Biofilm formation and cell viability on monolithic zirconia with silver-doped sodalime glass.

The present study evaluated the effect of glass application with and without silver-doped soda-lime glass on roughness, biofilm formation, cell viability and flexural strength of a zirconia. Samples of 3-YTZP (3 mol% yttria stabilized tetragonal zirconia polycrystals) were divided into: polished (P); glaze (G); glass infiltration (INF); 4% silver-doped soda-lime glass (Ag4); glass infiltration + 4% silver-doped soda-lime glass (INF-Ag4); 5% silver-doped soda-lime glass (Ag5); glass infiltration + 5% silver-doped soda-lime glass (INF-Ag5). Samples were submitted to the following analyses: roughness (Ra); free surface energy (FSE); colony-forming units count (log CFU/mL); scanning electron microscopy (SEM); cytotoxicity (MTT assay) and flexural strength. Ag5 had greater roughness and FSE, but less biofilm adherence. In the CFU, silver-doped soda-lime glass groups inhibited the growth of Candida albicans, while the Ag5 inhibited Streptococcus mutans and none of the groups was effective against Streptococcus sanguinis. In the qualitative evaluation, lower number of colonies in the Ag5 grew up, compared to the control groups (P; G and INF) for both C. albicans and S. mutans. Regarding the MTT assay, the Ag4, INF-Ag4 and INF-Ag5 obtained percentage of cell viability greater than 50%. Ag5 showed lower flexural strength when compared to the control groups, while the application of glass infiltration increased the flexural strength by formation of a graded region between zirconia-glass. In conclusion, Ag5 had the greatest antimicrobial effect, Ag4 and INF-Ag4 were the less cytotoxic and the INF was the most resistant to fracture. Therefore, INF-Ag4 conciliates the best performance in terms of antimicrobial and mechanical properties for a 3-YTZP.

Probiotic Effects of Lactobacillus paracasei 28.4 to Inhibit Streptococcus mutans in a Gellan-Based Formulation.

Streptococcus mutans is considered to be a major bacterium involved in dental caries, and the control of virulence mechanisms is fundamental to prevent disease. Probiotics present a promising preventive method; however, the use of probiotics requires its incorporation into delivery materials to facilitate oral colonization. Thus, we performed a comprehensive study examining preventive effects of Lactobacillus paracasei 28.4-enriched gellan hydrogel materials to inhibit S. mutans in planktonic and biofilm states, addressing its influence in the production of extracellular polysaccharides (EPS) and altered gene expression of several cariogenic virulence factors. L. paracasei 28.4, a strain isolated from the oral cavity of a caries-free individual, was incorporated in three gellan hydrogels (0.5%, 0.75%, and 1% w/v). The pretreatment with probiotic-gellan formulations provided a release of L. paracasei cells over 24 h that was sufficient to inhibit the planktonic growth of S. mutans, independent of the gellan concentrations and pH variations. This pretreatment also had inhibitory activity against S. mutans biofilms, exhibiting a reduction of 0.57 to 1.54 log10 in CFU/mL (p < 0.0001) and a decrease of 68.8 to 71.3% in total biomass (p < 0.0001) compared with the control group. These inhibitory effects were associated with the decreased production of EPS by 80% (p < 0.0001) and the downregulation of luxS, brpA, gbpB, and gtfB genes. The gellan formulation containing L. paracasei 28.4 exhibited probiotic effects for preventing S. mutans growth, biofilm formation, and production of cariogenic factors to suggest possible use in tooth decay prevention.

Anidulafungin liposome nanoparticles exhibit antifungal activity against planktonic and biofilm Candida albicans.

Fungal infections can cause significant patient morbidity and mortality. Nanoparticle therapeutics have the potential to improve treatment of these infections. Here we report the development of liposomal nanoparticles incorporating anidulafungin, a potent antifungal, with the goal of increasing its solubility and aiding in localization to fungi. Liposomes were fabricated with three concentrations of anidulafungin yielding monodisperse ~100 nm unilamellar vesicles. All three formulations inhibited planktonic Candida albicans growth at a minimum inhibitory concentration equivalent to free drug. All three formulations also disrupted preformed C. albicans biofilms, reducing fungal burden by as much as 99%, exhibiting superior biofilm disruption compared with free drug. Liposome formulations tested in vivo in C. albicans infected Galleria mellonella wax moth larvae demonstrated increased survival compared to free drug equivalents, leading to a survival of 33 to 67% of larvae over 7 days depending on the liposome utilized compared with only 25% survival of larvae administered free drug. Liposomal formulations along with free anidulafungin did not cause red blood cell lysis. Ultimately, the liposome formulations reported here increased anidulafungin solubility, displayed promising efficacy against planktonic and biofilm C. albicans, and improved the survival of C. albicans-infected G. mellonella compared to free anidulafungin.

Anti-Candida albicans Activity of Thiazolylhydrazone Derivatives in Invertebrate and Murine Models.

Candidiasis is an opportunistic fungal infection with Candida albicans being the most frequently isolated species. Treatment of these infections is challenging due to resistance that can develop during therapy, and the limited number of available antifungal compounds. Given this situation, the aim of this study was to evaluate the antifungal activity of four thiazolylhydrazone compounds against C. albicans. Thiazolylhydrazone compounds 1, 2, 3, and 4 were found to exert antifungal activity, with MICs of 0.125⁻16.0 µg/mL against C. albicans. The toxicity of the compounds was evaluated using human erythrocytes and yielded LC50 > 64 µg/mL. The compounds were further evaluated using the greater wax moth Galleria mellonella as an in vivo model. The compounds prolonged larval survival when tested between 5 and 15 mg/kg, performing as well as fluconazole. Compound 2 was evaluated in murine models of oral and systemic candidiasis. In the oral model, compound 2 reduced the fungal load on the mouse tongue; and in the systemic model it reduced the fungal burden found in the kidney when tested at 10 mg/kg. These results show that thiazolylhydrazones are an antifungal towards C. albicans with in vivo efficacy.

Temporal Profile of Biofilm Formation, Gene Expression and Virulence Analysis in Candida albicans Strains.

The characterization of Candida albicans strains with different degrees of virulence became very useful to understand the mechanisms of fungal virulence. Then, the objective of this study was to assess and compare the temporal profiles of biofilms formation, gene expression of ALS1, ALS3, HWP1, BCR1, EFG1, TEC1, SAP5, PLB2 and LIP9 and virulence in Galleria mellonella of C. albicans ATCC18804 and a clinical sample isolated from an HIV-positive patient (CA60). Although the CFU/mL counting was higher in biofilms formed in vitro by ATCC strain, the temporal profile of the analysis of the transcripts of the C. albicans strains was elevated to Ca60 compared to strain ATCC, especially in the genes HWP1, ALS3, SAP5, PLB2 and LIP9 (up regulation). Ca60 was more pathogenic for G. mellonella in the survival assay (p = 0.0394) and hemocytes density (p = 0.0349), agreeing with upregulated genes that encode the expression of hyphae and hydrolase genes of Ca60. In conclusion, the C. albicans strains used in this study differ in the amount of biofilm formation, virulence in vivo and transcriptional profiles of genes analyzed that can change factors associated with colonization, proliferation and survival of C. albicans at different niches. SAP5 and HWP1 were the genes more expressed in the formation of biofilm in vitro.

Action of antimicrobial photodynamic therapy on heterotypic biofilm: Candida albicans and Bacillus atrophaeus.

The increase in survival and resistance of microorganisms organized in biofilms demonstrates the need for new studies to develop therapies able to break this barrier, such as photodynamic therapy, which is characterized as an alternative, effective, and non-invasive treatment. The objective was to evaluate in vitro the effect of antimicrobial photodynamic therapy on heterotypic biofilms of Candida albicans and Bacillus atrophaeus using rose bengal (12.5 µM) and light-emitting diode (LED) (532 nm and 16.2 J). We used standard strains of B. atrophaeus (ATCC 9372) and C. albicans (ATCC 18804). The biofilm was formed in the bottom of the plate for 48 h. For the photodynamic therapy (PDT) experimental groups, we added 100 µL of rose bengal with LED (P+L+), 100 µL of rose bengal without LED (P+L-), 100 µL of NaCl 0.9 % solution with LED (P-L+), and a control group without photosensitizer or LED (P-L-). The plates remained in agitation for 5 min (pre-irradiation) and were irradiated with LED for 3 min, and the biofilm was detached using an ultrasonic homogenizer for 30 s. Serial dilutions were plated in BHI agar and HiChrom agar and incubated at 37 °C/48 h. There was a reduction of 33.92 and 29.31 % of colony-forming units per milliliter (CFU/mL) for C. albicans and B. atrophaeus, respectively, from the control group to the group subjected to PDT. However, statistically significant differences were not observed among the P+L+, P+L-, P-L+, and P-L- groups. These results suggest that antimicrobial photodynamic therapy using rose bengal (12.5 µM) with a pre-irradiation period of 5 min and LED for 3 min was not enough to cause a significant reduction in the heterotypic biofilms of C. albicans and B. atrophaeus.