Effect of Chitosan Dispersion and Microparticles on Older Streptococcus mutans Biofilms.

(1) Background: The effectiveness of chitosan to improve the action of antimicrobial compounds against planktonic bacteria and young biofilms has been widely investigated in Dentistry, where the biofilm lifecycle is a determining factor for the success of antibacterial treatment. In the present study, mature Streptococcus mutans biofilms were treated with chitosan dispersion (CD) or chitosan microparticles (CM). (2) Methods: CD at 0.25% and 1% were characterized by texture analysis, while CD at 2% was spray-dried to form CM, which were characterized with respect to particle size distribution, zeta potential, and morphology. After determining the minimum inhibitory and bactericidal concentrations, S. mutans biofilms were grown on glass slides exposed 8×/day to 10% sucrose and 2×/day to CD or CM at 0.25% and 1%. Biofilm viability and acidogenicity were determined, using appropriate control groups for each experiment. (3) Results: CD had high viscosity and CM were spherical, with narrow size distribution and positive zeta potential. CM affected bacterial viability and acidogenicity in mature S. mutans biofilms more strongly than CD, especially at 1%. (4) Conclusions: Both chitosan forms exerted antimicrobial effect against mature S. mutans biofilms. CM at 1% can reduce bacterial viability and acidogenicity more effectively than CD at 1%, and thereby be more effective to control the growth of mature biofilms in vitro.

New perspectives on the topical management of recurrent candidiasis.

Candidiasis is a common opportunistic infection caused by fungi of the Candida genus that affects mainly mucocutaneous tissues (e.g., vaginal, oral, and mammary). This condition has been known for a long time; thus, innumerous topical and systemic treatments are already available on the market worldwide. Yet, recurrent superficial candidiasis (RSC) is an expected outcome, still lacking effective and convenient treatments. Although several individual conditions may contribute to disease recurrence, biofilms' presence seems to be the main etiological factor contributing to antifungal resistance. More than proposing novel antifungal agents, current research seems to be focusing on improving the pharmaceutical technology aspects of formulations to address such a challenge. These include extending and improving intimate contact of drug delivery systems with the mucocutaneous tissues, increasing drug loading dose, and enhancing topical drug permeation. This review discusses the current understanding of the RSC and the use of pharmaceutical technology tools in obtaining better results. Even though several drawbacks of conventional formulations have been circumvented with the help of nano- or microencapsulation techniques and with the use of mucoadhesive formulation excipients, many challenges remain. In particular, the need to mask the unpalatable taste of formulations for the treatment of oral candidiasis, and the necessity of formulations with a "dryer" sensorial feeling and improved performances in providing higher bioavailability for the treatment of mammary and vaginal candidiasis.

Iontophoresis enhances voriconazole antifungal potency and corneal penetration.

Strategies to enhance corneal penetration of voriconazole (VOR) could improve the treatment of fungal keratitis. Here, we evaluated the use of iontophoresis for ocular VOR delivery from either: (i) a cyclodextrin inclusion complex (CD VOR), (ii) a liposome (LP VOR), and (iii) a chitosan-coated liposome (LP VOR CS). LP VOR CS presented mean diameter of 139.2 ±â€¯1.3 nm and zeta potential equal to + 3.3 ±â€¯1.5 mV compared to 134.6 ±â€¯1.7 and -8.2 ±â€¯3.0 mV of LP VOR, which, together with mucin mucoadhesion study, confirmed chitosan-coating. Both drug and liposomal formulations were stable under the influence of an applied electric current. Interestingly, in vitro studies in Candida glabrata culture indicated a decrease in VOR MIC values following iontophoresis (from 0.28 to 0.14 µg/mL). Iontophoresis enhanced drug penetration into the cornea. After 10 min of a 2 mA/cm2 applied current, corneal retained amounts were 45.4 ±â€¯11.2, 30.4 ±â€¯2.1 and 30.6 ±â€¯2.9 µg/cm2 for, respectively, CD VOR, LP VOR, and LP VOR CS. In conclusion, iontophoresis increases drug potency and enhances drug penetration into the cornea, showing potential to be used as "an emergency burst delivery approach".

Effect of an Experimental Formulation Containing Chlorhexidine on Pathogenic Biofilms and Drug Release Behavior in the Presence or Absence of Bacteria.

(1) Background: For any antibacterial oral formulation to be successful, it must present effects in the presence of biofilms. Therefore, our aim is to analyze the drug release and the antibiofilm effects of a semi-solid formulation containing chlorhexidine (CHX) in the presence of pathogenic biofilms. (2) Methods: The biofilms of Streptococcus mutans (n = 6) or Porphyromonas gingivalis (n = 3) were formed for 6 and 4 days, respectively, being exposed to: 1) a CHX system or 2) vehicle control without CHX. A group without treatment was included as negative control. The acidogenicity, CHX quantification and bacterial viability were determined. A dissolution assay in a buffer and culture medium in the absence of bacteria was also performed. (3) Results: Although the CHX quantification in the culture medium of both biofilms was lower compared to the buffer (p < 0.05) and the culture medium in the absence of bacteria, the CHX system was able to display antibiofilm effects until 96 h for the S. mutans biofilms (p < 0.05) and 72 h for the P. gingivalis biofilms (p < 0.05). (4) Conclusions: The experimental formulation is able to extend chlorhexidine effects, even in challenging conditions such as in the presence of bacteria, allowing the in vitro control of cariogenic biofilms for 4 days and periodontopathogenic biofilms for 3 days.

Glucose supplementation effect on the acidogenicity, viability, and extracellular matrix of Candida single- and dual-species biofilms.

AIM: Evidence of glucose supplementation effect on Candida biofilm metabolism has not been demonstrated. Therefore, the aim of the present study was to evaluate the effect of glucose concentration on Candida biofilms. METHODS: Single- and dual-species biofilms of Candida were grown on saliva-coated poly(methyl-methacrylate) disks for 72 hours. Biofilms (N = 8/group) were exposed to the following concentrations of glucose: 100 mmol/L (G100), 300 mmol/L (G300), and no glucose (G0: control). Biofilms were collected to determine the acidogenicity, viability, amount of soluble and insoluble extracellular polysaccharides (IEPS), and surface roughness. Data were analyzed using analysis of variance and Tukey's tests (α < 0.05). RESULTS: Single- and dual-species biofilms from G300 were more acidogenic at 48 and 72 hours compared to G100 and G0 (P < 0.05). The viability of the G100 and G300 groups did not differ (P > 0.05), but differed statistically from G0. The amount of IEPS in the G300 group was statistically higher than the G0 and G100 groups (P < 0.05). The G300 group also presented a higher IEPS proportion per number of viable cells compared to others. G300 presented greater surface roughness for both single- (mean roughness = 1460 µm) and dual-species (mean roughness = 1990 µm) biofilms. CONCLUSIONS: Higher glucose concentration (300 mmol/L) during biofilm development favors the growth of single- and dual-species biofilms of Candida.

Baccharis dracunculifolia-based mouthrinse alters the exopolysaccharide structure in cariogenic biofilms.

Baccharis dracunculifolia is a native plant from Brazil with antimicrobial activity. The purpose of this study was to investigate whether a B. dracunculifolia-based mouthrinse (Bd) changes the structure of insoluble exopolysaccharides (IEPS) in Streptococcus mutans UA159 cariogenic biofilm. Biofilms were grown on glass slides and treated with Bd, its vehicle (VC), chlorhexidine digluconate (CHX), or saline solution (NaCl). Among the treatments, only CHX significantly reduced the biofilm biomass and bacterial viability (p<0.05). Gas chromatography-mass spectrometry and nuclear magnetic resonance analyses revealed that IEPS from the four biofilm samples were α- glucans containing different proportions of (1→6) and (1→3) glycosidic linkages. The structural differences among the four IEPS were compared by principal component analysis (PCA). PCA analysis indicated that IEPS from VC- and NaCl-treated biofilms were structurally similar to each other. Compared with the control, IEPS from Bd- and CHX-treated biofilms were structurally different and had distinct chemical profiles. In summary, the fact that Bd changed the IEPS chemical composition indicates that this mouthrinse may affect the cariogenic properties of the S. mutans biofilm formed.

Adhesion and Initial Colonization of Streptococcus mutans is Influenced by Time and Composition of Different Composites / La Adhesión y la Colonización Inicial de Streptococcus mutans están Asociadas al Tiempo y la Composición de Diferentes Compuestos

ABSTRACT: The aim of this study was to evaluate the adhesion and initial colonization of S. mutans on the surface of novel composite resins during three experimental periods. Biofilms were formed on specimens of Enamel Plus HRI (Hri), FiltekTM Silorane (Si), Tetric EvoCeram® Bulk Fill (Te), KaloreTM (K), and FiltekTM Z250 (Z) (n=4/experimental period). After 4, 8 and 24 hours, the specimens were assessed for bacterial colony forming unit (CFU/mm2) levels and scanned by electron microscopy. All material surfaces showed a similar susceptibility to bacterial adhesion at 4 hours (p>0.05). The amount of microorganisms in the formed biofilms increased at 8 hours for all groups (p<0.05) and decreased at 24 hours only for Te and Z groups (p<0.05). After 24 h, the K group showed higher microorganism counts compared to the other groups. All composite resins evaluated were susceptible to adhesion by streptococci. However, bacteria attachment was not sufficient to maintain S. mutans colonization on Tetric EvoCeram® Bulk Fill and FiltekTM Z250 composites. Composite K presented the highest mean values for bacterial adhesion. Also, it was observed that the composition of resins could interfere with colonization mechanisms.

RESUMEN: El objetivo de este estudio fue evaluar la adhesión y la colonización inicial de S. mutans en la superficie de nuevas resinas compuestas durante tres períodos experimentales. Las biopelículas se formaron en muestras de Enamel Plus HRI (Hri), FiltekTM Silorane (Si), Tetric EvoCeram® Bulk Fill (Te), KaloreTM (K) y FiltekTM Z250 (Z) (n = 4 / período experimental). Después de 4, 8 y 24 horas, las muestras se evaluaron para determinar los niveles de la unidad formadora de colonias bacterianas (UFC / mm2) y se escanearon por microscopía electrónica. Todas las superficies del material mostraron una susceptibilidad similar a la adhesión bacteriana a las 4 horas (p> 0,05). La cantidad de microorganismos en las biopelículas formadas aumentó a las 8 horas para todos los grupos (p <0,05) y disminuyó a las 24 horas solo para los grupos Te y Z (p <0,05). Después de 24 horas, el grupo K mostró mayores recuentos de microorganismos en comparación con los otros grupos. Todas las resinas compuestas evaluadas fueron susceptibles a la adhesión por estreptococos. Sin embargo, la unión de bacterias no fue suficiente para mantener la colonización de S. mutans en los compuestos Tetric EvoCeram® Bulk Fill y FiltekTM Z250. El compuesto K presentó los valores medios más altos para la adhesión bacteriana. Además, se observó que la composición de las resinas podría interferir con los mecanismos de colonización.