasis. Chlorhexidine gluconate is by far the commonest antiseptic mouth wash prescribed in dentistry. At dosage intervals the intraoral concentration of this antiseptic fluctuates considerably and reaches sub-therapeutic levels due to the dynamics of the oral cavity. Hence, the organisms undergo only a limited exposure to the antiseptic during treatment. The impact of this antiseptic following such exposure on CSH of C. dubliniensis isolates has not been investigated. Hence, the main objective of this study was to investigate the effect of brief exposure to sub-therapeutic concentrations of chlorhexidine gluconate on the CSH of C. dubliniensis isolates. Twelve oral isolates of C. dubliniensis were briefly exposed to three sub-therapeutic concentrations of 0.005%, 0.0025% and 0.00125% chlorhexidine gluconate for 30 min. Following subsequent removal of the drug, the CSH of the isolates was determined by a biphasic aqueous-hydrocarbon assay. Compared with the controls, exposure to 0.005% and 0.0025% chlorhexidine gluconate suppressed the relative CSH of the total sample tested by 44.49% (P < 0.001) and 21.82% (P < 0.018), respectively, with all isolates being significantly affected. Although exposure to 0.00125% of chlorhexidine gluconate did not elicit a significant suppression on the total sample tested (7.01%; P > 0.05), four isolates of the group were significantly affected. These findings imply that exposure to sub-therapeutic concentrations of chlorhexidine gluconate may suppress CSH of C. dublinienis isolates, thereby reducing its pathogenicity and highlights further the pharmacodynamics of chlorhexidine gluconate.

Effects of subtherapeutic concentrations of chlorhexidine gluconate on germ tube formation of oral Candida

OBJECTIVE

The main objective of this study was to investigate the effect of brief exposure to subtherapeutic concentrations of chlorhexidine gluconate on germ tube formation of Candida albicans isolates obtained from smokers, diabetics, asthmatics using steroid inhalers and healthy individuals.

MATERIALS AND METHODS

Forty isolates of C. albicans were used in this study. All these isolates were quantified for germ tube formation without exposure to the drug and were used as the control group for data analysis. Isolates were also exposed to three subtherapeutic concentrations of chlorhexidine gluconate (0.00125, 0.0025 and 0.005%) for 30 min (limited exposure); the antiseptic was then removed and germ tube formation of these isolates was quantified microscopically following incubation in a germ tube-inducing medium.

RESULTS

Compared with the unexposed controls, brief exposure to all concentrations of chlorhexidine gluconate suppressed the ability of the C. albicans isolates to form germ tubes in increasing order by 13.72% (p < 0.001 to p = 0.02), 46.16% (p < 0.001) and 72.46% (p <0.001).

CONCLUSIONS

These findings show that brief exposure to subtherapeutic concentrations of chlorhexidine gluconate may modulate germ tube formation of C. albicans isolates, thereby suppressing their pathogenicity, and further elucidate the pharmacodynamic mechanisms by which chlorhexidine gluconate may operate in vivo.

Silicone colonization by non-Candida albicans Candida species in the presence of urine

Urinary tract infections (UTIs) are the most common nosocomial infections and 80 % are related to the use of urinary catheters. Furthermore, Candida species are responsible for around 15 % of UTIs and an increasing involvement of non-Candida albicans Candida (NCAC) species (e.g. Candida glabrata, Candida tropicalis and Candida parapsilosis) has been recognized. Given the fact that silicone is frequently used in the manufacture of urinary catheters, the aim of this work was to compare both the adhesion and biofilm formation on silicone of different urinary clinical isolates of NCAC species (i.e. C. glabrata, C. tropicalis and C. parapsilosis) in the presence of urine. Several clinical isolates of NCAC species recovered from patients with UTIs, together with reference strains of each species, were examined. Adhesion and biofilm formation were performed in artificial urine and the biofilm biomass was assessed by crystal violet staining. Hydrophobicity and surface charge of cells was determined by measuring contact angles and zeta potential, respectively. The number of viable cells in biofilms was determined by enumeration of c.f.u. after appropriate culture. The biofilm structure was also examined by confocal laser scanning microscopy (CLSM). The results showed that all isolates adhered to silicone in a species- and strain-dependent manner with C. parapsilosis showing the lowest and C. glabrata the highest levels of adhesion. However, these differences in adhesion abilities cannot be correlated with surface properties since all strains examined were hydrophilic and exhibited a similar zeta potential. Despite a higher number of cultivable cells being recovered after 72 h of incubation, stronger biofilm formation was not observed and CLSM showed an absence of extracellular polymeric material for all isolates examined. In summary, this work demonstrated that all tested NCAC species were able to adhere to and survive on silicone in the presence of urine. Furthermore, C. glabrata strains presented higher colonization abilities than C. tropicalis and C. parapsilosis strains, a fact that might explain the larger role of C. glabrata colonization and disseminated infections in hospitalized and catheterized patients.

Use of antifungal agents for oral candidiasis: results of a national survey

BACKGROUND

Candida albicans is an opportunistic agent that colonizes the oral mucosa.

OBJECTIVES

To determine the attitude of Spanish dentists toward the oral treatment of candidiasis.

METHOD

Between May and November 2006, a questionnaire was circulated to a random selection of 1134 dentists obtained from the General Dental Council's main list. The survey consisted of a block of socio-demographic items followed by another block related to the diagnosis and treatment of oral candidiasis. Replies to the questionnaire were received from 840 (74%) dentists.

RESULTS

50.4% of respondents were men, and 48.1% were female with a mean age of 38 and 12.2 years of professional experience. Miconazole was the most popular choice of antifungal agent prescribed (59.3%), followed by nystatin (57.7%) for topical use. Systemic antifungal agents were used by 30.20% of dentists, with a strong association between their use and the number of years in practice, gender and professional qualifications (P < 0.005).

CONCLUSION

Most Spanish dentists make clinical diagnosis and treat oral infections by C. albicans themselves with topical drugs (miconazole and nystatin) as a first choice. Systemic treatments are more commonly chosen by male dentists with long professional experience, especially by stomatologists.

Triamcinolone acetonide mouth rinses for treatment of erosive oral lichen planus: efficacy and risk of fungal over-infection

OBJECTIVES

To assess the efficacy of triamcinolone acetonide mouthrinse for treatment of erosive oral lichen planus (OLP), and to evaluate the risk of fungal over-infection.

PATIENTS AND METHODS

Clinical records of all cases of erosive and erosive-ulcerative OLP treated in our Oral Medicine Service over the period 1993-2003 were reviewed. All patients had been treated with mouthrinses containing triamcinolone acetonide at 0.3% (T1) or 0.5% (T2). Clinical outcome for each patient was classified at 1, 3 and 6 months after start of treatment as total remission (TR), partial remission (PR) or no remission (NR). Fungal over-infection was also recorded.

RESULTS

A total of 35 cases were included in the study. Clinical outcomes considering both treatment groups together (T1 + T2) were as follows: at month 1, 28.6% TR, 62.9% PR, 8.6% NR; at month 3, 57.1% TR, 37.1% PR, 5.7% NR; and at month 6, 80.0% TR, 17.1% PR, 2.9% NR. In four patients (11.4%) fungal over-infection was noted during the study period.

CONCLUSION

Triamcinolone acetonide mouthrinse is an appropriate treatment for erosive OLP, in view of the high efficacy and low risk of fungal over-infection.

Effect of aqueous extract from Neem (Azadirachta indica A. Juss) on hydrophobicity, biofilm formation and adhesion in composite resin by Candida albicans

OBJECTIVE

Azadirachta indica, a Meliaceae family tree, has been used in India for many years in the treatment of several diseases in medicine and dentistry. Current research analyses the effects of the leaf aqueous extract from Azadirachta indica (Neem) on the adhesion, cell surface hydrophobicity and biofilm formation, which may affect the colonisation by Candida albicans.

METHODS

Azadirachta indica extract was tested in vitro on strains of Candida albicans 12A and 156B. Changes in hydrophobicity were reported in assays of yeast adhesion to hydrocarbons, in biofilm formation with glucose and in the adhesion of the microorganisms on light cured composite resin. Assays involved enumeration of candidal colony-forming units together with scintillation counting of radiolabelled Candida and compared to a solution of chlorhexidine digluconate 0.125% widely used in dentistry.

RESULTS

Yeast growth in Neem extract was not inhibited in concentrations ranging from 0.1mg/ml. A statistically significant increase (p<0.05) in cell surface hydrophobicity was evident for the two strain tested and there was also an associated increase in biofilm formation after contact with Neem extract in concentration 0.01 g/ml. Decrease in adhesion capacity of cells to composite resin was also recorded.

CONCLUSION

An anti-adhesive mechanism of action by Azadirachta indica is proposed based on the results observed.