Investigation of adhesion status of Candida species to the surface of resin materials produced at different angles with additive manufacturing.

BACKGROUND: The aim of this study was to evaluate the adhesion of Candida glabrata, Candida albicans, Candida krusei, Candida parapsilosis and Candida tropicalis yeasts to disk-shaped resin materials produced from resin which used in the production of surgical guide with 0, 45 and 90-degrees printing orientations by Liquid Crystal Display additive manufacturing technology. METHODS: Disk-shaped specimens were printed with surgical guide resin using the Liquid Crystal Display production technique in 3 printing orientations (0, 45 and 90-degrees). Surface roughness and contact angle values were evaluated. Real-Time PCR analysis was performed to evaluate Candida adhesion (C. glabrata, C. albicans, C. krusei, C. parapsilosis and C. tropicalis) Field emission scanning electron microscope (FESEM) images of the materials were obtained. RESULTS: Specimens oriented at 45-degrees demonstrated higher surface roughness (P < .05) and lower contact angle values than other groups. No significant difference was found in the adhesion of C. glabrata, C. albicans, and C. parapsilosis among specimens printed at 0, 45, and 90-degrees orientations (P > .05). A higher proportion of C. krusei and C. tropicalis was found in the specimens printed at orientation degrees of 45 = 90 < 0 with statistical significance. Analyzing the adhesion of all Candida species reveals no statistical disparity among the printing orientations. CONCLUSIONS: The surface roughness, contact angle, and adhesion of certain Candida species are affected by printing orientations. Hence, careful consideration of the printing orientation is crucial for fabricating products with desirable properties. In 45-degree production, roughness increases due to the layered production forming steps, whereas in 0-degree production, certain Candida species exhibit high adhesion due to the formation of porous structures. Consequently, considering these factors, it is advisable to opt for production at 90-degrees, while also considering other anticipated characteristics.

Porcine intestinal glycosphingolipids recognized by Brachyspira hyodysenteriae.

Swine dysentery caused by Brachyspira hyodysenteriae is a disease present worldwide with an important economic impact on the farming business, resulting in an increased use of antibiotics. In the present study, we investigated the binding of B. hyodysenteriae to glycosphingolipids from porcine small intestinal epithelium in order to determine the glycosphingolipids involved in B. hyodysenteriae adhesion. Specific interactions between B. hyodysenteriae and two non-acid glycosphingolipids were obtained. These binding-active glycosphingolipids, were characterized by mass spectrometry as lactotetraosylceramide (Galß3GlcNAcß3Galß4Glcß1Cer) and the B5 glycosphingolipid (Galα3Galß4GlcNAcß3Galß4Glcß1Cer). Comparative binding studies using structurally related reference glycosphingolipids showed that B. hyodysenteriae binding to lactotetraosylceramide required an unsubstituted terminal Galß3GlcNAc sequence, while for binding to the B5 pentaosylceramide the terminal Galα3Galß4GlcNAc sequence is the minimum element recognized by the bacteria. Binding of Griffonia simplicifolia IB4 lectin to pig colon tissue sections from healthy control pig and B. hyodysenteriae infected pigs showed that in the healthy pigs the Galα3Gal epitope was mainly present in the lamina propria. In contrast, in four out of five pigs with swine dysentery there was an increased expression of Galα3Gal in the goblet cells and in the colonic crypts, where B. hyodysenteriae also was present. The one pig that had recovered by the time of necropsy had the Galα3Gal epitope only in the lamina propria. These data are consistent with a model where a transient increase in the carbohydrate sequence recognized by the bacteria occur in colonic mucins during B. hyodysenteriae infection, suggesting that the mucins may act as decoys contributing to clearance of the infection. These findings may lead to novel strategies for treatment of B. hyodysenteriae induced swine dysentery.

Plasmonic probing of the adhesion strength of single microbial cells.

Probing the binding between a microbe and surface is critical for understanding biofilm formation processes, developing biosensors, and designing biomaterials, but it remains a challenge. Here, we demonstrate a method to measure the interfacial forces of bacteria attached to the surface. We tracked the intrinsic fluctuations of individual bacterial cells using an interferometric plasmonic imaging technique. Unlike the existing methods, this approach determined the potential energy profile and quantified the adhesion strength of single cells by analyzing the fluctuations. This method provides insights into biofilm formation and can also serve as a promising platform for investigating biological entity/surface interactions, such as pathogenicity, microbial cell capture and detection, and antimicrobial interface screening.

Surface Characteristics and Microbial Adhesion in Polymethylmethacrylate for Denture Base Submitted to Antimicrobial Agents and Cleaning Agents: A Systematic Review.

This review aimed to identify the influence of antimicrobial and cleaning agents on surface characteristics such as surface free energy (SFE) and wettability, and microbial adhesion in polymethylmethacrylate (PMMA) for denture base. The review question, based on PICO, was: "Does intervention with antimicrobial and cleaning agents in PMMA influence the surface free energy, wettability, and consequently the microbial adhesion?" and the protocol was registered in Open Science Framework (osf. io/v3xgn). The search was performed in PubMed, Lilacs, Embase, Scopus, and Science Direct databases, using the terms: ("acrylic resin" OR PMMA) AND (antimicrobial OR antibacterial) AND ("electrostatic interaction" OR surface free energy) AND (biofilm OR "bacteria adhesion"), and resulted in 462 articles, of which 7 were included. The antimicrobials polypara-xylylene, carboxybetaine methacrylate, ethylene glycol methacrylate phosphate, and deposition of F and Ag ions in PMMA influenced the SFE and wettability. Denture cleaners reduced microbial adhesion. Five of the included studies evaluated the microbial adhesion, however, only two observed a direct relationship between SFE, wettability, and microbial adhesion. It was concluded that the intervention with antimicrobial and cleaning agents in PMMA can interfere in SFE and surface wettability, but no correlation was observed between microbial adhesion and these surface characteristics in PMMA.

Understanding inactivation of Listeria monocytogenes and Escherichia coli O157:H7 inoculated on romaine lettuce by emulsified thyme essential oil.

Effects of thyme essential oil (TEO) emulsion (TEE) with cationic charge formulated using cetylpyridinium chloride (CPC) on attachment strength and inactivation of Listeria monocytogenes and Escherichia coli O157:H7 on romaine lettuce surface were examined in this study. Regardless of the inoculation time (2 h and 24 h), pathogen attachment was stronger on the adaxial surface of the romaine lettuce than on the abaxial surface because of the lower roughness of the former. Moreover, attachment strength increased with increasing inoculation time. TEE washing had the strongest inhibitory effect on pathogen attachment at 2 h when compared with that of TEO, CPC, and sodium hypochlorite (SH), demonstrating a 3.32 and 2.53 log-reduction in the size of the L. monocytogenes and E. coli O157:H7 populations, respectively, compared to the control samples. Additionally, the TEE washing effects were maintained even after inoculation for 24 h, and it decreased attachment to adaxial surface of the samples. These results indicate that TEE could be a good alternative to SH in improving the microbiological safety of romaine lettuce.

In vitro study of surface properties and microbial adhesion of various dental polymers fabricated by different manufacturing techniques after thermocycling.

OBJECTIVES: The study aims to investigate surface properties and microbial adhesion of various dental polymers fabricated by different manufacturing techniques before and after thermocycling. MATERIALS AND METHODS: The following six materials were used to fabricate disk-shaped specimens: conventional denture polymer (Vertex Acrylic Resin, VAR), CAD/CAM denture polymer (Organic PMMA eco Pink, OP), conventional temporary polymer (Protemp™ 4, PT), CAD/CAM temporary polymer (Die Material, DM), conventional denture framework polymer (BioHPP, PB), and CAD/CAM denture framework polymer (breCAM.BioHPP, CB). The specimens were tested before and after thermocycling (5000 and 10,000 cycles, 5 °C/55 °C). Surface roughness (SR), hydrophobicity, and surface topography were determined by profilometry, water contact angle, and scanning electron microscopy (SEM). Then specimens were incubated with Staphylococcus aureus, Streptococcus mutans, and Candida albicans for 24 h, respectively. Microbial adhesion was assessed using colony-forming unit counts, XTT assay, and SEM. RESULTS: SR and hydrophobicity of VAR group were higher than that of OP group. S. aureus and C. albicans adhesion on VAR and PT groups were higher than that on OP and DM groups, respectively. There was no difference in surface properties and microbial adhesion between PB and CB groups. After thermocycling, SR (expect OP group) of all materials increased and hydrophobicity decreased, and the amount and activity of S. aureus and C. albicans adhesion also increased. The adhesion of S. aureus and C. albicans showed a moderate positive correlation with SR, independent of hydrophobicity. CONCLUSIONS: CAD/CAM denture polymers and temporary polymers showed less S. aureus and C. albicans adhesion when compared to conventional ones, which were mainly affected by surface roughness, independent of hydrophobicity. Thermocycling could increase surface roughness, decrease hydrophobicity, and affect microbial adhesion of the materials. CLINICAL SIGNIFICANCE: CAD/CAM dental polymers may be a better choice for the manufacture of temporary restorations and dentures to reduce microbial adhesion.

Potential of Carvacrol and Thymol in Reducing Biofilm Formation on Technical Surfaces.

Polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and stainless steel (SS) are commonly used in medicine and food production technologies. During contact with microorganisms on the surface of these materials, a microbial biofilm is formed. The biofilm structure is difficult to remove and promotes the development of pathogenic bacteria. For this reason, the inhibition of biofilm formation in medical and food production environments is very important. For this purpose, five naturally occurring compounds were used for antimicrobial screening tests. The two with the best antimicrobial properties were chosen to inhibit the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. After 3 days of exposure, thymol reduced the amount of biofilm of Pseudomonas aeruginosa within the range of 70-77% and 52-75% for Staphylococcus aureus. Carvacrol inhibited the formation of biofilms by up to 74-88% for Pseudomonas aeruginosa and up to 86-100% for Staphylococcus aureus. Those phenols decreased the enzyme activity of the biofilm by up to 40-100%. After 10 days of exposure to thymol, biofilm formation was reduced by 80-100% for Pseudomonas aeruginosa and by about 79-100% for Staphylococcus aureus. Carvacrol reduced the amount of biofilm by up to 91-100% for Pseudomonas aeruginosa and up to 95-100% for Staphylococcus aureus.

In vitro adherence of Candida albicans to zirconia surfaces.

OBJECTIVES: This study aimed to characterize surface properties such as roughness (Ra) and surface-free energy (SFE) of glazed and polished yttria-stabilized zirconia and to evaluate in vitro adherence of fungus Candida albicans and salivary bacteria, Staphylococcus epidermidis, mixed with C. albicans to these substrata. Additionally, the influence of salivary proteins (albumin, mucin and α-amylase) on yeast adhesion was studied. MATERIAL AND METHODS: Ra and SFE of glazed and polished zirconia discs were measured. Specimens were wetted with saliva and salivary proteins prior to incubation with C. albicans and mixed suspension of C. albicans and S. epidermidis for 24 hr, respectively. Microbial adhesion was quantified by counting colony-forming units (CFU). Differences in physicochemical properties were proved by t test. "Linear mixed model" with the factors "type of surface" and "wetting media" was applied to analyse the effects on fungal adhesion (p < .05). RESULTS: SFE and Ra of glazed specimens were significantly higher than corresponding values of polished ones. The wetting media significantly changed the fungal binding (p = .0016). Significantly higher quantities of adhering fungi were found after mucin incubation compared to saliva (p = .004). For the factor "surface" as well as the interaction between "surface" and "wetting media," no statistically significant differences have been found. In mixed suspension, the growth of Candida was completely prevented. CONCLUSIONS: Glazed and polished zirconia differs in terms of physicochemical surface properties. These differences appear to be modulated by pellicle coating affecting the biomass of adhered Candida. Mucin seems to be good binding sites for adhesion of C. albicans.

Evaluation of adhesion of Streptococcus mutans, plaque accumulation on zirconia and stainless steel crowns, and surrounding gingival inflammation in primary molars: randomized controlled trial.

OBJECTIVE: To evaluate the adhesion of Streptococcus mutans to preformed zirconia and stainless steel crowns and compare plaque accumulation and gingival inflammation over a period of 1 year. MATERIALS AND METHODS: Thirty children between 6 to 9 years with pulpectomised bilateral mandibular primary second molars were randomly divided into zirconia/stainless steel groups. Plaque was collected from the crowns using swabs at 3, 6, 9, and 12 months. Gingival and plaque index were recorded at all follow-ups. S. mutans was cultured on tryptone-yeast-cysteine-sucrose-bacitracin agar, and organisms were expressed as colony-forming units. Within-group analysis was performed using repeated measures ANOVA and between-groups using the independent T test. RESULTS: S. mutans were found in significantly higher numbers on the stainless steel crowns as compared with zirconia crowns at all the follow-ups. Gingival inflammation and plaque index scores were also significantly higher around the stainless steel crowns as compared with zirconia at the end of 12 months follow-up. CONCLUSION: Adhesion of S. mutans to stainless steel crowns was significantly greater when compared with zirconia, and minimal gingival inflammation and plaque accumulation was found in the tooth restored with zirconia crowns as compared with stainless steel crowns. CLINICAL RELEVANCE: Preformed zirconia crowns prevents adhesion of S. mutans onto its surface, and reduces plaque accumulation around the crown, inflammation of surrounding gingiva compared to conventional stainless-steel crowns. Pediatric zirconia crowns could help in reducing the overall microbial density and prevalence in the oral cavity, thus reducing the caries risk in the long term.

[Experimental study of a bacterial adhesion to titanium plates used for osteosynthesis of facial bones]. / Rezul'taty izucheniya adgezii mikroorganizmov k titanovym plastinam, ispol'zuemym pri osteosinteze kostei litsevogo skeleta, v eksperimente.

BACKGROUND: The adhesion ability of microorganisms to the surface of titanium miniplates and screws is one of factors in the development of purulent-inflammatory complications in the postoperative period. One of the solutions to this problem is the use of an ion-plasma coating of mini-plates and screws. OBJECTIVE: The aim of the study was to prove a decrease adhesion level of pathogenic and conditionally pathogenic bacterium to samples of titanium mini-plates with ion-plasma coating, compared with samples without coating. MATERIAL AND METHODS: Present opinion about microbial adhesion, how the most important stage of development microbial colonization of abiotic surfaces, was been basis of this study. The strains of aerobic and facultative anaerobic pathogens, as well as the non-spore-forming (non-clostridial) obligate-anaerobic pathogens were used in the research. During the experiments the standard method for determining residual adhesion was applied. The data obtained were processed by the «Biostat 9.0¼ software package. For the data received by the methods of variational parametric and nonparametric statistics we used the Mann-Whitney test, taking into account the average value, error, and the number of observations (significance of differences at p<0.05). RESULTS: As a result, the differences between the indices residual adhesion of strains aerobic and facultative anaerobic pathogens on the samples with and without a protective coating were statistically reliable, however, the adhesion of the individual species varied. The same differences between the indices residual adhesion were obtained among the strains of obligate anaerobic pathogens. The low level of adhesion, which was observed in the case of using the protective coating, is a very promising way of development, since these microorganisms are dangerous as the may lead to the development of purulent-inflammatory complications and the rejection of implants. CONCLUSION: The decreased level of adhesion is a factor which reduces the microbial load during the postoperative period.

Helicobacter pylori-binding nonacid glycosphingolipids in the human stomach.

Helicobacter pylori has a number of well-characterized carbohydrate-binding adhesins (BabA, SabA, and LabA) that promote adhesion to the gastric mucosa. In contrast, information on the glycoconjugates present in the human stomach remains unavailable. Here, we used MS and binding of carbohydrate-recognizing ligands to characterize the glycosphingolipids of three human stomachs from individuals with different blood group phenotypes (O(Rh-)P, A(Rh+)P, and A(Rh+)p), focusing on compounds recognized by H. pylori We observed a high degree of structural complexity, and the composition of glycosphingolipids differed among individuals with different blood groups. The type 2 chain was the dominating core chain of the complex glycosphingolipids in the human stomach, in contrast to the complex glycosphingolipids in the human small intestine, which have mainly a type 1 core. H. pylori did not bind to the O(Rh-)P stomach glycosphingolipids, whose major complex glycosphingolipids were neolactotetraosylceramide, the Lex, Lea, and H type 2 pentaosylceramides, and the Ley hexaosylceramide. Several H. pylori-binding compounds were present among the A(Rh+)P and A(Rh+)p stomach glycosphingolipids. Ligands for BabA-mediated binding of H. pylori were the Leb hexaosylceramide, the H type 1 pentaosylceramide, and the A type 1/ALeb heptaosylceramide. Additional H. pylori-binding glycosphingolipids recognized by BabA-deficient strains were lactosylceramide, lactotetraosylceramide, the x2 pentaosylceramide, and neolactohexaosylceramide. Our characterization of human gastric receptors required for H. pylori adhesion provides a basis for the development of specific compounds that inhibit the binding of this bacterium to the human gastric mucosa.

Molecular Mechanisms of Leonurus Cardiaca L. Extract Activity in Prevention of Staphylococcal Endocarditis-Study on in Vitro and ex Vivo Models.

Better understanding the mechanisms of Leonurus cardiaca L. extract (LCE) activity is necessary to prepare recommendations for the use of LCE-based herbal products for preventive/supportive purposes in case of infective endocarditis (IE) and other staphylococcal invasive infections. The aim of the study was to analyze molecular mechanisms of LCE effect on Staphylococcus aureus and blood platelets in the context of their interactions playing a pivotal role in such disorders. Using atomic force microscopy, we demonstrated that adhesion forces of S. aureus were markedly reduced after exposure to LCE at subinhibitory concentrations. The effect resulted from the impact of LCE on S. aureus cell morphology and the composition of phospholipids and fatty acids in bacterial membranes (assessed by HPLC), which modulated their stabilization, hydrophobicity, and charge. Moreover, using FACS we showed also that LCE significantly reduced GP IIb/IIIa expression on blood platelets, thus the disruption of platelet-fibrinogen interactions seems to explain antiplatelet effect of LCE. The obtained results prove the usefulness of LCE in the prevention of S. aureus adhesion, platelet activation, and vegetations development, however, also pointed out the necessity of excluding the cationic antibiotics from the treatment of S. aureus-associated IE and other invasive diseases, when motherwort herb is used simultaneously as an addition to the daily diet.

Influence of thickness, color, and polishing process of ethylene-vinyl-acetate sheets on surface roughness and microorganism adhesion.

BACKGROUND/AIM: The surface roughness of dental materials can make cleaning difficult, thus facilitating retention of food debris and accumulation of microorganisms. The aim of this study was to assess whether thickness, color, and the polishing process influence the surface roughness of ethylene-vinyl-acetate (EVA) sheets and the amount of microorganisms that adhere to them. MATERIALS AND METHODS: A total of 180 samples of EVA (5 × 5 mm) were divided into 9 groups according to thickness (G1 = 2 mm; G2 = 3 mm; and G3 = 4 mm), color (G4 = black and G5 = white), and type of polishing (G6 = Scheu™; G7 = Scheu™ associated with hot-air burner; G8 = Erkodent™ and G9 = Erkodent™ associated with hot-air burner). Mean value of 3 roughness parameters was assessed: Ra, Rq, and Rz (one-way ANOVA test and Tukey's test, P < .05). Seven samples of each group (n = 63) were inoculated with saliva for 2 hours to promote microbial adhesion and count the number of colony-forming units (CFUs) (one-way ANOVA test, P < .05). Scanning electron microscopy (SEM) of microbial adhesion and the effects of the polishing process on the surface was assessed. RESULTS: Only the polishing parameter presented less roughness (G2, G7 and G9; P < .05) as also observed on SEM. SEM characterized microbial adhesion but the CFU count was not statistically significant, independent of the assessed parameters. CONCLUSION: The polishing systems, Scheu™ and Erkodent™ in association with a hot-air burner, were effective in decreasing the surface roughness without influencing the amount of adhered microorganisms.

In Vivo Collection and SEM Identification of Oral Biofilm Using Indirect Composite Prototype Restorations. Clinical and Laboratory Study.

BACKGROUND: The oral ecosystem is a dynamic environment inhabited by more than 700 microbial taxa. Recent studies report that multispecies oral biofilms develop on the surface of resin composites leading to degradation of its organic matrix and altered structural stability of the restoration. AIM: To examine the efficacy of a novel clinical approach to investigating in vivo formed biofilms on resin composite surfaces. MATERIALS AND METHODS: The clinical protocol of this study implemented indirect composite molar restorations (from resin material Filtek Z250, 3M ESPE) as intraoral biofilm carriers (test devices). We recruited for the experiment 5 consenting adult subjects with indications for indirect molar restoration. For each subject we fabricated 4 indirect restorations, 3 of which dedicated to different intraoral duration - 3, 7, and 14 days. All composite carriers were fixed temporarily for the intended time period and consecutively replaced. The detached carriers were prepared for microscope analysis at each time interval. The fourth composite carrier was used as the definitive restoration. RESULTS: The timeline of the biofilm formation and the microbial morphology were associated with previous studies of in vivo bacterial colonisation. A correlation between the plaque formation cycle and the DMFt indices of the subjects was established. CONCLUSIONS: The implementation of indirect composite restorations as intraoral biofilm carrier offers valuable contribution to the real time investigation of in vivo biofilm accumulation.

Biosurfactant production by yeasts isolated from hydrocarbon polluted environments.

Thirty-two yeast isolates were retrieved from four soil samples collected from hydrocarbon-polluted locations of Hisar, Haryana, using enrichment culture technique with 1% (v/v) diesel as carbon source. Total nine isolates showing blood agar haemolysis were screened further for biosurfactant production. Yeast isolate, YK32, gave highest 8.4-cm oil displacement which was found to be significantly higher as compared to positive control, 0.2% (w/v) SDS (6.6 cm), followed by 6.2 and 6.0 cm by isolates YK20 and YK21, respectively. Maximum emulsification index was obtained in case of isolates YK20 and YK21 measuring 53.8%, after 6 days of incubation utilizing glucose as carbon source, whereas isolate YK32 was found to be reducing surface tension up to 93 dynes/cm and presented 99.6% degree of hydrophobicity. Olive oil has supported maximum surface tension reduction in isolates YK32 and YK21 equivalent to 53 and 48 dynes/cm and gave 88.3 and 88.5% degree of hydrophobicity, respectively. Diesel was not preferred as carbon source by most of the isolates except YK28 which generated 5.5-cm oil displacement, 25% emulsification index, reduced surface tension to the level of 38 dynes/cm and presented 89% degree of hydrophobicity. Conclusively, isolates YK20, YK21, YK22 and YK32 were marked as promising biosurfactant producers and were subjected to identification. Based on microscopic examination and biochemical peculiarities, isolates YK21 and YK22 might be identified as Candida spp., whereas, isolates YK20 and YK32 might be identified as Saccharomycopsis spp. and Brettanomyces spp., respectively. Interestingly it is the first report indicating Saccharomycopsis spp. and Brettanomyces spp. as a potential biosurfactant producer.

Surface Coating of Gypsum-Based Molds for Maxillofacial Prosthetic Silicone Elastomeric Material: Evaluating Different Microbial Adhesion.

PURPOSE: To compare the adhesion of three microorganisms on modified and unmodified silicone elastomer surfaces with different surface roughnesses and porosities. MATERIALS AND METHODS: Candida albicans, Streptococcus mutans, and Staphylococcus aureus were incubated with modified and unmodified silicone groups (N = 35) for 30 days at 37°C. The counts of viable microorganisms in the accumulating biofilm layer were determined and converted to cfu/cm2 unit surface area. A scanning electron microscope (SEM) was used to evaluate the microbial adhesion. Statistical analysis was performed using t-test, one-way ANOVA, and post hoc tests as indicated. RESULTS: Significant differences in microbial adhesion were observed between modified and unmodified silicone elastomers after the cells were incubated for 30 days (p < 0.001). SEM showed evident differences in microbial adhesion on modified silicone elastomer compared with unmodified silicone elastomer. CONCLUSIONS: Surface modification of silicone elastomer yielding a smoother and less porous surface showed lower adhesion of different microorganisms than observed on unmodified surfaces.

Effect of comonomer of methacrylic acid on flexural strength and adhesion of Staphylococcus aureus to heat polymerized poly (methyl methacrylate) resin: An in vitro study.

AIMS AND OBJECTIVE: The purpose of the present study was to evaluate and compare flexural strength and Staphylococcus aureus adhesion of heat-activated poly (methyl methacrylate [MMA]) resin modified with a comonomer of methacrylic acid (MAA) and MMA monomer. MATERIALS AND METHODS: Comonomer preparation was done with the addition of varying concentration of MAA (0, 15, 20, and 25 wt %) to the MMA of conventional heat-activated denture base resin to prepare the specimens. Prepared specimens were stored in distilled water at 37°C for 1 day and 1 week before the evaluation of flexural strength and microbial adhesion. Flexural strength was measured using a universal testing machine at a crosshead speed for 2 mm/min (n = 10). Microbial adhesion (colony-forming unit [CFU]) was evaluated against S. aureus using a quadrant streaking method (n = 5). Data were subjected to one-way ANOVA, and the significant differences among the results were subjected to Tukey's HSD test. P < 0.05 was considered statistically significant. RESULTS: Addition of MAA to the MMA monomer was found to significantly reduce the adhesion of S. aureus for all the groups. Reduction of CFU of S. aureus was found be more significant for Group 3 as compared to control, both at 1-day (P < 0.001) and 1-week (P < 0.002) storage in distilled water. However, no statistically significant changes in the flexural strength were observed with the addition of MAA at 1-day (P = 0.52) and 1-week (P = 0.88) time interval. CONCLUSION: Addition of MAA to conventional denture base resin reduced the microbial adhesion without significantly affecting the flexural strength.

Long-term effects of CuO nanoparticles on the surface physicochemical properties of biofilms in a sequencing batch biofilm reactor.

In this study, we examined the long-term effects of copper oxide nanoparticles (CuO NPs) on the production and properties of EPS and the resulting variations in surface physicochemical characteristics of biofilms in a sequencing batch biofilm reactor. After exposure to 50 mg/L CuO NPs for 45 days, the protein (PRO) and polysaccharide (PS) contents in loosely bound EPS (LB-EPS) decreased as the production of LB-EPS decreased from 34.4 to 30 mg TOC/g EPS. However, the production of tightly bound EPS (TB-EPS) increased by 16.47 % as the PRO and PS contents increased. The content of humic-like substances (HS) increased significantly, becoming the predominant constituent in EPS with the presence of 50 mg/L CuO NPs. Furthermore, the results of three-dimensional excitation-emission fluorescence spectra confirmed the various changes in terms of the LB-EPS and TB-EPS contents after exposure to CuO NPs. Fourier transform infrared spectroscopy showed that the -OH and -NH2 groups of proteins in EPS were involved in the reaction with CuO NPs. Moreover, the chronic exposure to CuO NPs induced a negative impact on the flocculating efficiency of EPS and on the hydrophobicity and aggregation ability of microbial cells. The PRO/PS ratios of different EPS fractions were consistent with their hydrophobicities (R 2 >0.98) and bioflocculating efficiencies (R 2 >0.95); however, there was no correlation with aggregation ability. Additionally, the presence of bovine serum albumin (BSA) prevented the physical contact between CuO NPs and EPS as a result of NP aggregation and electrostatic repulsion.

Microbial adhesion on novel yttria-stabilized tetragonal zirconia (Y-TZP) implant surfaces with nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) coatings.

OBJECTIVES: Biomaterial surfaces are at high risk for initial microbial colonization, persistence, and concomitant infection. The rationale of this study was to assess the initial adhesion on novel implant surfaces of Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans upon incubation. MATERIALS AND METHODS: The tested samples were 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) samples with nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) coating (A) and 3Y-TZP samples coated with ceria-stabilized zirconia-based (Ce-TZP) composite and a-C:H:N (B). Uncoated 3Y-TZP samples (C) and bovine enamel slabs (BES) served as controls. Once the surface was characterized, the adherent microorganisms were quantified by estimating the colony-forming units (CFUs). Microbial vitality was assessed by live/dead staining, and microbial-biomaterial surface topography was visualized by scanning electron microscopy (SEM). RESULTS: Overall, A and B presented the lowest CFU values for all microorganisms, while C sheltered significantly less E. faecalis, P. aeruginosa, and C. albicans than BES. Compared to the controls, B demonstrated the lowest vitality values for E. coli (54.12 %) and C. albicans (67.99 %). Interestingly, A (29.24 %) exhibited higher eradication rates for S. aureus than B (13.95 %). CONCLUSIONS: Within the limitations of this study, a-C:H:N-coated 3Y-TZP surfaces tended to harbor less initially adherent microorganisms and selectively interfered with their vitality. CLINICAL RELEVANCE: This could enable further investigation of the new multi-functional zirconia surfaces to confirm their favorable antimicrobial properties in vivo.

Effect of metronidazole supplemented with hydroquinone on the adhesion of Lactobacillus acidophilus in ovine vaginal cells.

This work demonstrates that the addition of metronidazole together with a ubiquitous quinone compound reduces adherence of Lactobacillus acidophilus to ovine vaginal cells. Spectrophotometric and voltammetric studies have shown that neoformed compounds were observed in these systems; there were also changes in their electroactive composition, and the oxidant status had a significantly higher value compared to the control (p<0.05). Based on reduction potential (E; mV), the distribution of electroactive compound concentrations suggests that the compounds with low reduction potential induce this behavior, which would indicate that the addition of metronidazole with a ubiquitous quinone compound to the vaginal system might increase the reductive capacity of these systems. This work shows that the study of behavior and fluctuations of the redox compounds that compose the vaginal environment, in terms of concentration and species of redox molecules, must be hierarchized in order to better understand the early stages of colonization by microorganisms.