Antimicrobial and antibiofilm activities of Casearia sylvestris extracts from distinct Brazilian biomes against Streptococcus mutans and Candida albicans

Seasonal and circadian rhythms of clerodane diterpenes and glycosylated flavonoids in two varieties of Casearia sylvestris Sw. (Salicaceae)

Casearia sylvestris Sw. (Salicaceae) is noted for its morphological and chemical plasticity and pharmacological properties. The present study investigates two of its varieties: C. sylvestris var. sylvestris, predominant in dense and humid forests and ecotones and characterized by clerodane diterpenes; and C. sylvestris var. lingua, mainly found in xeric and open savannah areas and containing phenolic compounds. Despite their comprehensive chemical profiles, the dynamics of clerodane diterpenes and glycosylated flavonoids remain unknown. This study thus aimed to describe seasonal and circadian variations in their content in the leaves of the two varieties. The relative contents of five diterpenes and three glycosylated flavonoids were monitored monthly, every 3 h for 48 h, over 1 year via high-performance liquid chromatography coupled to diode array detection (HPLC-UV-DAD). The differential expression of photosynthetic proteins (Rubisco and photosystem II) was analyzed by Western blotting. The contents of both chemical classes decreased during the reproductive stage, though the prevalence of diterpenes in var. sylvestris and flavonoids in var. lingua remained unchanged; furthermore, even when the plants are grown under the same geographic and environmental conditions, Rubisco expression in var. lingua is twice that of var. sylvestris. In var. lingua, photosystem II proteins are 10 % less expressed. The study reveals the circadian and seasonal fluctuations and, thus, prevalence of the two main compound classes in the examined varieties. The expression of the investigated photosynthetic proteins provides insights into the two varieties, supporting the prevalence of var. lingua in Cerrado areas and var. sylvestris in Atlantic Forest areas.

Biosynthesis of silver nanoparticle using Bacillus licheniformis culture-supernatant for combating pathogenic biofilms

Bacterial biofilms pose a significant threat to healthcare due to their recalcitrance to antibiotics and disinfectants. This study explores the anti-biofilm potential of Bacillus licheniformis cell-free culture supernatant (CFS) and its derived silver nanoparticles (bSNPs) against Staphylococcus aureus and Pseudomonas aeruginosa. The CFS exhibited potent anti-biofilm activity against both bacterial species, even at low concentrations, while devoid of significant bactericidal effects, mitigating resistance risks. Characterization studies revealed the non-proteinaceous nature and thermal stability of the CFS's anti-biofilm agent, suggesting a robust and heat-resistant structure. Green synthesis of bSNPs from CFS resulted in nanoparticles with significant anti-biofilm properties, particularly against P. aeruginosa, indicating differences in susceptibility between the bacterial species. Epifluorescence microscopy confirmed bSNPs' ability to inhibit and partially disrupt biofilm formation without inducing cellular lysis. The study highlights the potential of B. licheniformis CFS and bSNPs as promising biofilm control agents, offering insights into their mechanisms of action and broad-spectrum efficacy. Further research elucidating the underlying molecular mechanisms and identifying specific bioactive compounds is warranted for the translation of these findings into clinically relevant applications for combating biofilm-associated infections.

Machine Learning-Based Virtual Screening of Antibacterial Agents against Methicillin-Susceptible and Resistant Staphylococcus aureus

The application of computer-aided drug discovery (CADD) approaches has enabled the discovery of new antimicrobial therapeutic agents in the past. The high prevalence of methicillin-resistantStaphylococcus aureus(MRSA) strains promoted this pathogen to a high-priority pathogen for drug development. In this sense, modern CADD techniques can be valuable tools for the search for new antimicrobial agents. We employed a combination of a series of machine learning (ML) techniques to select and evaluate potential compounds with antibacterial activity against methicillin-susceptible S. aureus (MSSA) and MRSA strains. In the present study, we describe the antibacterial activity of six compounds against MSSA and MRSA reference (American Type Culture Collection (ATCC)) strains as well as two clinical strains of MRSA. These compounds showed minimal inhibitory concentrations (MIC) in the range from 12.5 to 200 μM against the different bacterial strains evaluated. Our results constitute relevant proven ML-workflow models to distinctively screen for novel MRSA antibiotics.

Potential Applications and Additive Manufacturing Technology-Based Considerations of Mesoporous Silica: A Review

Nanoporous materials are categorized as microporous (pore sizes 0.2-2 nm), mesoporous (pore sizes 2-50 nm), and macroporous (pore sizes 50-1000 nm). Mesoporous silica (MS) has gained a significant interest due to its notable characteristics, including organized pore networks, specific surface areas, and the ability to be integrated in a variety of morphologies. Recently, MS has been widely accepted by range of manufacturer and as drug carrier. Moreover, silica nanoparticles containing mesopores, also known as mesoporous silica nanoparticles (MSNs), have attracted widespread attention in additive manufacturing (AM). AM commonly known as three-dimensional printing is the formalized rapid prototyping (RP) technology. AM techniques, in comparison to conventional methods, aid in reducing the necessity for tooling and allow versatility in product and design customization. There are generally several types of AM processes reported including VAT polymerization (VP), powder bed fusion (PBF), sheet lamination (SL), material extrusion (ME), binder jetting (BJ), direct energy deposition (DED), and material jetting (MJ). Furthermore, AM techniques are utilized in fabrication of various classified fields such as architectural modeling, fuel cell manufacturing, lightweight machines, medical, and fabrication of drug delivery systems. The review concisely elaborates on applications of mesoporous silica as versatile material in fabrication of various AM-based pharmaceutical products with an elaboration on various AM techniques to reduce the knowledge gap.

Effect of Extracts, Fractions, and Isolated Molecules of Casearia sylvestris to Control Streptococcus mutans Cariogenic Biofilm

The effects of extracts, fractions, and molecules of Casearia sylvestris to control the cariogenic biofilm of Streptococcus mutans were evaluated. First, the antimicrobial and antibiofilm (initial and pre-formed biofilms) in prolonged exposure (24 h) models were investigated. Second, formulations (with and without fluoride) were assessed for topical effects (brief exposure) on biofilms. Third, selected treatments were evaluated via bacterium growth inhibition curves associated with gene expression and scanning electron microscopy. In initial biofilms, the ethyl acetate (AcOEt) and ethanolic (EtOH) fractions from Brasília (BRA/DF; 250 µg/mL) and Presidente Venceslau/SP (Water/EtOH 60:40 and Water/EtOH 40:60; 500 µg/mL) reduced ≥6-logs vs. vehicle. Only the molecule Caseargrewiin F (CsF; 125 µg/mL) reduced the viable cell count of pre-formed biofilms (5 logs vs. vehicle). For topical effects, no formulation affected biofilm components. For the growth inhibition assay, CsF yielded a constant recovery of surviving cells (≅3.5 logs) until 24 h (i.e., bacteriostatic), and AcOEt_BRA/DF caused progressive cell death, without cells at 24 h (i.e., bactericidal). CsF and AcOEt_BRA/DF damaged S. mutans cells and influenced the expression of virulence genes. Thus, an effect against biofilms occurred after prolonged exposure due to the bacteriostatic and/or bactericidal capacity of a fraction and a molecule from C. sylvestris.

The Cytotoxic and Inhibitory Effects of Plant Derivatives on Candida albicans Biofilms: A Scoping Review

Candida albicans infections are related to biofilm formation. The increase in antifungal resistance and their adverse effects have led to the search for therapeutic options as plant derivatives. This scoping review aims to identify the current status of in vitro research on the cytotoxicity and inhibitory effects of plant derivatives on C. albicans biofilms. In this study, PRISMA items were followed. After recognition of the inclusion criteria, full texts were read and disagreements were resolved with a third party. A risk of bias assessment was performed, and information was summarized using Microsoft Office Excel. Thirty-nine papers fulfilling the selection criteria were included. The risk of bias analysis identified most of the studies as low risk. Studies evaluated plant derivatives such as extracts, essential oils, terpenes, alkaloids, flavonoids and polyphenols. Some studies evaluated the inhibition of C. albicans biofilm formation, inhibition on preformed biofilms or both. The derivatives at concentrations greater than or equal to those that have an inhibitory effect on C. albicans biofilms, without showing cytotoxicity, include magnoflorin, ellagic acid, myricetin and eucarobustol from Eucalyptus robusta and, as the works in which these derivatives were studied are of good quality, it is desirable to carry out study in other experimental phases, with methodologies that generate comparable information.

Essential Oils of Aromatic Plant Species from the Atlantic Rainforest Exhibit Extensive Chemical Diversity and Antimicrobial Activity

Microbial resistance, caused by the overuse or inadequate application of antibiotics, is a worldwide crisis, increasing the risk of treatment failure and healthcare costs. Plant essential oils (EOs) consist of hydrophobic metabolites with antimicrobial activity. The antimicrobial potential of the chemical diversity of plants from the Atlantic Rainforest remains scarcely characterized. In the current work, we determined the metabolite profile of the EOs from aromatic plants from nine locations and accessed their antimicrobial and biocidal activity by agar diffusion assays, minimum inhibitory concentration, time-kill and cell-component leakage assays. The pharmacokinetic properties of the EO compounds were investigated by in silico tools. More than a hundred metabolites were identified, mainly consisting of sesqui and monoterpenes. Individual plants and botanical families exhibited extensive chemical variations in their EO composition. Probabilistic models demonstrated that qualitative and quantitative differences contribute to chemical diversity, depending on the botanical family. The EOs exhibited antimicrobial biocidal activity against pathogenic bacteria, fungi and multiple predicted pharmacological targets. Our results demonstrate the antimicrobial potential of EOs from rainforest plants, indicate novel macromolecular targets, and contribute to highlighting the chemical diversity of native species.

Strategies for dispersion of cariogenic biofilms: applications and mechanisms

Bacteria residing within biofilms are more resistant to drugs than planktonic bacteria. They can thus play a significant role in the onset of chronic infections. Dispersion of biofilms is a promising avenue for the treatment of biofilm-associated diseases, such as dental caries. In this review, we summarize strategies for dispersion of cariogenic biofilms, including biofilm environment, signaling pathways, biological therapies, and nanovehicle-based adjuvant strategies. The mechanisms behind these strategies have been discussed from the components of oral biofilm. In the future, these strategies may provide great opportunities for the clinical treatment of dental diseases. Graphical Abstract.

In it together: Candida-bacterial oral biofilms and therapeutic strategies

Under natural environmental settings or in the human body, the majority of microorganisms exist in complex polymicrobial biofilms adhered to abiotic and biotic surfaces. These microorganisms exhibit symbiotic, mutualistic, synergistic, or antagonistic relationships with other species during biofilm colonization and development. These polymicrobial interactions are heterogeneous, complex and hard to control, thereby often yielding worse outcomes than monospecies infections. Concerning fungi, Candida spp., in particular, Candida albicans is often detected with various bacterial species in oral biofilms. These Candida-bacterial interactions may induce the transition of C. albicans from commensal to pathobiont or dysbiotic organism. Consequently, Candida-bacterial interactions are largely associated with various oral diseases, including dental caries, denture stomatitis, periodontitis, peri-implantitis, and oral cancer. Given the severity of oral diseases caused by cross-kingdom consortia that develop hard-to-remove and highly drug-resistant biofilms, fundamental research is warranted to strategically develop cost-effective and safe therapies to prevent and treat cross-kingdom interactions and subsequent biofilm development. While studies have shed some light, targeting fungal-involved polymicrobial biofilms has been limited. This mini-review outlines the key features of Candida-bacterial interactions and their impact on various oral diseases. In addition, current knowledge on therapeutic strategies to target Candida-bacterial polymicrobial biofilms is discussed.

Toxic Potential of Cerrado Plants on Different Organisms

Cerrado has many compounds that have been used as biopesticides, herbicides, medicines, and others due to their highly toxic potential. Thus, this review aims to present information about the toxicity of Cerrado plants. For this purpose, a review was performed using PubMed, Science Direct, and Web Of Science databases. After applying exclusion criteria, 187 articles published in the last 20 years were selected and analyzed. Detailed information about the extract preparation, part of the plant used, dose/concentration tested, model system, and employed assay was provided for different toxic activities described in the literature, namely cytotoxic, genotoxic, mutagenic, antibacterial, antifungal, antiviral, insecticidal, antiparasitic, and molluscicidal activities. In addition, the steps to execute research on plant toxicity and the more common methods employed were discussed. This review synthesized and organized the available research on the toxic effects of Cerrado plants, which could contribute to the future design of new environmentally safe products.

Effect of antimicrobial photodynamic therapy with Chlorella and Curcuma extract on Streptococcus mutans biofilms

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) using natural photosensitive agents is an effective method for preventing oral diseases of bacterial origin. The purpose of this study was to evaluate the antimicrobial effect of aPDT, using powdered extracts of Chlorella and Curcuma, on the biofilms of Streptococcus mutans (S. mutans), a bacterium that is known to cause dental caries.

METHODS

Commercially available powdered Chlorella and Curcuma extracts were used as photosensitizers. S. mutans, cultured for 2 days, was inoculated (0.1 ml; 1 × 109 CFU/ml) on the surface of a hydroxyapatite (HA) disc and incubated for 24 h to allow the formation of a biofilm. The HA disc with the S. mutans biofilm was immersed in either Curcuma extract (0.5 mg/ml), Chlorella extract, distilled water (negative control), or Listerine (positive control) for 1 min and then irradiated with an LED (Qraycam; wavelength, 405 nm; energy, 59 mW) for 5 min.

RESULTS

The application of aPDT with Curcuma or Chlorella extract to S. mutans 24-hour biofilms significantly decreased the number of viable cells and the live/dead cell ratio when compared with those in the negative control (distilled water; p < 0.05).

CONCLUSIONS

aPDT using 405 nm light and Chlorella or Curcuma as a photosensitizer has significant antimicrobial effects against S. mutans biofilms. Thus, employing aPDT with natural plant extracts as photosensitizers could be an effective strategy for preventing dental caries but needs to be evaluated in properly controlled clinical trials..

Combinatorial therapy of chitosan hydrogel-based zinc oxide nanocomposite attenuates the virulence of Streptococcus mutans

Background

Biofilm formation is an important causative factor in the expansion of the carious lesions in the enamel. Hence, new approaches to efficient antibacterial agents are highly demanded. This study was conducted to evaluate the antimicrobial-biofilm activity of chitosan hydrogel (CS gel), zinc oxide/ zeolite nanocomposite (ZnONC) either separately or combined together [ZnONC / CS gel (ZnONC-CS)] against Streptococcus mutans biofilm.

Results

MTT assay demonstrated that the ZnONC-CS exhibits a non-cytotoxic effect (> 90% cell viability) toward human gingival fibroblast cells at different dosages (78.1–625 μg/mL) within 72 h. In comparison with CS gel and ZnONC, ZnONC-CS was superior at biofilm formation and metabolic activity reduction by 33 and 45%, respectively; (P < 0.05). The field emission scanning electron microscopy micrographs of the biofilms grown on the enamel slabs were largely in concordance with the quantitative biofilm assay results. Consistent with the reducing effect of ZnONC-CS on biofilm formation, the expression levels of gtfB, gtfC, and ftf significantly decreased.

Conclusions

Taken together, excellent compatibility coupled with an enhanced antimicrobial effect against S. mutans biofilm has equipped ZnONC-CS as a promising candidate for dental biofilm control.

Infraspecific Chemical Variability and Biological Activity of Casearia sylvestris from Different Brazilian Biomes

Casearia sylvestris is an outstanding representative of the Casearia genus. This representability comes from its distinctive chemical profile and pharmacological properties. This species is widespread from North to South America, occurring in all Brazilian biomes. Based on their morphology, 2 varieties are recognized: C. sylvestris var. sylvestris and C. sylvestris var. lingua. Despite the existence of data about their chemical composition, a deeper understanding of the specialized metabolism correlation and variation in respect to environmental factors and its repercussion over their biological activities was still pending. In this study, an UHPLC-DAD-based metabolomics approach was employed for the investigation of the chemical variation of 12 C. sylvestris populations sampled across 4 Brazilian biomes and ecotones. The correlation between infraspecific chemical variability and the cytotoxic and antioxidant activities was achieved by multivariate data analysis. The analyses showed that C. sylvestris var. lingua prevailed at Cerrado areas, and it was correlated with lower cytotoxic activity and high level of glycosylated flavonoids. Among them, narcissin and isorhamnetin-3-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranoside showed good correlation with the antioxidant activity. Conversely, C. sylvestris var. sylvestris prevailed at the Atlantic Forest areas, and it was associated with high cytotoxic activity and high content of clerodane diterpenoids. Different casearins showed good correlation (R2  = 0.3 - 0.70) with the cytotoxic activity. These findings highlighted the great complexity among different C. sylvestris populations, their chemical profile, and the related biological activities. Consequently, it can certainly influence the medicinal properties, as well as the quality and efficacy, of C. sylvestris phytomedicines.

Application of Antibiotics/Antimicrobial Agents on Dental Caries

Dental caries is the most common oral disease. The bacteriological aetiology of dental caries promotes the use of antibiotics or antimicrobial agents to prevent this type of oral infectious disease. Antibiotics have been developed for more than 80 years since Fleming discovered penicillin in 1928, and systemic antibiotics have been used to treat dental caries for a long time. However, new types of antimicrobial agents have been developed to fight against dental caries. The purpose of this review is to focus on the application of systemic antibiotics and other antimicrobial agents with respect to their clinical use to date, including the history of their development, and their side effects, uses, structure types, and molecular mechanisms to promote a better understanding of the importance of microbial interactions in dental plaque and combinational treatments.