Improvement of XTT assay performance for studies involving Candida albicans biofilms

Effect of hydroxyapatite nanoparticles coating of titanium surface on biofilm adhesion: An in vitro study

AIM

To evaluate the adhesion of mono and duospecies biofilm on a commercially available dental implant surface coated with hydroxyapatite nanoparticles (nanoHA).

MATERIAL AND METHODS

Titanium discs were divided into two groups: double acid-etched (AE) and AE coated with nanoHA (NanoHA). Surface characteristics evaluated were morphology, topography, and wettability. Mono and duospecies biofilms of Streptococcus sanguinis (S. sanguinis) and Candida albicans (C. albicans) were formed. Discs were exposed to fetal bovine serum (FBS) to form the pellicle. Biofilm was growth in RPMI1640 medium with 10% FBS and 10% BHI medium for 6 h. Microbial viability was evaluated using colony-forming unit and metabolic activity by a colorimetric assay of the tetrazolium salt XTT. Biofilm architecture and organization were evaluated by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM).

RESULTS

AE surface had more pores, while NanoHA had even nanoHA crystals distribution. Roughness was similar (AE: 0.59 ± 0.07 µm, NanoHA: 0.69 ± 0.18 µm), but wettability was different (AE: Θw= 81.79 ± 8.55°, NanoHA: Θw= 53.26 ± 11.86°; P = 0.01). NanoHA had lower S. sanguinis viability in monospecies biofilm (P = 0.007). Metabolic activity was similar among all biofilms. In SEM both surfaces on C. albicans biofilm show a similar distribution of hyphae in mono and duospecies biofilms. AE surface has more S. sanguinis than the NanoHA surface in the duospecies biofilm. CLSM showed a large proportion of live cells in all groups.

CONCLUSIONS

The nanoHA surface reduced the adhesion of S. sanguinis biofilm but did not alter the adhesion of C. albicans or the biofilm formed by both species.

Photoactivated riboflavin inhibits planktonic and biofilm growth of Candida albicans and non-albicans Candida species

Fungal infections caused by Candida species pose a serious threat to humankind. Antibiotics abuse and the ability of Candida species to form biofilm have escalated the emergence of drug resistance in clinical settings and hence, rendered it more difficult to treat Candida-related diseases. Lethal effects of Candida infection are often due to inefficacy of antimicrobial treatments and failure of host immune response to clear infections. Previous studies have shown that a combination of riboflavin with UVA (riboflavin/UVA) light demonstrate candidacidal activity albeit its mechanism of actions remain elusive. Thus, this study sought to investigate antifungal and antibiofilm properties by combining riboflavin with UVA against Candida albicans and non-albicans Candida species. The MIC20 for the fluconazole and riboflavin/UVA against the Candida species tested was within the range of 0.125-2 μg/mL while the SMIC50 was 32 μg/mL. Present findings indicate that the inhibitory activities exerted by riboflavin/UVA towards planktonic cells are slightly less effective as compared to controls. However, the efficacy of the combination towards Candida species biofilms showed otherwise. Inhibitory effects exerted by riboflavin/UVA towards most of the tested Candida species biofilms points towards a variation in mode of action that could make it an ideal alternative therapeutic for biofilm-related infections.

Supramolecular Self-Associating Amphiphiles Inhibit Biofilm Formation by the Critical Pathogens, Pseudomonas aeruginosa and Candida albicans

In 2019, 4.95 million deaths were directly attributed to antimicrobial-resistant bacterial infections globally. In addition, the mortality associated with fungal infections is estimated at 1.7 million annually, with many of these deaths attributed to species that are no longer susceptible to traditional therapeutic regimes. Herein, we demonstrate the use of a novel class of supramolecular self-associating amphiphilic (SSA) salts as antimicrobial agents against the critical pathogens Pseudomonas aeruginosa and Candida albicans. We also identify preliminary structure-activity relationships for this class of compound that will aid the development of next-generation SSAs demonstrating enhanced antibiofilm activity. To gain insight into the possible mode of action for these agents, a series of microscopy studies were performed, taking advantage of the intrinsic fluorescent nature of benzothiazole-substituted SSAs. Analysis of these data showed that the SSAs interact with the cell surface and that a benzothiazole-containing SSA inhibits hyphal formation by C. albicans.

DNase improves the efficacy of antimicrobial photodynamic therapy in the treatment of candidiasis induced with Candida albicans

The study evaluated the association of DNase I enzyme with antimicrobial photodynamic therapy (aPDT) in the treatment of oral candidiasis in mice infected with fluconazole-susceptible (CaS) and -resistant (CaR) Candida albicans strains. Mice were inoculated with C. albicans, and after the infection had been established, the tongues were exposed to DNase for 5 min, followed by photosensitizer [Photodithazine®(PDZ)] and light (LED), either singly or combined. The treatments were performed for 5 consecutive days. Treatment efficacy was evaluated by assessing the tongues via fungal viable population, clinical evaluation, histopathological and fluorescence microscopy methods immediately after finishing treatments, and 7 days of follow-up. The combination of DNase with PDZ-aPDT reduced the fungal viability in mice tongues immediately after the treatments by around 4.26 and 2.89 log10 for CaS and CaR, respectively (versus animals only inoculated). In the fluorescence microscopy, the polysaccharides produced by C. albicans and fungal cells were less labeled in animals treated with the combination of DNase with PDZ-aPDT, similar to the healthy animals. After 7 days of the treatment, DNase associated with PDZ-aPDT maintained a lower count, but not as pronounced as immediately after the intervention. For both strains, mice treated with the combination of DNase with PDZ-aPDT showed remission of oral lesions and mild inflammatory infiltrate in both periods assessed, while animals treated only with PDZ-aPDT presented partial remission of oral lesions. DNase I enzyme improved the efficacy of photodynamic treatment.

Storage-related stability and antimicrobial efficacy of bottled, neutral-pH Electrolysed Oxidising Water

OBJECTIVES

Denture stomatitis is prevalent in older people and poses serious health risks. Ready-to-use (RTU) neutral-pH Electrolysed Oxidizing Water (EOW) is an effective environmental disinfectant used in residential care settings and geriatric wards. However, the influence of storage on stability and effectiveness for denture disinfection has not been established. This research investigated the storage-related stability and antimicrobial activity of RTU EOW, and its efficacy against Candida albicans biofilms formed on denture resin.

METHODS

The pH, oxidation/reduction potential (mV), available chlorine content (mg/L) and [HOCl] (mM) of RTU EOW (Envirolyte, New Zealand) solutions (n = 22) were measured from bottle opening to 28 days following storage at 4 °C, room temperature (RT) or 37 °C. Staphylococcus aureus and C. albicans cells were incubated in 80% EOW for contact times (CTs) up to 15 min and colony-forming units (cfu) determined. Minimum inhibitory concentrations (MIC90 EOW-HOCl) after CTs up to five minutes were determined for S. aureus and C. albicans reference strains and clinical isolates. C. albicans-denture resin disc biofilms were assessed after a five-minute CT with undiluted EOW by XTT-metabolic activity assay.

RESULTS

[HOCl] remained stable when RTU EOW was stored at 4 °C or RT for five months after manufacture. One-minute CT resulted in log10 cfu reductions of >6 for S. aureus and >5 for C. albicans. Mean MIC90 for five-minute CT was 37 µM (S. aureus) and 54 µM (C. albicans). Undiluted EOW reduced C. albicans biofilm metabolic activity by 86%.

CONCLUSIONS

RTU neutral-pH EOW is stable over five-months storage and is an effective denture disinfectant.

CLINICAL SIGNIFICANCE

The efficacy of the RTU neutral EOW against C. albicans isolates and biofilms formed on denture resin surfaces supports its use as a denture disinfectant and can inform future research to assess its potential for preventing denture-related oral Candida infections in the older population, especially in resource-limited communities.

Does Streptococcus oralis supernatant influence on the proliferation and virulence of Candida albicans?

OBJECTIVE

To evaluate the influence of Streptococcus oralis supernatant on the proliferation and virulence of Candida albicans.

DESIGN

S. oralis supernatant was obtained by filtration of overnight cultures. Single or dual-species cultures of C. albicans and S. oralis were cultivated in both planktonic and biofilm-based models. Planktonic culture growth was measured, and mature biofilms formed on resin disks were collected to measure biofilm metabolic activity, total biomass, and cell counts. Hyphae formation (virulence factor) and biofilm thickness were analyzed by confocal laser scanning microscopy. Data were analyzed by a one-way ANOVA test followed by the Tukey posthoc test (α = 0.05).

RESULTS

We found that S. oralis supernatant did not influence C. albicans proliferation in planktonic cultures. However, biofilms containing S. oralis supernatant showed higher cell metabolism than C. albicans monoculture biofilms and C. albicans-S. oralis dual-culture biofilms (p < 0.05). Though S. oralis supernatants did increase biofilm metabolic activity, they did not affect the total biomass and cell counts of C. albicans (p > 0.05). However, biofilm imaging revealed enhanced C. albicans hyphae formation in biofilms containing S. oralis supernatant compared to C. albicans monoculture biofilms.

CONCLUSIONS

Secreted metabolites in S. oralis supernatant may contribute to C. albicans metabolism and virulence.

Phenotypic and genotypic characterization of virulence markers and antifungal susceptibility of oral Candida species from diabetic and non-diabetic hemodialysis patients

BACKGROUND

Patients with chronic kidney disease undergoing hemodialysis are often colonized by Candida species with high possibility of fungal infections. The purposes of this study were to determine the prevalence of Candida species, evaluate antifungal susceptibility profile, biofilm formation, proteinase and phospholipase activities, and the frequency of virulence genes in the Candida species isolated from the oral mucosa of hemodialysis diabetic (DM) and non-diabetic (non-DM) patients.

METHODS

This study identified several species of Candida isolated from 69 DM and 58 non-DM patients on hemodialysis using phenotypic methods and PCR-RFLP technique. The identification of C. albicans and C. glabrata complex was performed by HWP1 gene and four oligonucleotides (UNI-5.8S, GLA-f, BRA-f, and NIV-f), respectively. Antifungal susceptibility to amphotericin B, fluconazole, itraconazole, voriconazole, and caspofungin was assessed according to CLSI M27-A3/S4. The biomass, metabolic activity of biofilm, proteinase (P_rz), phospholipase (P_z), and molecular study for virulence genes were assessed using crystal violet, XTT assay, agar-based hydrolytic enzyme, and PCR technique, respectively.

RESULTS

Candida prevalence was 44.9% with 47.8% and 41.4% among DM and non-DM patients, respectively (P = .045). The species identified were C. albicans (49.5%), C. glabrata (16.5%), C. tropicalis (12%), C. kefyr (8.8%), C. parapsilosis (6.6%), C. dubliniensis (3.3%), and C. lusitaniae (3.3%). The antifungal susceptibility profile showed that all Candida isolates were sensitive to amphotericin B, itraconazole, voriconazole, and caspofungin whereas fluconazole resistance was observed in 6.3% (MIC ≥ 64 μg/mL) of C. albicans and 6.6% of C. glabrata (MIC ≥ 64 μg/mL). The susceptible- dose-dependent rate was found in 10.5% of C. albicans. The P_rz values of C. albicans ranged from 0.37 to 0.66 for the DM and 0.44-0.73 for the non-DM group (P < 0.05). The non-albicans Candida (NAC) species produced higher degree of biomass and metabolic activity compared to C. albicans (P < 0.05). Furthermore, significant (p < 0.05) correlations were detected between the biofilm formation with P_rz values and fluconazole MICs. The most detected virulence factors were ALS3 and Sap5.

CONCLUSIONS

These results showed the importance of prevalence of NAC species in hemodialysis patients. Investigating antifungal susceptibility profile made a better understanding of the role of virulence markers in the pathogenesis of Candida strains.

Losartan Plays a Fungistatic and Fungicidal Activity Against Candida albicans Biofilms: Drug Repurposing for Localized Candidosis

Candidosis is one of the most frequent opportunistic infections and exhibits variable clinical presentations, including oral localized forms. Drugs affecting the renin-angiotensin system targets inhibit secreted aspartic proteases from Candida albicans. The objective of the study was to evaluate whether losartan has antimicrobial action against C. albicans biofilms. Biofilms were treated with losartan or aliskiren (for comparison) for 24 h. Metabolic activity of viable cells and growth inhibition of C. albicans biofilms were assessed using XTT [2,3-Bis(2-Methoxy-4-Nitro-5-Sulfophenyl)-5-[(Phenyl-Amino)Carbonyl]-2H-Tetrazolium Hydroxide] and colony-forming unit assays, respectively. In addition, the cytotoxicity of the drugs on human cells was evaluated using the AlamarBlue assay. Both drugs decreased fungal viability at all concentrations. In addition, all concentrations of losartan inhibited the growth of C. albicans biofilm, ranging from 47% to 88.5%, whereas aliskiren showed inhibition from 1 to 10 mg/mL, which ranged from 16% to 97.6%. Furthermore, at certain concentrations, these drugs maintained the viability of human cells. Losartan and aliskiren have fungistatic and fungicidal action against C. albicans biofilms and are compatible with human cells. Therefore, these antihypertensive drugs can be repurposed to interfere with the metabolism and development of Candida biofilms, which are widely associated with clinical forms of candidosis, including oral localized forms such as denture stomatitis.

Silver nanoparticles in denture adhesive: An antimicrobial approach against Candida albicans

OBJECTIVE

To evaluate the antimicrobial potential of silver nanoparticles (Ag NPs) synthesized using three different routes (ultraviolet light, Turkevich, and green chemistry method using Glycine max extract) associated with COREGA® denture powder adhesive.

METHODS

Heat-cured acrylic resin specimens were treated with different Ag NPs associated with the adhesive (AD + Ag UV, AD + Ag Turk, and AD + Ag Gm groups). As controls, the specimens were treated with a combination of adhesive and nystatin (AD + Nyst group), only adhesive (AD group), or submerged on the surface of the specimens (PBS group). After the treatments, biofilms of C. albicans developed for 3, 6, and 12 h on the specimen surfaces. The biofilm was quantified using colony-forming units per milliliter, colorimetric assay, and confocal laser scanning microscopy.

RESULTS

Regardless of the period, we observed an inhibition of fungal load and a reduction in metabolic activity and biofilm mass in the resin specimens treated with the combinations AD/Ag NPs, compared to AD and PBS. The antimicrobial action of the AD + Turk and AD + Ag Gm groups was similar than that for the AD + Nyst group in all periods and viability tests, except for the biofilm mass (12 h).

CONCLUSIONS

The COREGA® adhesive with Ag NPs, mainly those synthesized using the Turkevich and Glycine max methods, showed excellent antimicrobial activity against C. albicans biofilms, maintained for up to 12 h.

CLINICAL SIGNIFICANCE

The association of Ag NPs to the adhesive can add preventive or therapeutic effects against denture stomatitis, to this prosthetic material.

Optotracing for live selective fluorescence-based detection of Candida albicans biofilms

Candida albicans is the most common fungal pathogen in humans, implicated in hospital-acquired infections, secondary infections in human immunodeficiency virus (HIV) patients, and is a significant contributor to the global antimicrobial resistance (AMR) burden. Early detection of this pathogen is needed to guide preventative strategies and the selection and development of therapeutic treatments. Fungal biofilms are a unique heterogeneous mix of cell types, extracellular carbohydrates and amyloid aggregates. Perhaps due to the dominance of carbohydrates in fungi, to date, few specific methods are available for the detection of fungal biofilms. Here we present a new optotracing-based method for the detection and analysis of yeast and biofilms based on C. albicans SC5314 as a model. Using commercial extracts of cell wall carbohydrates, we showed the capability of the optotracer EbbaBiolight 680 for detecting chitin and β-glucans. The sensitivity of this tracer to these carbohydrates in their native environment within fungal cells enabled the visualization of both yeast and hyphal forms of the microbe. Analysis of optotracer fluorescence by confocal laser scanning microscopy revealed extensive staining of fungi cell walls as well as the presence of intracellular amyloid aggregates within a subpopulation of cells within the biofilm. Further analysis of the photophysical properties of bound tracers by spectroscopy and spectral imaging revealed polymorphisms between amyloid aggregates within yeast and hyphal cells and enabled their differentiation. With exceptional spatial and temporal resolution, this assay adds a new technique that facilitates future understanding of fungal biofilms and their formation, and enables direct, unbiased diagnostics of these medically relevant biofilms, as well as the development of antifungal strategies.

Using engineered water nanostructures (EWNS) for wound disinfection: Case study of Acinetobacter baumannii inactivation on skin and the inhibition of biofilm formation

Engineered water nanostructures (EWNS) were utilized to deliver a cocktail of nature derived antimicrobials, to assess their efficacy as a solution to the problem of wound infections. The wound related microorganism Acinetobacter baumannii was inoculated on stainless steel and porcine skin and treated with EWNS. EWNS were able to reduce A. baumannii on stainless steel by 4.79 logs in 15 min, and 2 logs in 30 min on porcine skin. The EWNS were able to reduce the strength of A. baumannii biofilm on stainless steel by 87.31% as measured with the XTT assay (P < .001) and 86.27% in cellular counts (P < .001), after two EWNS interventions of 30 min each. Total antimicrobial dose delivered to the surface was 1.42 ng. SEM of biofilms after EWNS treatment showed reduced biomass. These results indicate that the EWNS technology has potential for application in field of wound disinfection and healing.

Influence of β-AgVO3 nanomaterial incorporation on mechanical and microbiological properties of dental porcelain

OBJECTIVE

To explore the effect of adding different percentages of nanostructured silver vanadate decorated with silver nanoparticles (β-AgVO₃) to dental porcelains, evaluating the antimicrobial activity and the influence on the mechanical properties.

METHODS

Thirty-six specimens were made, for each concentration, control group, 0.5%, 1%, 2.5% and 5%, using two commercial brands: IPS InLine and Noritake Cerabien ZR. For the analysis of mechanical properties, the Vickers microhardness test and the roughness test were performed. For the antimicrobial analysis, the XTT and CFU assays were performed.

RESULTS

There was a statistically significant difference between groups for mechanical and microbiological analyses.

SIGNIFICANCE

The modification of dental porcelains, with the incorporation of β-AgVO₃, influenced the mechanical properties of the material and demonstrated antimicrobial activity at certain concentrations.

In vitro effect of farnesol on planktonic cells and dual biofilm formed by Candida albicans and Escherichia coli

Many biofilm studies have focused on axial biofilms, however biofilms in nature and in vivo environment are multi-species. Farnesol is a sesquiterpene alcohol found in many essential oils. This study investigated the in vitro effects of farnesol on planktonic cells and biofilms of Candida albicans and Escherichia coli. The ultrastructural morphology of farnesol treated cells was evaluated by TEM. According to the XTT results, farnesol caused a significant decrease in metabolic activity and scanning electron microscope images confirmed a reduction in the preformed biofilm as a result of farnesol treatment for single species C. albicans and E. coli biofilms. Although farnesol has less effect on dual species biofilm compared to the single species biofilms, its effect on the dual biofilm was found to be stronger than amphotericin B or ampicillin. Further studies are needed to clarify the role of farnesol on fungal-bacterial biofilms.

Strategies to improve the potency of oxazolidinones towards bacterial biofilms

Biofilms are part of the natural lifecycle of bacteria and are known to cause chronic infections that are difficult to treat. Most antibiotics are developed and tested against bacteria in the planktonic state and are ineffective against bacterial biofilms. The oxazolidinones, including the last resort drug linezolid, are one of the main classes of synthetic antibiotics progressed to clinical use in the last 50 years. They have a unique mechanism of action and only develop low levels of resistance in the clinical setting. With the aim of providing insight into strategies to design more potent antibiotic compounds with activity against bacterial biofilms, we review the biofilm activity of clinically approved oxazolidinones and report on structural modifications to oxazolidinones and their delivery systems which lead to enhanced anti‐biofilm activity.

DNase enhances photodynamic therapy against fluconazole-resistant Candida albicans biofilms

OBJECTIVE

This study evaluated the effectiveness of DNase I combined with antimicrobial photodynamic therapy, mediated by Photodithazine^® and light-emitting diode light, against biofilms formed by a fluconazole-resistant Candida albicans strain (ATCC 96901) and two clinical isolates (R14 and R70).

MATERIALS AND METHODS

Biofilms were grown for 48 h and exposed to DNase for 5 min, followed by application of a photosensitizer (P) and light (L), either singly or combined (P+L+, P-L+, P+L-, P-L-, P-L-DNase, P+L+DNase, P+L-DNase, and P-L+DNase; n = 12). Biofilm analysis included quantification of extracellular matrix components (water-soluble and insoluble proteins and polysaccharides, and extracellular DNA), and biomass (total and insoluble), as well as enumeration of colony-forming units. The data were analyzed using three-way analysis of variance with Bonferroni's post-hoc test.

RESULTS

The DNase treatment combined with aPDT showed a reduction of 1.92, 1.65, and 1.29 log₁₀ of cell viability compared with untreated controls for ATCC 96901, R14, and R70 strains, respectively. It also reduced extracellular matrix contents of water-soluble polysaccharides (36.3%) and extracellular DNA (72.3%), as well as insoluble biomass content (43.3%).

CONCLUSION

The three strains showed similar behavior when treated with DNase, and the extracellular matrix components were affected, improving the effectiveness of antimicrobial photodynamic therapy.

Characterization of Aspergillus nidulans Biofilm Formation and Structure and Their Inhibition by Pea Defensin Psd2

Approximately four million people contract fungal infections every year in Brazil, primarily caused by Aspergillus spp. The ability of these fungi to form biofilms in tissues and medical devices complicates treatment and contributes to high rates of morbidity and mortality in immunocompromised patients. Psd2 is a pea defensin of 5.4 kDa that possesses good antifungal activity against planktonic cells of representative pathogenic fungi. Its function depends on interactions with membrane and cell wall lipid components such as glucosylceramide and ergosterol. In the present study, we characterized Aspergillus nidulans biofilm formation and determined the effect of Psd2 on A. nidulans biofilms. After 4 hours, A. nidulans conidia adhered to polystyrene surfaces and formed a robust extracellular matrix-producing biofilm at 24 h, increasing thickness until 48 h Psd2 inhibited A. nidulans biofilm formation in a dose-dependent manner. Most notably, at 10 μM Psd2 inhibited 50% of biofilm viability and biomass and 40% of extracellular matrix production. Psd2 significantly decreased the colonized surface area by the biofilm and changed its level of organization, causing a shortening of length and diameter of hyphae and inhibition of conidiophore formation. This activity against A. nidulans biofilm suggests a potential use of Psd2 as a prototype to design new antifungal agents to prevent biofilm formation by A. nidulans and related species.

Fungicidal Effect of Lemongrass Essential Oil on Candida albicans Biofilm Pre-established on Maxillofacial Silicone Specimens

Aims:

This in-vitro study aimed to evaluate the efficacy of lemongrass (Cymbopogon citratus) essential oil in eradicating Candida albicans biofilm pre-established on the maxillofacial silicone specimens.

Materials and Methods:

Two maxillofacial silicones, namely, MDX4-4210 and Multisil Epithetik, were used for the fabrication of 6 mm diameter disks (n = 21 for each brand of silicone). A 48-h mature C. albicans ATCC 10231 biofilm was pre-established on sterile silicone specimen. These disks were then exposed to various concentrations of lemongrass essential oil ranging from 0.31% to 5% (v/v), 20% (v/v) nystatin, and RPMI-1640 medium for 18–20 h. After exposure, the remaining viable fungal biofilm was examined by the XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide]-reduction assay. All data were analyzed by using a regression coefficient and a post hoc Tukey HSD multiple comparisons test (α = 0.05).

Results:

Different brands of silicone used for fabrication did not significantly affect the formation of mature C. albicans biofilm (P =0.302). A 5% (v/v) lemongrass essential oil significantly eliminated fungal biofilm by approximately 95% (P =0.031). However, less than 50% of the fungal biofilm was eliminated by the tested oil at a concentration as low as 0.31% (v/v). Furthermore, the fungicidal efficacy against C. albicans biofilm of lemongrass essential oil at 2.5% (v/v) was as potent as that of 20% (v/v) nystatin suspension (P = 0.99).

Conclusion:

Lemongrass essential oil expressed fungicidal effect on C. albicans biofilm pre-established on the disks fabricated from different brands of silicone. Additionally, the fungicidal effectiveness of the oil against the mature fungal biofilm was dose-dependent.

Antifungal and antibiofilm efficacy of cinnamaldehyde-loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles against Candida albicans

Biofilm-associated Candida infections threaten public health and show high mortality. The drugs used in treatment are very limited due to reasons such as toxicity, low efficacy, and drug resistance, and new alternatives are needed. The use of natural products of plant origin in the biofilm management draws attention. CA (cinnamaldehyde, cinnamic aldehyde, or 3-phenyl-2-propenal) is an essential oil component that can also inhibit mold growth and mycotoxin production. However, there are some limitations in its use due to its poor solubility and volatility in water. Recently, the combination of natural components and nanoparticle-based drug delivery systems shows positive results. In this study, the effects of PLGA (poly(DL-lactide-co-glycolide)) nanoparticles arrested with CA (CA-PLGA NPs) on C. albicans planktonic and biofilm forms (prebiofilm and postbiofilm) were investigated. According to the results, the amount of active ingredient loaded in CA-PLGA NPs is much lower than the free CA and a strong antifungal effect was obtained even at this rate. Also, the postbiofilm application is more effective than prebiofilm application. PLGA NPs can also be a useful carrier for other essential oils, and their potential in various antifungal, antibiofilm, and biomedical applications should be investigated.

Characterization and Physical and Biological Properties of Tissue Conditioner Incorporated with Carum copticum L

Aim

One of the main problems in dentistry is the injury caused by the long-term application of an ill-fitting denture. The existence of multiple microorganisms along with the susceptibility of the tissue conditioners to colonize them can lead to denture stomatitis. This study is aimed at developing a tissue conditioner incorporated with Carum copticum L. (C. copticum L.) for the effective treatment of these injuries.

Materials and Methods

The Carum copticum L. essential oil composition was determined by gas chromatography-mass (GC-mass) spectrometry. The antimicrobial activity of the essential oil against the standard strains of bacterial and fungal species was determined by broth microdilution methods as suggested by the Clinical and Laboratory Standards Institute (CLSI). The physical and chemical properties of the prepared tissue conditioner were investigated by viscoelasticity, FTIR assays, and the release study performed. Furthermore, the antibiofilm activity of the Carum copticum L. essential oil-loaded tissue conditioner was evaluated by using the XTT reduction assay and scanning electron microscopy (SEM).

Results

The main component of the essential oil is thymol, which possesses high antimicrobial activity. The broth microdilution assay showed that the essential oil has broad activity as the minimum inhibitory concentration was in the range of 32-128 μg mL^-1. The viscoelasticity test showed that the essential oil significantly diminished the viscoelastic modulus on the first day. The FTIR test showed that Carum copticum L. essential oil was preserved as an independent component in the tissue conditioner. The release study showed that the essential oil was released in 3 days following a sustained release and with an ultimate cumulative release of 81%. Finally, the Carum copticum L. essential oil exhibited significant activity in the inhibition of microbial biofilm formation in a dose-dependent manner. Indeed, the lowest and highest amounts of biofilm formation on the tissue conditioner disks are exhibited in the Streptococcus salivarius and Candida albicans by up to 22.4% and 71.4% at the 64 μg mL^-1 concentration of C. copticum L. with a statistically significant difference (P < 0.05).

Conclusion

The obtained results showed that the Carum copticum L. essential oil-loaded tissue conditioner possessed suitable physical, biological, and release properties for use as a novel treatment for denture stomatitis.

Qualitative and quantitative change of the tolerance to liposomal amphotericin B triggered by biofilm maturation in C. parapsilosis

Candida parapsilosis is an emerging opportunistic pathogen present in both clinical and natural environment, with a strong frequency of biofilm forming strains. While the drugs active against biofilm are rare, liposomal amphotericin B is credited with an antibiofilm activity in some opportunistic species of the genus Candida. Using freshly isolated strains from hospital environment, in this paper we could show the prevalence of biofilm forming vs. nonbiofilm forming strains. The former displayed a large variability in terms of biofilm biomass and metabolic activity. Liposomal amphotericin B minimum inhibitory concentration (MIC) of planktonic cells was below the breakpoint, whereas the sessile cells MIC (SMIC) was 1 or 2 orders of magnitude above the planktonic MIC. When the drug was applied to freshly attached cells, that is, biofilm in formation, the MIC (called SDMIC) was even below the MIC value. All resistance metrics (MIC, SMIC, and SDMIC) were quite variable although no correlation could be detected between them and the metrics used to quantify biofilm activity and biomass production. These findings demonstrate that young biofilm cells are even more susceptible than planktonic cells and that early treatments with this drug can be beneficial in cases of prosthesis implantation or especially when there is the necessity of a CVC reimplantation during a sepsis.

Anti-biofilm effect by the combined action of fluconazole and acetylsalicylic acid against species of Candida parapsilosis complex

The Candida parapsilosis complex has been associated with highly refractory infections mainly due to the presence of biofilms. High glucose levels enable the development of this virulence factor which can aggravate the clinical condition of patients with diabetes mellitus, those using parenteral nutrition, with invasive medical device, including others. Combined antifungal therapy, such as azole and cyclooxygenase inhibitors, may be an alternative in such infections since they modulate prostaglandin production favoring the adhesion and development of biofilms. Thus, the present study aimed to evaluate the influence of glucose supplementation in the formation and detection of Candida parapsilosis complex biofilms and to treat them using fluconazole and a cyclooxygenase inhibitor in combination. Protein spectra evaluation allowed the differentiation between species from the complex (score > 2) in our studies. All isolates were able to form active biofilms at different glucose concentrations. In addition, a significant reduction in biofilm formation was observed when fluconazole and acetylsalicylic acid were combined. The ultrastructural analysis presented typical biofilm characteristics by species from the complex. These data support new combined therapies for the treatment of fungal infections, especially with those which are resistant and therapeutic failure is associated with virulence factors.

Increased Staphylococcus aureus Biofilm Formation on Biodegradable Poly(3-Hydroxybutyrate)-Implants Compared with Conventional Orthopedic Implants: An In Vitro Analysis

OBJECTIVE

To compare the biofilm formation on a biodegradable material, poly(3-hydroxybutyrate) (PHB), with that on conventional titanium (Ti) and steel (St) implant material.

METHODS

Pins made of the different materials were incubated in Müller-Hinton broth inoculated with 2 × 10 colony-forming units (CFU)·mL of Staphylococcus aureus for 2 and 7 days and then sonicated for the disruption of the biofilms. CFU were counted to quantify the number of bacteria in the biofilm, and the cell proliferation assay 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H- tetrazolium-5-carboxanilid salt was used to evaluate their metabolic activity. Scanning electron microscopy visualized the structure of the biofilm.

RESULTS

We found a significantly higher metabolic activity and CFU count in the biofilm of PHB pins compared with St and Ti pins (analysis of variance, P < 0.0001). Scanning electron microscopy revealed structured biofilms on PHB pins already after 2 days of incubation, which was not observed on the other tested implants.

CONCLUSION

PHB implants seem to provide an environment that advantages the formation of biofilms of S. aureus, a common pathogen in implant-related infections. The amount of biofilm is higher on PHB implant compared with conventionally used orthopedic titanium and steel implants. To overcome the potential risk of surgical site infections linked to the clinical use of PHB implants, possible modifications of the material, increasing its antibacterial properties, need to be further investigated.

A Bibliometric Analysis of Articles Published in Brazilian Dental Journal over 30 years

This study assessed bibliometric characteristics of all articles published in Brazilian Dental Journal (BDJ) in its 30 years of existence (1990-2019) and factors associated with citation rates. A document search was carried out in Scopus in December, 2019 and information about the articles were exported, including citations. Type of study and main subject in each article were categorized. Number of citations was categorized in tertiles. Logistic regression models were used to assess the association between variables related to articles' characteristics and number of citations. In 30 years, 1705 articles were published and 18507 citations received, with average 57 articles and 334 pages published yearly and 10.9 cites/doc. The most frequent types of study were laboratorial (63%), clinical (18.5%), and case reports (11%); the main subjects were dental materials (21.6%), endodontics (19.3%), and oral pathology/stomatology (13.1%). Most articles had origin in Brazil (90%), followed by USA (4.6%) and UK (1.5%). Aside from BDJ, Journal of Endodontics (3.5%) and International Endodontic Journal (2.2%) were journals that most often cited BDJ. Main origins of citations were Brazil (36.7%), USA (10.6%), and India (9%). Older articles had higher odds to be highly cited (12% increase/year), longer articles had lower odds (9% decrease/page). Narrative reviews and epidemiological studies were associated with more citations and systematic reviews with less citations. In conclusion, BDJ covered many subjects and study types in 30 years, showing increased growth in international audience. The journal may be regarded as one of the leading Brazilian journals in dentistry published in English.

The Contribution of the Brazilian Dental Journal to the Brazilian Scientific Research over 30 Years

The Brazilian Dental Journal (BDJ) was officially launched in 1990, stimulated by the courage and boldness of researchers dedicated to teaching and research in dentistry. The journal was conceived in a worldwide coverage and universal language to allow publication of the results of Brazilian studies, which otherwise would not be accessible to the scientific dental community. In the year we celebrate the thirtieth anniversary of BDJ, this article presents a brief overview of Brazilian dental research and a bibliometric analysis of the articles published in this journal as a contribution to our readers and fellow researchers. The purpose was to identify the mot frequent categories of study, the most published areas of dentistry and BDJ's top 50 most-cited articles in the Scopus and Google Scholar databases. A search was performed on all BDJ online issues published from 1990 to 2019. In this period, BDJ published 1,710 articles. Based on their distribution by category of study, 557 articles were in the basic research/dental materials area, 527 in the basic research/biology area and 280 in the clinical research area. Eight articles were cited more than 100 times in the Scopus database and 266 times in the Google Scholar database. Endodontics was the most published area. This overview of BDJ production over those 30 years allows establishing a profile of the characteristics, impact and trends of the published studies, as well as the journal's contribution to the top 50 most-cited articles in the Scopus and Google Scholar databases.

In vitro characterization of virulence factors among species of the Candida parapsilosis complex

INTRODUCTION

Candida parapsilosis complex species differ from each other with regard to their prevalence and virulence.

METHODS

The hydrolytic enzyme activity, biofilm production, and adhesion to epithelial cells were analyzed in 87 C. parapsilosis complex strains.

RESULTS

Among the studied isolates, 97.7%, 63.2%, and 82.8% exhibited very strong proteinase, esterase, and hemolysin activity, respectively. All the C. parapsilosis complex isolates produced biofilms and presented an average adherence of 96.0 yeasts/100 epithelial cells.

CONCLUSIONS

Our results show that Candida parapsilosis complex isolates showed different levels of enzyme activity, biofilm production, and adhesion to epithelial cells.

Simple Carbohydrate Derivatives Diminish the Formation of Biofilm of the Pathogenic Yeast Candida albicans

The opportunistic human fungal pathogen Candida albicans relies on cell morphological transitions to develop biofilm and invade the host. In the current study, we developed new regulatory molecules, which inhibit the morphological transition of C. albicans from yeast-form cells to cells forming hyphae. These compounds, benzyl α-l-fucopyranoside and benzyl β-d-xylopyranoside, inhibit the hyphae formation and adhesion of C. albicans to a polystyrene surface, resulting in a reduced biofilm formation. The addition of cAMP to cells treated with α-l-fucopyranoside restored the yeast-hyphae switch and the biofilm level to that of the untreated control. In the β-d-xylopyranoside treated cells, the biofilm level was only partially restored by the addition of cAMP, and these cells remained mainly as yeast-form cells.

Nanoemulsion as an Effective Treatment against Human-Pathogenic Fungi

Advances in medicine have resulted in the discovery and implementation of treatments for human disease. While these recent advances have been beneficial, procedures such as solid-organ transplants and cancer treatments have left many patients in an immunocompromised state. Furthermore, the emergence of immunocompromising diseases such as HIV/AIDS or other immunosuppressive medical conditions have opened an opportunity for fungal infections to afflict patients globally. The development of drug resistance in human-pathogenic fungi and the limited array of antifungal drugs has left us in a scenario where we need to develop new therapeutic approaches to treat fungal infections that are less prone to the development of resistance by pathogenic fungi. The significance of our work lies in utilizing a novel nanoemulsion formulation to treat topical fungal infections while minimizing risks of drug resistance development.

Infections triggered by pathogenic fungi cause a serious threat to the public health care system. In particular, an increase of antifungal drug-resistant fungi has resulted in difficulty in treatment. A limited variety of antifungal drugs available to treat patients has left us in a situation where we need to develop new therapeutic approaches that are less prone to development of resistance by pathogenic fungi. In this study, we demonstrate the efficacy of the nanoemulsion NB-201, which utilizes the surfactant benzalkonium chloride, against human-pathogenic fungi. We found that NB-201 exhibited in vitro activity against Candidaalbicans, including both planktonic growth and biofilms. Furthermore, treatments with NB-201 significantly reduced the fungal burden at the infection site and presented an enhanced healing process after subcutaneous infections by multidrug-resistant C. albicans in a murine host system. NB-201 also exhibited in vitro growth inhibition activity against other fungal pathogens, including Cryptococcus spp., Aspergillus fumigatus, and Mucorales. Due to the nature of the activity of this nanoemulsion, there is a minimized chance of drug resistance developing, presenting a novel treatment to control fungal wound or skin infections.

IMPORTANCE Advances in medicine have resulted in the discovery and implementation of treatments for human disease. While these recent advances have been beneficial, procedures such as solid-organ transplants and cancer treatments have left many patients in an immunocompromised state. Furthermore, the emergence of immunocompromising diseases such as HIV/AIDS or other immunosuppressive medical conditions have opened an opportunity for fungal infections to afflict patients globally. The development of drug resistance in human-pathogenic fungi and the limited array of antifungal drugs has left us in a scenario where we need to develop new therapeutic approaches to treat fungal infections that are less prone to the development of resistance by pathogenic fungi. The significance of our work lies in utilizing a novel nanoemulsion formulation to treat topical fungal infections while minimizing risks of drug resistance development.

Antifungal activity and Shore A hardness of a tissue conditioner incorporated with terpinen-4-ol and cinnamaldehyde

PURPOSE

This study investigated the anti-Candida activity and the Shore A hardness of a tissue conditioner (Softone™) modified by incorporation of terpinen-4-ol and cinnamaldehyde.

MATERIAL AND METHODS

Agar diffusion, microdilution, and mechanism of action methods were performed to determine to evaluate the antifungal activity of phytoconstituents. Then, phytoconstituents in varying concentrations were incorporated into the tissue conditioner. The anti-Candida effect of the modified conditioner was evaluated through agar punch well and biofilm formation methods. Shore A hardness of the experimental liners was evaluated after baseline, 24 h, 48 h, 4 days, and 7 days immersion on artificial saliva.

RESULTS

The phytoconstituents incorporated into Softone showed completely inhibited fungal growth in concentrations of 20-40% and did not present significant antifungal activity until their concentrations where higher than 5%. There were differences between non-modified Softone and M5, M10, C10, and T10% (p < 0.05). The groups containing 10-40% of cinnamaldehyde incorporated into Softone were able to completely inhibit the biofilm. Concentrations below 40% of terpinen-4-ol showed unsatisfactory biofilm inhibition. The T40% and C40% groups presented the lowest Shore A hardness values. Hardness values from groups T40% at 7 days (p = 0.476); C40% at 4 days (p = 0.058); and T20% (p = 0.058), C20% (p = 0.205), T30% (p = 0.154), and C30% (p = 0.874) after 48 h did not differ from the control group.

CONCLUSIONS

Cinnamaldehyde incorporated into Softone inhibited Candida biofilm formation at concentrations of 10-40%, being more effective than terpinen-4-ol modification despite of halo inhibition observed by both products.

CLINICAL RELEVANCE

All modifications showed a very similar pattern of hardness being useful for clinical practice.

The use of polyhydroxylated carboxylic acids and lactones to diminish biofilm formation of the pathogenic yeastCandida albicans

The vaginal microbiome of healthy women is a diverse and dynamic system of various microorganisms. Any sudden change in microbe composition can increase the vaginal pH and thus lead to vaginal infections, conditions that affect a large percentage of women each year. The most common fungal strains involved in infections belong to the yeast species Candida albicans. The main virulence factor of C. albicans is the ability to transform from planktonic yeast-form cells into a filamentous form (hyphae or pseudohyphae), with the subsequent formation of biofilm. The hyphal form, constituted by filamentous cells, has the ability to invade tissue and induce inflammation. Our hypothesis is that certain polyhydroxylated carboxylic acids, that may serve as an alternative carbohydrate source and at the same time lower the pH, function as an indicator of a nutrient-rich environment for C. albicans, which favors planktonic cells over hyphae, and thus diminish the formation of biofilm. We have shown that the biofilm formation in C. albicans and other Candida species can be significantly reduced by the addition of glucono-δ-lactone (GDL).

Treatment of Candida albicans with glucono δ-lactone results in less formation of hyphae and diminish biofilm formation.

Activity of coumarin against Candida albicans biofilms

OBJECTIVE

The aim of this study was to investigate the antibiofilm activity of coumarin against Candida albicans.

METHODS

The efficacy of coumarin against biofilm formation and the mature biofilm of C. albicans was quantified by crystal violet (CV) staining and the 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) reduction assay. The effect of coumarin on C. albicans adhesion was assessed on polystyrene plates and by using the cell surface hydrophobicity (CSH) assay. The morphological transition of C. albicans was conducted in two types of hyphae-inducing media at 37°C. The expression of hypha/biofilm-related genes was evaluated using qRT-PCR analysis. A rescue experiment involving addition of exogenous cyclic adenosine monophosphate (cAMP) was performed to investigate the involvement of cAMP in the yeast-to-hyphae transition. A C. albicans-infected Caenorhabditis elegans model was used to test the anti-virulence efficacy of coumarin.

RESULTS

Treatment with coumarin strongly affected the capacity of C. albicans to form biofilm and significantly impaired the preformed mature biofilm. The addition of coumarin notably inhibited C. albicans adhesion, CSH, and filamentation. The expression of some adhesion- and hypha-related genes, including HWP1, HYR1, ECE1, and ALS3, was remarkably down-regulated upon exposure to coumarin. Supplementation with cAMP partly rescued the coumarin-induced defects in hyphal development. Finally, coumarin prolonged survival in C. albicans-infected nematodes.

CONCLUSION

Coumarin inhibited C. albicans biofilm, which was associated with attenuated adhesion and hyphal growth.

A chemical genetic screen reveals a role for proteostasis in capsule and biofilm formation by Cryptococcus neoformans

Pathogenic microorganisms employ specialized virulence factors to cause disease. Biofilm formation and the production of a polysaccharide capsule are two important virulence factors in Cryptococcus neoformans, the fungal pathogen that causes meningoencephalitis. Here, we show that the bipolar disorder drug lithium inhibits formation of both virulence factors by a mechanism involving dysregulation of the ubiquitin/proteasome system. By using a chemical genetics approach and bioinformatic analyses, we describe the cellular landscape affected by lithium treatment. We demonstrate that lithium affects many different pathways in C. neoformans, including the cAMP/protein kinase A, inositol biosynthesis, and ubiquitin/proteasome pathways. By analyzing mutants with defects in the ubiquitin/proteasome system, we uncover a role for proteostasis in both capsule and biofilm formation. Moreover, we demonstrate an additive influence of lithium and the proteasome inhibitor bortezomib in inhibiting capsule production, thus establishing a link between lithium activity and the proteasome system. Finally, we show that the lithium-mimetic drug ebselen potently blocks capsule and biofilm formation, and has additive activity with lithium or bortezomib. In summary, our results illuminate the impact of lithium on C. neoformans, and link dysregulation of the proteasome to capsule and biofilm inhibition in this important fungal pathogen.

Transcriptomics Study on Staphylococcus aureus Biofilm Under Low Concentration of Ampicillin

Staphylococcus aureus is one of the representative foodborne pathogens which forms biofilm. Antibiotics are widely applied in livestock husbandry to maintain animal health and productivity, thus contribute to the dissemination of antimicrobial resistant livestock and human pathogens, and pose a significant public health threat. Effect of antibiotic pressure on S. aureus biofilm formation, as well as the mechanism, remains unclear. In this study, the regulatory mechanism of low concentration of ampicillin on S. aureus biofilm formation was elucidated. The viability and biomass of biofilm with and without 1/4 MIC ampicillin treatment for 8 h were determined by XTT and crystal violet straining assays, respectively. Transcriptomics analysis on ampicillin-induced and non-ampicillin-induced biofilms were performed by RNA-sequencing, differentially expressed genes identification and annotation, GO functional and KEGG pathway enrichment. The viability and biomass of ampicillin-induced biofilm showed dramatical increase compared to the non-ampicillin-induced biofilm. A total of 530 differentially expressed genes (DEGs) with 167 and 363 genes showing up- and down-regulation, respectively, were obtained. Upon GO functional enrichment, 183, 252, and 21 specific GO terms in biological process, molecular function and cellular component were identified, respectively. Eight KEGG pathways including "Microbial metabolism in diverse environments", "S. aureus infection", and "Monobactam biosynthesis" were significantly enriched. In addition, "beta-lactam resistance" pathway was also highly enriched. In ampicillin-induced biofilm, the significant up-regulation of genes encoding multidrug resistance efflux pump AbcA, penicillin binding proteins PBP1, PBP1a/2, and PBP3, and antimicrobial resistance proteins VraF, VraG, Dlt, and Aur indicated the positive response of S. aureus to ampicillin. The up-regulation of genes encoding surface proteins ClfB, IsdA, and SasG and genes (cap5B and cap5C) which promote the adhesion of S. aureus in ampicillin induced biofilm might explain the enhanced biofilm viability and biomass.

Effect of Chloroaluminium phthalocyanine in cationic nanoemulsion on photoinactivation of multispecies biofilm

BACKGROUND

Photosensitizers in nanocarriers have been investigated for antimicrobial Photodynamic Therapy (aPDT). However, most studies are focused against microorganisms in planktonic or monospecies biofilm. Thus, this in vitro study evaluated the effect of aPDT using Chloroaluminium phthalocyanine (ClAlPc) in cationic nanoemulsion (NE) against Candida albicans, Candida glabrata and Streptococcus mutans grown as multispecies biofilm.

METHODS

Standard suspensions of each microorganism were added into wells of a microtiter plate for biofilm growth for 48 h in a candle jar. The biofilms were incubated with ClAlPc in cationic NE at 31.8 μM for 30 min and illuminated with red light fluence of 39.3 J/cm² (P+L+ group). Additional samples were treated only with photosensitizer (P+L-) or red light (P-L+) or neither (P-L-, control group). aPDT efficacy was assessed by colony quantification, biofilm's metabolic activity, total biomass, and confocal microscopy. Data were analyzed by ANOVA/Welch and post-hoc Tukey/Games-Howell tests (α = 0.05).

RESULTS

aPDT (P+L+) reduced the colony count in 1.30 to 2.24 lg₁₀ and the metabolic activity in 53.7% compared with the control group (P-L-). The total biomass showed no statistical difference among the groups. The confocal microscopy analyzes showed uptake of the PS in the biofilm, and dead cells were observed in the biofilm treated with aPDT.

CONCLUSION

aPDT mediated by ClAlPc in cationic NE promoted photoinactivation of the multispecies biofilm, which was confirmed by colony quantification, metabolic activity, and confocal microscopy. However, the total biomass of the biofilm was not affected by the treatment.

Strategies for combating bacterial biofilms: A focus on anti-biofilm agents and their mechanisms of action

Biofilm refers to the complex, sessile communities of microbes found either attached to a surface or buried firmly in an extracellular matrix as aggregates. The biofilm matrix surrounding bacteria makes them tolerant to harsh conditions and resistant to antibacterial treatments. Moreover, the biofilms are responsible for causing a broad range of chronic diseases and due to the emergence of antibiotic resistance in bacteria it has really become difficult to treat them with efficacy. Furthermore, the antibiotics available till date are ineffective for treating these biofilm related infections due to their higher values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), which may result in in-vivo toxicity. Hence, it is critically important to design or screen anti-biofilm molecules that can effectively minimize and eradicate biofilm related infections. In the present article, we have highlighted the mechanism of biofilm formation with reference to different models and various methods used for biofilm detection. A major focus has been put on various anti-biofilm molecules discovered or tested till date which may include herbal active compounds, chelating agents, peptide antibiotics, lantibiotics and synthetic chemical compounds along with their structures, mechanism of action and their respective MICs, MBCs, minimum biofilm inhibitory concentrations (MBICs) as well as the half maximal inhibitory concentration (IC₅₀) values available in the literature so far. Different mode of action of anti biofilm molecules addressed here are inhibition via interference in the quorum sensing pathways, adhesion mechanism, disruption of extracellular DNA, protein, lipopolysaccharides, exopolysaccharides and secondary messengers involved in various signaling pathways. From this study, we conclude that the molecules considered here might be used to treat biofilm-associated infections after significant structural modifications, thereby investigating its effective delivery in the host. It should also be ensured that minimum effective concentration of these molecules must be capable of eradicating biofilm infections with maximum potency without posing any adverse side effects on the host.

Effect of resveratrol and Regrapex-R-forte on Trichosporon cutaneum biofilm

Microorganisms that cause chronic infections exist predominantly as surface-attached stable communities known as biofilms. Microbial cells in biofilms are highly resistant to conventional antibiotics and other forms of antimicrobial treatment; therefore, modern medicine tries to develop new drugs that exhibit anti-biofilm activity. We investigated the influence of a plant polyphenolic compound resveratrol (representative of the stilbene family) on the opportunistic pathogen Trichosporon cutaneum. Besides the influence on the planktonic cells of T. cutaneum, the ability to inhibit biofilm formation and to eradicate mature biofilm was studied. We have tested resveratrol as pure compound, as well as resveratrol in complex plant extract-the commercially available dietary supplement Regrapex-R-forte, which contains the extract of Vitis vinifera grape and extract of Polygonum cuspidatum root. Regrapex-R-forte is rich in stilbenes and other biologically active substances. Light microscopy imaging, confocal microscopy, and crystal violet staining were used to quantify and visualize the biofilm. The metabolic activity of biofilm-forming cells was studied by the tetrazolium salt assay. Amphotericin B had higher activity against planktonic cells; however, resveratrol and Regrapex-R-forte showed anti-biofilm effects, both in inhibition of biofilm formation and in the eradication of mature biofilm. The minimum biofilm eradicating concentration (MBEC₈₀) for Regrapex-R-forte was found to be 2222 mg/L (in which resveratrol concentration is 200 mg/L). These methods demonstrated that Regrapex-R-forte can be employed as an anti-biofilm agent, as it has similar effect as amphotericin B (MBEC₈₀ = 700 mg/L), which is routinely used in clinical practice.

Study of virulence factor of Candida species in oral lesions and its association with potentially malignant and malignant lesions

OBJECTIVE

The aim of this study was to explore the association between malignant and premalignant lesions and the virulence factor profile of Candida spp. recovered from different oral lesions.

DESIGN

Candida spp. isolated from malignant lesions (squamous cell carcinoma, OC, n = 25), atypical lichen planus (AL, n = 11), chronic candidiasis (CC, n = 25), and asymptomatic carriers (WI, n = 15, control strains.) Isolates were identified in chromogenic medium, colony morphology and biochemical tests. The lipolytic and proteinase activity was determined on supplemented agar with olive oil and BSA, respectively. The biofilm formation with XTT reduction assay and cellular surface hydrophobicity (CSH) by water-hydrocarbon method were performed.

RESULTS

All isolates recovered from oral lesions produced the four virulence factors studied with significantly higher levels than in WI isolates. Interestingly, lipolytic activity was absent in WI isolates. The proteolytic activity was similar in AL and OC isolates. OC isolates showed significantly higher CSH values than other clinical isolates. Non-albicans species showed higher biofilm formation than C.albicans (P = 0.03.) There were no significant differences in virulence factors among species. A strong positive correlation was found between proteinase and lipase activity (r = 0.90, P < 0.0001), and between hydrophobicity and biofilm (R = 0.81, P < 0.0001.) CONCLUSIONS: Our results indicate that OC Candida isolates exhibited a significant higher attributes of virulence than other lesions fungus isolates, providing evidence about the association between Candida pathogenicity and lesions severity.

A new approach by optical coherence tomography for elucidating biofilm formation by emergent Candida species

The majority of microorganisms present a community lifestyle, establishing biofilm ecosystems. However, little is known about its formation in emergent Candida species involved in catheter-related infections. Thus, various techniques may be used in the biofilm detection to elucidate structure and clinical impact. In this context, we report the ability of emergent Candida species (Candida haemulonii, C. lusitaniae, C. pelliculosa, C.guilliermondii, C. famata and C. ciferrii) on developing well structured biofilms with cell viability and architecture, using optical coherence tomography (OCT). This new approach was compared with XTT analyses and Scanning Electron Microscopy (SEM). A positive correlation between oxidative activity (XTT) and OCT results (r = 0.8752, p < 0.0001) was observed. SEM images demonstrated cells attachment, multilayer and morphologic characteristics of the biofilm structure. C. lusitaniae was the emergent species which revealed the highest scattering extension length and oxidative metabolism when evaluated by OCT and XTT methods, respectively. Herein, information on C. ciferri biofilm structure were presented for the first time. The OCT results are independently among Candida strains and no species-specific pattern was observed. Our findings strongly contribute for clinical management based on the knowledge of pathogenicity mechanisms involving emergent yeasts.

Pathogenic features and characteristics of food borne pathogens biofilm: Biomass, viability and matrix

Biofilm is a ubiquitous growth pattern of bacterial species survival but is notorious for its threat on public health and food contamination. Extensive studies of the biofilm structure, formation, quantification, quorum sensing system and underlying control strategies have been reported during the past decades. Insightful elucidation of the pathogenic features and characteristic of bacterial biofilm can facilitate in devising appropriate control strategies for biofilm eradication. Therefore, this review mainly summarized the pathogenic features of biofilms from food borne microorganisms, including the biomass (which could be quantified using crystal violet and fluorogenic dye Syto9 assays), viability (which could be determined by tetrazolium salts, fluorescein diacetate, resazurin staining and alamar blue assays) and matrix (which are commonly detected by dimethyl methylene blue and wheat germ agglutinin assays). In addition, three features were further compared with its particular benefits in specific application.

In vitro and in vivo effects of suloctidil on growth and biofilm formation of the opportunistic fungus Candida albicans

As the most frequent fungal pathogen in humans, Candida albicans can develop serious drug resistance because its biofilms are resistant to most antifungal agents; this leads to an urgent need to develop novel antifungals. Here, we evaluated the efficacy of an antithrombotic drug, suloctidil, against C. albicans biofilms in vitro and in vivo. We found that suloctidil is effective to inhibit C. albicans biofilm, with a minimum inhibitory concentration (MIC₈₀) of 4 μg/mL, a biofilm inhibiting concentration (BIC₈₀) of 16 μg/mL and a biofilm eradicating concentration (BEC₈₀) of 64 μg/mL. Furthermore, the concentration-dependent characteristics of suloctidil were shown by its time-kill curves. Scanning electron microscopy images clearly revealed the morphological effects of suloctidil on biofilm. Yeast-to-hyphal form switching is a key virulence factor of C. albicans; therefore, we performed hyphal growth tests and observed that suloctidil inhibited yeast-to-hyphal form switching. This result was consistent with the down-regulation of hypha-specific gene (HWP1, ALS3, and ECE1) expression levels after suloctidil treatment. In vivo, 256 μg/mL of suloctidil significantly reduced fungal counts (P<0.01) compared to that in groups without treatment; the treatment group induced a slight histological reaction, especially when the treatment lasted for 5 days (P<0.01). Taken together, our data suggest that suloctidil is a potential antifungal agent.

Immiscible poly(lactic acid)/poly(ε-caprolactone) for temporary implants: Compatibility and cytotoxicity

This manuscript focuses on the effect of the addition of a low molecular weight triblock copolymer derived from ε-caprolactone and tetrahydrofuran (CT) on the compatibility and cytotoxicity of immiscible poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) blends. Binary and tertiary PLA/PCL blends were prepared by melt mixing in a twin-screw extruder and their morphological, mechanical and thermal behaviors were investigated by scanning electron microscopy (SEM), tensile and Izod impact test, dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). SEM micrographs showed the CT copolymer suppressed the coalescence phenomena and maintained the size of dispersed PCL domains at approximately 0.35µm. Bioresorbable PLA/PCL blends containing 5wt% of CT copolymer exhibited a remarkable increase in ductility and improved toughness at room temperature. Although the CT copolymer increased the interfacial adhesion, the DMA results suggest it also acts as a plasticizer exclusively for the PCL phase. The cell viability evaluated by the XTT assay confirmed PLA/PCL blends compatibilized by CT copolymer exerted no cytotoxic effect.

Dextranase from Arthrobacter oxydans KQ11-1 inhibits biofilm formation by polysaccharide hydrolysis

Dental plaque is a biofilm of water-soluble and water-insoluble polysaccharides, produced primarily by Streptococcus mutans. Dextranase can inhibit biofilm formation. Here, a dextranase gene from the marine microorganism Arthrobacter oxydans KQ11-1 is described, and cloned and expressed using E. coli DH5α competent cells. The recombinant enzyme was then purified and its properties were characterized. The optimal temperature and pH were determined to be 60°C and 6.5, respectively. High-performance liquid chromatography data show that the final hydrolysis products were glucose, maltose, maltotriose, and maltotetraose. Thus, dextranase can inhibit the adhesive ability of S. mutans. The minimum biofilm inhibition and reduction concentrations (MBIC₅₀ and MBRC₅₀) of dextranase were 2 U ml^-1 and 5 U ml^-1, respectively. Scanning electron microscopy and confocal laser scanning microscope (CLSM) observations confirmed that dextranase inhibited biofilm formation and removed previously formed biofilms.

Aspergillus fumigatus DBM 4057 biofilm formation is inhibited by chitosan, in contrast to baicalein and rhamnolipid

The biofilms of filamentous-forming fungi are a novel and still insufficiently understood research topic. We have studied Aspergillus fumigatus, an ubiquitous opportunistic pathogenic fungus, as a representative model for a study of biofilm formation by filamentous fungi and for assessing the potential anti-biofilm activity of natural substances. The activity of antibiotic amphotericin B and selected natural substances: baicalein, chitosan and rhamnolipid was studied. The minimum suspension inhibitory concentrations (MIC) were determined and the biofilm susceptibility was investigated by determining the metabolic activity of sessile cells (XTT assay) and total biofilm biomass (crystal violet staining). Significant time-dependent differences in substances' anti-biofilm activity were observed. Images of A. fumigatus biofilm were obtained by Cellavista automatic light microscope and spinning disc confocal microscopy. Baicalein and rhamnolipid were not found as suitable substances for inhibition of the A. fumigatus biofilm formation, as neither of the substances inhibited the sessile cells metabolic activity or the total biofilm biomass even at tenfold MIC after 48 h. In contrast, chitosan at 10 × MIC (25 µg mL^-1), suppressed the biofilm metabolic activity by 90 % and the total biofilm biomass by 80 % even after 72 h of cultivation. Amphotericin B inhibited only 14 % of total biofilm biomass (crystal violet staining) and 35 % of metabolic activity (XTT assay) of adherent cells under the same conditions. Our results therefore suggest chitosan as potential alternative for treating A. fumigatus biofilm-associated infections.

In vitro Effects of Lemongrass Extract on Candida albicans Biofilms, Human Cells Viability, and Denture Surface

The purpose of this study was to investigate whether immersion of a denture surface in lemongrass extract (LGE) has effects on C. albicans biofilms, human cell viability and denture surface. Minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) were performed for LGE against C. albicans. For biofilm analysis, discs were fabricated using a denture acrylic resin with surface roughness standardization. C. albicans biofilms were developed on saliva-coated discs, and the effects of LGE at MIC, 5XMIC, and 10XMIC were investigated during biofilm formation and after biofilm maturation. Biofilms were investigated for cell counting, metabolic activity, and microscopic analysis. The cytotoxicity of different concentrations of LGE to peripheral blood mononuclear cells (PBMC) was analyzed using MTT. The effects of LGE on acrylic resin were verified by measuring changes in roughness, color and flexural strength after 28 days of immersion. Data were analyzed by ANOVA, followed by a Tukey test at a 5% significance level. The minimal concentration of LGE required to inhibit C. albicans growth was 0.625 mg/mL, while MFC was 2.5 mg/mL. The presence of LGE during biofilm development resulted in a reduction of cell counting (p < 0.05), which made the MIC sufficient to reduce approximately 90% of cells (p < 0.0001). The exposure of LGE after biofilm maturation also had a significant antifungal effect at all concentrations (p < 0.05). When compared to the control group, the exposure of PBMC to LGE at MIC resulted in similar viability (p > 0.05). There were no verified differences in color perception, roughness, or flexural strength after immersion in LGE at MIC compared to the control (p > 0.05). It could be concluded that immersion of the denture surface in LGE was effective in reducing C. albicans biofilms with no deleterious effects on acrylic properties at MIC. MIC was also an effective and safe concentration for use.

Mixed biofilms formed by C. albicans and non-albicans species: a study of microbial interactions

Most Candida infections are related to microbial biofilms often formed by the association of different species. The objective of this study was to evaluate the interactions between Candida albicans and non-albicans species in biofilms formed in vitro. The non-albicans species studied were:Candida tropicalis, Candida glabrata and Candida krusei. Single and mixed biofilms (formed by clinical isolates of C. albicans and non-albicans species) were developed from standardized suspensions of each strain (10(7) cells/mL), on flat-bottom 96-well microtiter plates for 48 hour. These biofilms were analyzed by counting colony-forming units (CFU/mL) in Candida HiChrome agar and by determining cell viability, using the XTT 2,3-bis (2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide colorimetric assay. The results for both the CFU/mL count and the XTT colorimetric assay showed that all the species studied were capable of forming high levels of in vitro biofilm. The number of CFU/mL and the metabolic activity of C. albicans were reduced in mixed biofilms with non-albicans species, as compared with a single C. albicans biofilm. Among the species tested, C. krusei exerted the highest inhibitory action against C. albicans. In conclusion, C. albicans established antagonistic interactions with non-albicans Candida species in mixed biofilms.