Essential Oils, Silver Nanoparticles and Propolis as Alternative Agents Against Fluconazole Resistant Candida albicans, Candida glabrata and Candida krusei Clinical Isolates

Antimicrobial and synergistic effects of lemongrass and geranium essential oils against Streptococcus mutans, Staphylococcus aureus, and Candida spp

BACKGROUND

The oral cavity harbors more than 700 species of bacteria, which play crucial roles in the development of various oral diseases including caries, endodontic infection, periodontal infection, and diverse oral diseases.

AIM

To investigate the antimicrobial action of Cymbopogon Schoenanthus and Pelargonium graveolens essential oils against Streptococcus mutans, Staphylococcus aureus, Candida albicans, Ca. dubliniensis, and Ca. krusei.

METHODS

Minimum microbicidal concentration was determined following Clinical and Laboratory Standards Institute documents. The synergistic antimicrobial activity was evaluated using the Broth microdilution checkerboard method, and the antibiofilm activity was evaluated with the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay. Data were analyzed by one-way analysis of variance followed by the Tukey post-hoc test (P ≤ 0.05).

RESULTS

C. schoenanthus and P. graveolens essential oils were as effective as 0.12% chlorhexidine against S. mutans and St. aureus monotypic biofilms after 24 h. After 24 h P. graveolens essential oil at 0.25% was more effective than the nystatin group, and C. schoenanthus essential oil at 0.25% was as effective as the nystatin group.

CONCLUSION

C. schoenanthus and P. graveolens essential oils are effective against S. mutans, St. aureus, Ca. albicans, Ca. dubliniensis, and Ca. krusei at different concentrations after 5 min and 24 h.

Antileishmanial and Antifungal Activities of Volatile Oils from Cinnamomum Cassia Bark and Schinus Molle Leaves

This study reports on the chemical composition and antileishmanial and anticandidal activities of volatile oils (VOs) of Schinus molle dried leaves (SM), Cinnamomum cassia branch bark (CC) and their blends. Major constituents of SM were spathulenol (26.93 %), β-caryophyllene (19.90 %), and caryophyllene oxide (12.69 %), whereas (E)-cinnamaldehyde (60.11 %), cinnamyl acetate (20.90 %) and cis-2-methoxycinnamic acid (10.37 %) were predominant in CC. SM (IC50=21.45 μg/mL) and CC (IC50=23.27 μg/mL) displayed good activity against L. amazonensis promastigotes, besides having good or moderate activity against nine Candida strains, with Minimum Inhibitory Concentration (MIC) values ranging from 31.25 to 250 μg/mL. While the three SM and CC blends were not more active than the VOs tested individually, they exhibited remarkably high antileishmanial activity, with IC50 values ranging between 3.12 and 7.04 μg/mL, which is very similar to the IC50 of amphotericin B (positive control).

Silver vanadate nanomaterial incorporated into heat-cured resin and coating in printed resin - Antimicrobial activity in two multi-species biofilms and wettability

OBJECTIVES

To incorporate the nanostructured silver vanadate decorated with silver nanoparticles (AgVO3) into denture base materials: heat-cured (HC) and 3D printed (3DP) resins, at concentrations of 2.5 %, 5 %, and 10 %; and to evaluate the antimicrobial activity in two multi-species biofilm: (1) Candida albicans, Candida glabrata, and Streptococcus mutans, (2) Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus, and the wettability.

METHODS

The AgVO3 was added to the HC powder, and printed samples were coated with 3DP with AgVO3 incorporated. After biofilm formation, the antimicrobial activity was evaluated by colony forming units per milliliter (CFU/mL), metabolic activity, and epifluorescence microscopy. Wettability was assessed by the contact angles with water and artificial saliva.

RESULTS

In biofilm (1), HC-5 % and HC-10 % showed activity against S. mutans, HC-10 % against C. glabrata, and HC-10 % and 3DP-10 % had higher CFU/mL of C. albicans. 3DP-5 % had lower metabolic activity than the 3DP control. In biofilm (2), HC-10 % reduced S. aureus and P. aeruginosa, and HC-5 %, 3DP-2.5 %, and 3DP-5 % reduced S. aureus. 3DP incorporated with AgVO3, HC-5 %, and HC-10 % reduced biofilm (2) metabolic activity. 3DP-5 % and 3DP-10 % increased wettability with water and saliva.

CONCLUSION

HC-10 % was effective against C. glabrata, S. mutans, P. aeruginosa, and S. aureus, and HC-5 % reduced S. mutans and S. aureus. For 3DP, 2.5 % and 5 % reduced S. aureus. The incorporation of AgVO3 into both resins reduced the metabolic activity of biofilms but had no effect on C. albicans. The wettability of the 3DP with water and saliva increased with the addition of AgVO3.

CLINICAL SIGNIFICANCE

The incorporation of silver vanadate into the denture base materials provides antimicrobial efficacy and can prevent the aggravation of oral and systemic diseases. The incorporation of nanomaterials into printed resins is challenging and the coating is an alternative to obtain the inner denture base with antimicrobial effect.

Toxicological and chemoprevention studies of Brazilian brown propolis from Araucaria sp

Brazilian brown propolis (BBP) is a natural product derived predominantly from the south region of Brazil, where Araucaria forests are dominant. Despite its potential as a source of bioactive compounds with leishmanicidal, anti-inflammatory, nociceptive, and antimicrobial properties, BBP has not been comprehensively studied compared to green propolis. Therefore, this study aimed to determine the safety and chemopreventive potential of BBP. The cytotoxicity attributed to BBP was assessed using two different assays, while the Salmonella/microsome assay was employed to evaluate mutagenicity. The acute toxicity attributed to BBP was determined using a zebrafish model, while the chemopreventive potential was investigated utilizing Chinese hamster lung (V79) cell lines. Data demonstrated that BBP exerted cytotoxic effects at concentrations greater than or equal to 10 µg/ml and did not exhibit mutagenicity in Salmonella typhimurium strains TA98 and TA100. However, at the highest concentration tested (4000 µg/plate), BBP induced a significant increase in revertant colonies in S. typhimurium TA102 strain. The LC50 equivalent to 8.83 mg/L was obtained in the acute toxicity evaluation in zebrafish. BBP also showed antigenotoxic effect by significantly reducing chromosomal damage induced by the mutagen doxorubicin in V79 cell cultures at a concentration of 2.5 μg/ml. Compared to Brazilian green and red propolis, BBP exhibited greater toxicity. On the other hand, at lower concentrations, BBP displayed chemopreventive potential, which may be associated with the antioxidant capacity of the extract. These findings contribute to a better understanding of the biological properties and potential applications of BBP in treating various diseases.

Lavandula angustifolia Essential Oils as Effective Enhancers of Fluconazole Antifungal Activity against Candida albicans

The increasing prevalence of Candida albicans resistance to commercial antifungal agents in recent decades has prompted modern medicine and veterinary medicine to search for combined treatment options. The aim of the study was to determine the activity of essential oils from different cultivars and morphological parts of the medicinal lavender (Lavandula angustifolia) in combination with fluconazole against Candida albicans ATCC 10231 strain. The effect of the combination of lavender essential oil with fluconazole was tested using the checkerboard method, and the obtained results were interpreted on the basis of fractional inhibitory concentration indices (FICIs). A synergistic interaction was found for all combinations of fluconazole with essential oils isolated both from flowers and leafy stalks of two tested lavender cultivars: 'Blue River' and 'Ellagance Purple'. The observed enhancement effect of fluconazole antifungal activity was significantly stronger in the case of essential oils obtained from flowers and leafy stalks of 'Blue River' cultivar. Analogous studies were performed for linalool, one of the main components of lavender essential oils, and a similar synergistic interaction with fluconazole was found.

Clinical applications of antimicrobial photodynamic therapy in dentistry

Given the emergence of resistant bacterial strains and novel microorganisms that globally threaten human life, moving toward new treatment modalities for microbial infections has become a priority more than ever. Antimicrobial photodynamic therapy (aPDT) has been introduced as a promising and non-invasive local and adjuvant treatment in several oral infectious diseases. Its efficacy for elimination of bacterial, fungal, and viral infections and key pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Candida albicans, and Enterococcus faecalis have been investigated by many invitro and clinical studies. Researchers have also investigated methods of increasing the efficacy of such treatment modalities by amazing developments in the production of natural, nano based, and targeted photosensitizers. As clinical studies have an important role in paving the way towards evidence-based applications in oral infection treatment by this method, the current review aimed to provide an overall view of potential clinical applications in this field and summarize the data of available randomized controlled clinical studies conducted on the applications of aPDT in dentistry and investigate its future horizons in the dental practice. Four databases including PubMed (Medline), Web of Science, Scopus and Embase were searched up to September 2022 to retrieve related clinical studies. There are several clinical studies reporting aPDT as an effective adjunctive treatment modality capable of reducing pathogenic bacterial loads in periodontal and peri-implant, and persistent endodontic infections. Clinical evidence also reveals a therapeutic potential for aPDT in prevention and reduction of cariogenic organisms and treatment of infections with fungal or viral origins, however, the number of randomized clinical studies in these groups are much less. Altogether, various photosensitizers have been used and it is still not possible to recommend specific irradiation parameters due to heterogenicity among studies. Reaching effective clinical protocols and parameters of this treatment is difficult and requires further high quality randomized controlled trials focusing on specific PS and irradiation parameters that have shown to have clinical efficacy and are able to reduce pathogenic bacterial loads with sufficient follow-up periods.

Evaluation of the Sensitivity of Selected Candida Strains to Ozonated Water-An In Vitro Study

(1) Background and Objectives: Oral candidiasis has increased significantly in recent years. Increasingly, we encounter treatment difficulties related to drug resistance. Therefore, it is necessary to search for other therapies such as ozone therapy, which has antimicrobial activity. The aim of this study was to determine the sensitivity of selected Candida strains to ozonated water based on concentration and contact time (2) Methods: The sensitivity of Candida strains to ozonated water with a concentration of 5 µg/mL, 30 µg/mL, and 50 µg/mL was assessed using Mosmann's Tetrazolium Toxicity (MTT) assay. Statistical differences were assessed by the analysis of variance (ANOVA) and the Newman-Keuls post-hoc test. A p-value of ≤0.05 was considered to indicate a statistically significant difference. (3) Results: In all the strains and research trials, the number of viable cells was reduced by ozonated water. The reduction depended on the exposure time and concentration of ozonated water. The highest percentage reduction (34.98%) for the tested samples was obtained for the C. albicans strain after 120 s of exposure at the highest concentration-50 µg/mL. (4) Conclusions: The selected strains of Candida spp. were sensitive to ozonated water at all tested concentrations (5 µg/mL, 30 µg/mL, and 50 µg/mL). The sensitivity of strains to ozonated water increased with concentration and application time. Moreover, the sensitivity of Candida strains to ozonated water is comparable to that of 0.2% chlorhexidine gluconate.

Antifungal Activity of Mexican Propolis on Clinical Isolates of Candida Species

Infections caused by micro-organisms of the genus Candida are becoming a growing health problem worldwide. These fungi are opportunistic commensals that can produce infections—clinically known as candidiasis—in immunocompromised individuals. The indiscriminate use of different anti-fungal treatments has triggered the resistance of Candida species to currently used therapies. In this sense, propolis has been shown to have potent antimicrobial properties and thus can be used as an approach for the inhibition of Candida species. Therefore, this work aims to evaluate the anti-Candida effects of a propolis extract obtained from the north of Mexico on clinical isolates of Candida species. Candida species were specifically identified from oral lesions, and both the qualitative and quantitative anti-Candida effects of the Mexican propolis were evaluated, as well as its inhibitory effect on C. albicans isolate’s germ tube growth and chemical composition. Three Candida species were identified, and our results indicated that the inhibition halos of the propolis ranged from 7.6 to 21.43 mm, while that of the MFC and FC₅₀ ranged from 0.312 to 1.25 and 0.014 to 0.244 mg/mL, respectively. Moreover, the propolis was found to inhibit germ tube formation (IC₅₀ ranging from 0.030 to 1.291 mg/mL). Chemical composition analysis indicated the presence of flavonoids, including pinocembrin, baicalein, pinobanksin chalcone, rhamnetin, and biochanin A, in the Mexican propolis extract. In summary, our work shows that Mexican propolis presents significant anti-Candida effects related to its chemical composition, and also inhibits germ tube growth. Other Candida species virulence factors should be investigated in future research in order to determine the mechanisms associated with antifungal effects against them.

Promising Anti-Biofilm Agents and Phagocytes Enhancers for the Treatment of Candida albicans Biofilm–Associated Infections

Little is known about the interactions among phagocytes and antifungal agents and the antifungal immunomodulatory activities on Candida species biofilms. Here, inhibition of C. albicans biofilms and the interactions among biofilms and phagocytes alone or in combination with essential oils, biological, and chemical agents, or fluconazole were investigated. Biofilm formation by a panel of 28 C. albicans clinical isolates from hospitalized patients, birds, and cattle was tested. The anti-biofilm activities of cinnamon and clove oils, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and Enterococcus faecalis cell-free supernatant (CFS) in comparison with fluconazole were investigated using crystal violet and XTT reduction assays, expression of hypha-specific and hyphal regulator genes, and scanning electron microscopy (SEM) analysis. Of the tested C. albicans isolates, 15 of 28 (53.6%) were biofilm producers. Cinnamon followed by E. faecalis–CFS, SDS, and CTAB was the most effective inhibitors of planktonic C. albicans and biofilms. Fluconazole was an ineffective inhibitor of C. albicans biofilms. Sessile minimal inhibitory concentration (SMIC₅₀) of cinnamon, SDS, CTAB, and E. faecalis–CFS downregulated the hypha-specific and regulator genes, albeit to various extents, when compared with untreated biofilms (P < 0.001). SEM analysis revealed disruption and deformity of three-dimensional structures in cinnamon oil–treated biofilms. C. albicans sessile cells within biofilm were less susceptible to phagocytosis than planktonic cells. The additive effects of phagocytes and the tested antifungals enabled phagocytes to engulf C. albicans cells rapidly in cinnamon, E. faecalis–CFS, or SDS-treated biofilms. No differences in anti-Candida or anti-biofilm eradication activities were detected among the tested isolates. Our findings reinforce the substantial anti-biofilm activity of cinnamon oil, SDS, and E. faecalis–CFS and provide new avenues for the development of novel anti-biofilm immunotherapies or antifungals that could be used prior to or during the management of cases with biofilm-associated infections.

Essential Oils of Melaleuca, Citrus, Cupressus, and Litsea for the Management of Infections Caused by Candida Species: A Systematic Review

Candida is a common agent of infection in humans, which has a wide distribution and is a colonizer fungus of the body, occasionally assuming the role of a pathogen. The type of treatment depends on the site of infection and the clinical condition of the patient. Superficial infections, such as mucosal infections, can be treated with topical medications. So-called alternative therapies have rarely been studied, although the literature records the effectiveness of some treatments, especially as complementary therapy. The aims of this review were to analyze evidence of the anti-Candida inhibitory activity of essential oils of the Citrus, Cupressus, Litsea, and Melaleuca species; in addition to addressing the chemical composition, probable mechanisms of antifungal action and studies of toxicity, cytotoxicity, and genotoxicity were included. The literature from Medline/PubMed, Science Direct, Scopus, Web of Science, and the Brazilian database Periodic Capes was reviewed. Thirty-eight articles were selected, which included two articles on Litsea spp., seven on Cupressus spp., thirteen articles on Citrus spp., and twenty-one articles on Melaleuca spp. In conclusion, this study showed in vitro evidence for the use of essential oils of the plant species evaluated for the treatment of infections caused by different Candida species.

Identification, characterization and evaluation of novel antifungal cyclic peptides from Neobacillus drentensis

Marine microbes secrete exopolymeric substances (EPS), which surrounds the biofilm and inhibits the fungal growth. Elucidation of the structure and function of the extracellular exopolymeric substances is of vital relevance therapeutically. The active compound responsible for bioactivity was purified and characterized using TLC, LC/MS/MS, GC/MS and FT-IR. Bioactivity of the characterized cyclic peptides (CLPs) against azole resistant and susceptible Candida strains were examined for growth and biofilm formation using scanning electron microscopy, flow cytometry, confocal microscopy. In the present study we identified bioactive cyclic peptides from marine isolated Neobacillus drentensis that exhibited promising tensio-active properties and antifungal efficacy against azole resistant and susceptible Candida albicans. The cluster is composed of five CLP isoforms which were sequenced and identified as new peptides with compositional and structural variations in the amino acid sequence and fatty acid chain. In vitro cytotoxic activity of CLPs was tested in human fibroblast normal cells. We have observed that the CLPs repressed the Candida albicans growth and multiplication by inhibiting the biofilm formation and disruption of branching filamentous hyphae. CLPs have been found to arrest the C. albicans cell cycle by a block at G1-S transition followed by apoptotic cell death. The current studies suggest these natural marine derived CLPs function as potential anti-biofilm agents against azole C. albicans resistant strains.

Assembly and antifungal effect of a new fluconazole-carrier nanosystem

Aim: To assemble, characterize and assess the antifungal effects of a new fluconazole (FLZ)-carrier nanosystem. Materials & methods: The nanosystem was prepared by loading FLZ on chitosan (CS)-coated iron oxide nanoparticles (IONPs). Antifungal effects were evaluated on planktonic cells (by minimum inhibitory concentration determination) and on biofilms (by quantification of cultivable cells, total biomass, metabolism and extracellular matrix) of Candida albicans and Candida glabrata. Results: Characterization results ratified the formation of a nanosystem (<320 nm) with FLZ successfully embedded. IONPs-CS-FLZ nanosystem reduced minimum inhibitory concentration values and, in general, showed similar antibiofilm effects compared with FLZ alone. Conclusion: IONPs-CS-FLZ nanosystem was more effective than FLZ mainly in inhibiting Candida planktonic cells. This nanocarrier has potential to fight fungal infections.

Antiviral, Antibacterial, Antifungal, and Antiparasitic Properties of Propolis: A Review

Propolis is a complex phytocompound made from resinous and balsamic material harvested by bees from flowers, branches, pollen, and tree exudates. Humans have used propolis therapeutically for centuries. The aim of this article is to provide comprehensive review of the antiviral, antibacterial, antifungal, and antiparasitic properties of propolis. The mechanisms of action of propolis are discussed. There are two distinct impacts with regards to antimicrobial and anti-parasitic properties of propolis, on the pathogens and on the host. With regards to the pathogens, propolis acts by disrupting the ability of the pathogens to invade the host cells by forming a physical barrier and inhibiting enzymes and proteins needed for invasion into the host cells. Propolis also inhibits the replication process of the pathogens. Moreover, propolis inhibits the metabolic processes of the pathogens by disrupting cellular organelles and components responsible for energy production. With regard to the host, propolis functions as an immunomodulator. It upregulates the innate immunity and modulates the inflammatory signaling pathways. Propolis also helps maintain the host's cellular antioxidant status. More importantly, a small number of human clinical trials have demonstrated the efficacy and the safety of propolis as an adjuvant therapy for pathogenic infections.

Antifungal and anti-biofilm activity of a new Spanish extract of propolis against Candida glabrata

Background

Resistance to traditional antifungal agents is a considerable health problem nowadays, aggravated by infectious processes related to biofilm formation, usually on implantable devices. Therefore, it is necessary to identify new antimicrobial molecules, such as natural products, to develop new therapeutic strategies to prevent and eradicate these infections. One promising product is propolis, a natural resin produced by honeybees with substances from various botanical sources, beeswax and salivary enzymes. The aim of this work was to study the effect of a new Spanish ethanolic extract of propolis (SEEP) on growth, cell surface hydrophobicity, adherence and biofilm formation of Candida glabrata, a yeast capable of achieving high levels of resistance to available anti-fungal agents.

Methods

The antifungal activity of SEEP was evaluated in the planktonic cells of 12 clinical isolates of C. glabrata. The minimum inhibitory concentration (MIC) of propolis was determined by quantifying visible growth inhibition by serial plate dilutions. The minimum fungicide concentration (MFC) was evaluated as the lowest concentration of propolis that produced a 95% decrease in cfu/mL, and is presented as MFC₅₀ and MFC₉₀, which corresponds to the minimum concentrations at which 50 and 90% of the C. glabrata isolates were inhibited, respectively. Influence on cell surface hydrophobicity (CSH) was determined by the method of microbial adhesion to hydrocarbons (MATH). The propolis effect on adhesion and biofilm formation was determined in microtiter plates by measurement of optical density (OD) and metabolic activity (XTT-assay) in the presence of sub-MIC concentrations of SEEP.

Results

SEEP had antifungal capacity against C. glabrata isolates, with a MIC₅₀ of 0.2% (v/v) and an MFC₅₀ of 0.4%, even in azole-resistant strains. SEEP did not have a clear effect on surface hydrophobicity and adhesion, but an inhibitory effect on biofilm formation was observed at subinhibitory concentrations (0.1 and 0.05%) with a significant decrease in biofilm metabolism.

Conclusions

The novel Spanish ethanolic extract of propolis shows antifungal activity against C. glabrata, and decreases biofilm formation. These results suggest its possible use in the control of fungal infections associated with biofilms.

Effects of Propolis on Infectious Diseases of Medical Relevance

Infectious diseases are a significant problem affecting the public health and economic stability of societies all over the world. Treatment is available for most of these diseases; however, many pathogens have developed resistance to drugs, necessitating the development of new therapies with chemical agents, which can have serious side effects and high toxicity. In addition, the severity and aggressiveness of emerging and re-emerging diseases, such as pandemics caused by viral agents, have led to the priority of investigating new therapies to complement the treatment of different infectious diseases. Alternative and complementary medicine is widely used throughout the world due to its low cost and easy access and has been shown to provide a wide repertoire of options for the treatment of various conditions. In this work, we address the relevance of the effects of propolis on the causal pathogens of the main infectious diseases with medical relevance; the existing compiled information shows that propolis has effects on Gram-positive and Gram-negative bacteria, fungi, protozoan parasites and helminths, and viruses; however, challenges remain, such as the assessment of their effects in clinical studies for adequate and safe use.

Efficacy of Toluidine Blue-Mediated Antimicrobial Photodynamic Therapy on Candida spp. A Systematic Review

The effectiveness of antimicrobial photodynamic therapy (aPDT) in the treatment of oral yeast infections was examined many times in recent years. The authors of this review tried to address the question: "Should TBO (toluidine blue ortho)-mediated aPDT be considered a possible alternative treatment for oral candidiasis?". PubMed/Medline and the Cochrane Central Register of Controlled Trials (CEN-TRAL) databases were searched from 1997 up to the 27th of October 2020 using a combination of the following keywords: (Candida OR Candidiasis oral OR Candidosis oral OR denture stomatitis) AND (toluidine blue OR photodynamic therapy OR aPDT OR photodynamic antimicrobial chemotherapy OR PACT OR photodynamic inactivation OR PDI). Animal studies or in vitro studies involving Candida albicans (C. albicans) and/or nonalbicans stain, randomized clinical trials (RCT) involving patients with oral candidiasis or denture stomatitis published solely in English language were included. Candida elimination method in animal, in vitro studies and RCT used was TBO-mediated aPDT. Exactly 393 studies were taken into consideration. Then, after analyzing titles and abstracts of said studies, 361 were excluded. Only 32 studies ended up being selected for in-depth screening, after which 21 of them were included in this study. All studies reported the antifungal effectiveness of aPDT with TBO against C. albicans and non-albicans Candida. In studies conducted with planktonic cells, only one study showed eradication of C. albicans. All others showed partial elimination and only one of them was not statistically significant. Experiments on yeast biofilms, in all cases, showed partial, statistically significant cell growth inhibition and weight reduction (a reduction in the number of cells-mainly hyphae) and the mass of extracellular polymeric substance (EPS). In vivo aPDT mediated by TBO exhibits antifungal effects against oral Candida spp.; however, its clinical effectiveness as a potent therapeutic strategy for oral yeast infections requires further investigation.

Overcoming bacterial resistance to antibiotics: the urgent need – a review

The discovery of antibiotics is considered one of the most crucial breakthroughs in medicine and veterinary science in the 20th century. From the very beginning, this type of drug was used as a ‘miraculous cure’ for every type of infection. In addition to their therapeutic uses, antibiotics were also used for disease prevention and growth promotion in livestock. Though this application was banned in the European Union in 2006, antibiotics are still used in this way in countries all over the world. The unlimited and unregulated use of antibiotics has increased the speed of antibiotic resistance’s spread in different types of organisms. This phenomenon requires searching for new strategies to deal with hard-to-treat infections. The antimicrobial activity of some plant derivatives and animal products has been known since ancient times. At the beginning of this century, even more substances, such as antimicrobial peptides, were considered very promising candidates for becoming new alternatives to commonly used antimicrobials. However, many preclinical and clinical trials ended without positive results. A variety of strategies to fight microbes exist, but we are a long way from approving them as therapies. This review begins with the discovery of antibiotics, covers the modes of action of select antimicrobials, and ends with a literature review of the newest potential alternative approaches to overcoming the drug resistance phenomenon.

Small extracellular vesicles convey the stress-induced adaptive responses of melanoma cells

Exosomes are small extracellular vesicles (sEVs), playing a crucial role in the intercellular communication in physiological as well as pathological processes. Here, we aimed to study whether the melanoma-derived sEV-mediated communication could adapt to microenvironmental stresses. We compared B16F1 cell-derived sEVs released under normal and stress conditions, including cytostatic, heat and oxidative stress. The miRNome and proteome showed substantial differences across the sEV groups and bioinformatics analysis of the obtained data by the Ingenuity Pathway Analysis also revealed significant functional differences. The in silico predicted functional alterations of sEVs were validated by in vitro assays. For instance, melanoma-derived sEVs elicited by oxidative stress increased Ki-67 expression of mesenchymal stem cells (MSCs); cytostatic stress-resulted sEVs facilitated melanoma cell migration; all sEV groups supported microtissue generation of MSC-B16F1 co-cultures in a 3D tumour matrix model. Based on this study, we concluded that (i) molecular patterns of tumour-derived sEVs, dictated by the microenvironmental conditions, resulted in specific response patterns in the recipient cells; (ii) in silico analyses could be useful tools to predict different stress responses; (iii) alteration of the sEV-mediated communication of tumour cells might be a therapy-induced host response, with a potential influence on treatment efficacy.

Clove oil nanoemulsion showed potent inhibitory effect against Candida spp

Increasing resistance to current fungicides is a clinical problem that leads to the need for new treatment strategies. Clove oil (CO) has already been described as having antifungal action. However, it should not be applied directly to the skin as it may be irritating. One option for CO delivery and suitable topical application would be nanoemulsions (NEs). NEs have advantages such as decreased irritant effects and lower dose use. The purpose of this work was the development of NEs containing CO and in vitro evaluation against Candida albicans and Candida glabrata. The NEs were produced by an ultrasonic processor with different proportions of CO and Pluronic^® F-127. In order to determine the best composition and ultrasound amplitude, an experimental design was performed. For the evaluation, droplet size and polydispersity index (PdI) were used. After the stability study, in vitro activity against C. albicans and C. glabrata was evaluated. NEs selected for the stability study, with diameter <40 nm and PdI <0.2, remained stable for 420 d. Activity against Candida spp. was improved when the CO was nanoemulsified, for it possibly leads to a better interaction between the active and the microorganisms, mainly in C. albicans.

Promising Alternative Therapeutics for Oral Candidiasis

:

Candida is the main human fungal pathogen causing infections (candidiasis), mostly in the elderly and immunocompromised hosts. Even though Candida spp. is a member of the oral microbiota in symbiosis, in some circumstances, it can cause microbial imbalance leading to dysbiosis, resulting in oral diseases. Alternative therapies are urgently needed to treat oral candidiasis (usually associated to biofilms), as several antifungal drugs’ activity has been compromised. This has occurred especially due to an increasing occurrence of drugresistant in Candida spp. strains. The overuse of antifungal medications, systemic toxicity, cross-reactivity with other drugs and a presently low number of drug molecules with antifungal activity, have contributed to important clinical limitations.

:

We undertook a structured search of bibliographic databases (PubMed Central, Elsevier’s ScienceDirect, SCOPUS and Springer’s SpringerLink) for peer-reviewed research literature using a focused review in the areas of alternatives to manage oral candidiasis. The keywords used were “candidiasis”, “oral candidiasis”, “biofilm + candida”, “alternative treatment”, “combination therapy + candida” and the reports from the last 10 to 15 years were considered for this review.

:

This review identified several promising new approaches in the treatment of oral candidiasis: combination anti-Candida therapies, denture cleansers, mouth rinses as alternatives for disrupting candidal biofilms, natural compounds (e.g. honey, probiotics, plant extracts and essential oils) and photodynamic therapy.

:

The findings of this review confirm the importance and the urgency of the development of efficacious therapies for oral candidal infections.

The Anti-Staphylococcal Potential of Ethanolic Polish Propolis Extracts

The principal objective of this study was to determine the anti-staphylococcal potential of ethanol extracts of propolis (EEPs). A total of 20 samples of propolis collected from apiaries located in different regions of Poland were used in the study. The two-fold broth microdilution method revealed some important differences in the antimicrobial activity of investigated EEPs. Up to the concentration of 4096 µg/mL no activity was observed against Gram-negative bacteria (E. coli and P. aeruginosa). Staphylococci exhibited much higher susceptibility. The highest efficiency observed for EEP12 and EEP20 (MIC values ranged between 32 and 256 µg/mL). However, the achievement of bactericidal effect usually required higher concentrations. In the case of clinical isolates of S. aureus MBC values for EEP12 and EEP20 ranged from 512 to 1024 µg/mL. The HPLC analysis revealed that these two products contained a higher concentration of flavonoids (flavonols, flavones, and flavanones) compared to other investigated EEPs. In checkerboard test, a synergistic anti-staphylococcal effect was observed for the action of EEP20 in combination with amikacin, kanamycin, gentamycin, tetracycline, and fusidic acid (all these antibiotics inhibit protein synthesis). Moreover, the investigated EEPs effectively eradicated staphylococcal biofilm. The obtained results clearly confirm the high anti-staphylococcal potential of propolis harvested in Polish apiaries.

Potential of Nanoparticles in Combating Candida Infections

Aims:

The aim of this review is to survey the recent progress made in developing the nanoparticles as antifungal agents especially the nano-based formulations being exploited for the management of Candida infections.

Discussion:

In the last few decades, there has been many-fold increase in fungal infections including candidiasis due to the increased number of immunocompromised patients worldwide. The efficacy of available antifungal drugs is limited due to its associated toxicity and drug resistance in clinical strains. The recent advancements in nanobiotechnology have opened a new hope for the development of novel formulations with enhanced therapeutic efficacy, improved drug delivery and low toxicity.

Conclusion:

Metal nanoparticles have shown to possess promising in vitro antifungal activities and could be effectively used for enhanced and targeted delivery of conventionally used drugs. The synergistic interaction between nanoparticles and various antifungal agents have also been reported with enhanced antifungal activity.

Quorum sensing inhibitors as antipathogens: biotechnological applications

The mechanisms through which microbes communicate using signal molecules has inspired a great deal of research. Microbes use this exchange of information, known as quorum sensing (QS), to initiate and perpetuate infectious diseases in eukaryotic organisms, evading the eukaryotic defense system by multiplying and expressing their pathogenicity through QS regulation. The major issue to arise from such networks is increased bacterial resistance to antibiotics, resulting from QS-dependent mediation of the formation of biofilm, the induction of efflux pumps, and the production of antibiotics. QS inhibitors (QSIs) of diverse origins have been shown to act as potential antipathogens. In this review, we focus on the use of QSIs to counter diseases in humans as well as plants and animals of economic importance. We also discuss the challenges encountered in the potential applications of QSIs.

Antimicrobial magnetic nanoparticles based-therapies for controlling infectious diseases

In the last years, the antimicrobial resistance against antibiotics has become a serious health issue, arise as global threat. This has generated a search for new strategies in the progress of new antimicrobial therapies. In this context, different nanosystems with antimicrobial properties have been studied. Specifically, magnetic nanoparticles seem to be very attractive due to their relatively simple synthesis, intrinsic antimicrobial activity, low toxicity and high versatility. Iron oxide NPs (IONPs) was authorized by the World Health Organization for human used in biomedical applications such as in vivo drug delivery systems, magnetic guided therapy and contrast agent for magnetic resonance imaging have been widely documented. Furthermore, the antimicrobial activity of different magnetic nanoparticles has recently been demonstrated. This review elucidates the recent progress of IONPs in drug delivery systems and focuses on the treatment of infectious diseases and target the possible detrimental biological effects and associated safety issues.

Antifungal activity of essential oils against azole-resistant and azole-susceptible vaginal Candida glabrata strains

Candida glabrata is an opportunistic pathogen, associated with endocarditis, meningitis, and disseminated disease, and also with complicated vaginitis. Essential oils derived from aromatic plants are known in traditional medicine as antimicrobial agents and have antifungal properties. The aim of this work was to evaluate whether 12 tested essential oils (tea tree, laurel, anise, basil, bergamot, lavender, mint, oregano, grapefruit, rosemary, winter savory, and ginger) could have a transverse effect on C. glabrata sensitive strains but above all on strains resistant to the three main azole antifungals used (clotrimazole, fluconazole, itraconazole). For this reason, different strains of C. glabrata, vaginal isolated, were characterized (disk diffusion assay, minimal inhibitory concentration) with respect to their response to such antifungals. Electron microscopy analyses were performed to examine cellular damages in depth. Subsequently, we wanted to evaluate the effect of the oils on human cells to estimate their potential cytotoxicity. Oregano and winter savory were the two most effective essential oils, inducing growth inhibition, cell damage of C. glabrata strains (both sensitive and resistant to azole antifungal drugs), and medium–high level of toxicity against human keratinocytes. The results of this work support the research for new alternatives or complementary therapies against vaginal candidiasis.

Antifungal Activity and Synergism with Azoles of Polish Propolis

The aim of our work was to check if one of the products of natural origin, namely honey bee propolis, may be an alternative or supplement to currently used antifungal agents. The activity of 50 ethanolic extracts of propolis (EEPs), harvested in Polish apiaries, was tested on a group of 69 clinical isolates of C. albicans. Most of the EEPs showed satisfactory activity, with minimum fungicidal concentrations (MFC) mainly in the range of 0.08⁻1.25% (v/v). Eradication of biofilm from polystyrene microtitration plates in 50% (MBEC₅₀, Minimum Biofilm Eradication Concentration) required concentrations in the range of 0.04% (v/v) to more than 1.25% (v/v). High activity was also observed in eradication of biofilm formed by C. glabrata and C. krusei on the surfaces of PVC (Polyvinyl Chloride) and silicone catheters. EEPs at subinhibitory concentrations inhibited yeast-to-mycelia morphological transformation of C. albicans in liquid medium and mycelial growth on solid medium. A synergistic effect was observed for the action of EEP in combination with fluconazole (FLU) and voriconazole (VOR) against C. albicans. In the presence of EEP at concentrations as low as 0.02%, the MICs of FLU and VOR were 256 to 32 times lower in comparison to those of the drug alone. Evidence for the fungal cell membrane as the most probable target of EEPs are presented.

Investigation of the Antifungal Activity and Mode of Action of Thymus vulgaris, Citrus limonum, Pelargonium graveolens, Cinnamomum cassia, Ocimum basilicum, and Eugenia caryophyllus Essential Oils

The antimicrobial activity of plant oils and extracts has been recognized for many years. In this study the activity of Thymus vulgaris, Citrus limonum, Pelargonium graveolens, Cinnamomum cassia, Ocimumbasilicum, and Eugenia caryophyllus essential oils (EOs) distributed by Pollena Aroma (Nowy Dwór Mazowiecki, Poland) was investigated against a group of 183 clinical isolates of C. albicans and 76 isolates of C. glabrata. All of the oils exhibited both fungistatic and fungicidal activity toward C. albicans and C. glabrata isolates. The highest activity was observed for cinnamon oil, with MIC (Minimum Inhibitory Concentration) values in the range 0.002⁻0.125% (v/v). The MIC values of the rest of the oils were in the range 0.005% (or less) to 2.5% (v/v). In most cases MFC (Minimum Fungicidal Concentration) values were equal to MIC or twice as high. Additionally, we examined the mode of action of selected EOs. The effect on cell wall components could not be clearly proved. Three of the tested EOs (thyme, lemon, and clove) affected cell membranes. At the same time, thyme, cinnamon, and clove oil influenced potassium ion efflux, which was not seen in the case of lemon oil. All of the tested oils demonstrated the ability to inhibit the transition of yeast to mycelium form, but the effect was the lowest in the case of cinnamon oil.

Lactoferrin, chitosan and Melaleuca alternifolia-natural products that show promise in candidiasis treatment

The evolution of microorganisms resistant to many medicines has become a major challenge for the scientific community around the world. Motivated by the gravity of such a situation, the World Health Organization released a report in 2014 with the aim of providing updated information on this critical scenario. Among the most worrying microorganisms, species from the genus Candida have exhibited a high rate of resistance to antifungal drugs. Therefore, the objective of this review is to show that the use of natural products (extracts or isolated biomolecules), along with conventional antifungal therapy, can be a very promising strategy to overcome microbial multiresistance. Some promising alternatives are essential oils of Melaleuca alternifolia (mainly composed of terpinen-4-ol, a type of monoterpene), lactoferrin (a peptide isolated from milk) and chitosan (a copolymer from chitin). Such products have great potential to increase antifungal therapy efficacy, mitigate side effects and provide a wide range of action in antifungal therapy.

Essential oils as potential anti-staphylococcal agents

Antibiotic therapy of staphylococcal mastitis is characterized by significantly lower cure rates compared to infections caused by other microorganisms. Thus, it is necessary to search for new, alternative, non-antibiotic agents that are effective in the eradication of these bacteria. The aim of our research was to investigate the antimicrobial, especially anti-staphylococcal potential of a large collection (n=36) of essential oils (EOs). Investigation of the antimicrobial activity of tested oils was determined by using a serial, twofold dilution method in 96-wells microtiter plates under conditions recommended by the Clinical and Laboratory Standards Institute (CLSI). The preliminary analysis revealed that six oils, namely: Manuka, Thyme, Geranium, Cedar, Cinnamon (from bark) and Patchouli exhibited the highest activity against reference strains of bacteria. Significant anti-staphylococcal potential of these oils has been also confirmed for a group of 18 Staphylococcus aureus, 8 Staphylococcus epidermidis and 5 Staphylococcus xylosus strains isolated from cases of bovine mastitis. Especially high activity was observed for Cedar, Patchouli, Thyme and Manuka oils. The MIC (Minimal Inhibitory Concentration) values for Patchouli oil were in the concentrations range of 0.01 to 0.313% (v/v). The three other oils inhibited the growth of staphylococci isolated from mastitis in the concentrations range of 0.01 to 0.625% (v/v). Oils isolated from Cinnamomum cassia and Pelargonium graveolens revealed a bit lower, but still satisfactory activity (MIC values in the concentrations range of 0.02 to 1.25% (v/v) and from 0.078 to 1.25% (v/v), respectively). In many cases a slightly higher concentration of oils was required to obtain the bactericidal effect in comparison to growth inhibition. The time – kill kinetic assay revealed that the bactericidal effect was achieved after two hours incubation of the reference strain S. aureus PCM 2051 cells with Thyme oil at concentration equal to 2xMIC (1.25% (v/v)) or MIC (0.625% (v/v)). A slightly lower activity was observed in the case of Cinnamon oil, the bactericidal effect was achieved after 8 hours of incubation. The results of our research clearly indicate that some essential oils exhibit a promising antimicrobial activity and can be considered as alternative antistaphylococcal agents.

Biosynthesis of silver nanoparticles using Caesalpinia ferrea (Tul.) Martius extract: physicochemical characterization, antifungal activity and cytotoxicity

BACKGROUND

Green synthesis is an ecological technique for the production of well characterized metallic nanoparticles using plants. This study investigated the synthesis of silver nanoparticles (AgNPs) using a Caesalpinia ferrea seed extract as a reducing agent.

METHODS

The formation of AgNPs was identified by instrumental analysis, including ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) of the AgNPs, and surface-enhanced Raman scattering (SERS) spectra of rhodamine-6G (R6G). We studied the physicochemical characterization of AgNPs, evaluated them as an antifungal agent against Candida albicans, Candida kruzei, Candida glabrata and Candida guilliermondii, and estimated their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values. Lastly, this study evaluated the cytotoxicity of the AgNPs in murine L929 fibroblasts cells using an MTT assay.

RESULTS

The UV-Vis spectroscopy, SERS, SEM and XRD results confirmed the rapid formation of spheroidal 30-50 nm AgNPs. The MIC and MFC values indicated the antifungal potential of AgNPs against most of the fungi studied and high cell viability in murine L929 fibroblasts. In addition, this study demonstrated that C. ferrea seed extracts may be used for the green synthesis of AgNPs at room temperature for the treatment of candidiasis.

Antifungal Activity of Commercial Essential Oils and Biocides against Candida Albicans

Management of oral candidosis, most frequently caused by Candida albicans, is limited due to the relatively low number of antifungal drugs and the emergence of antifungal tolerance. In this study, the antifungal activity of a range of commercial essential oils, two terpenes, chlorhexidine and triclosan was evaluated against C. albicans in planktonic and biofilm form. In addition, cytotoxicity of the most promising compounds was assessed using murine fibroblasts and expressed as half maximal inhibitory concentrations (IC50). Antifungal activity was determined using a broth microdilution assay. The minimum inhibitory concentration (MIC) was established against planktonic cells cultured in a range of concentrations of the test agents. The minimal biofilm eradication concentration (MBEC) was determined by measuring re-growth of cells after pre-formed biofilm was treated for 24 h with the test agents. All tested commercial essential oils demonstrated anticandidal activity (MICs from 0.06% (v/v) to 0.4% (v/v)) against planktonic cultures, with a noticeable increase in resistance exhibited by biofilms (MBECs > 1.5% (v/v)). The IC50s of the commercial essential oils were lower than the MICs, while a one hour application of chlorhexidine was not cytotoxic at concentrations lower than the MIC. In conclusion, the tested commercial essential oils exhibit potential as therapeutic agents against C. albicans, although host cell cytotoxicity is a consideration when developing these new treatments.

High Antifungal Activity against Candida Species of Monometallic and Bimetallic Nanoparticles Synthesized in Nanoreactors

Among all novel challenges nowadays worldwide, infectious disease is probably one of the most important. It is well-known that common treatments used include high doses of antibiotics, which are very invasive therapies for patients. These treatments are more intensive when the infection is related to multidrug resistant microorganisms. In this sense, in this work we report the use of reverse micelles to form less than 5 nm gold, silver, and gold-silver nanoparticles (NPs) with biological activity against five opportunistic Candida strains responsible of several diseases in human beings. As a result, we evaluate the interface properties and droplet-droplet interactions of micelles founding high fluidity in the polar head of the surfactant, necessary to form a flexible interaction channel in the "dimmer" micelle-micelle. In this condition, we form monodispersed, highly reactive NPs with sizes less than 5 nm with high antifungal activity against C. parapsilosis, C. Krusei, C. glabrata, C. guillermondii, and C. albicans, with minimum inhibitory concentrations (MIC₅₀) less than 0.7 ppm in all cases, the lowest reported to the best of our knowledge. These are very promising results to develop alternative therapies to treat fungal diseases in humans, animals, and plants, or to coat conventional surfaces in surgery rooms.

Future therapies targeted towards eliminating Candida biofilms and associated infections

INTRODUCTION

Candida species are common human commensals and cause either superficial or invasive opportunistic infections. The biofilm form of candida as opposed to its suspended, planktonic form, is predominantly associated with these infections. Alternative or adjunctive therapies are urgently needed to manage Candida infections as the currently available short arsenal of antifungal drugs has been compromised due to their systemic toxicity, cross-reactivity with other drugs, and above all, by the emergence of drug-resistant Candida species due to irrational drug use. Areas covered: Combination anti-Candida therapies, antifungal lock therapy, denture cleansers, and mouth rinses have all been proposed as alternatives for disrupting candidal biofilms on different substrates. Other suggested approaches for the management of candidiasis include the use of natural compounds, such as probiotics, plants extracts and oils, antifungal quorum sensing molecules, anti-Candida antibodies and vaccines, cytokine therapy, transfer of primed immune cells, photodynamic therapy, and nanoparticles. Expert commentary: The sparsity of currently available antifungals and the plethora of proposed anti-candidal therapies is a distinct indication of the urgent necessity to develop efficacious therapies for candidal infections. Alternative drug delivery approaches, such as probiotics, reviewed here is likely to be a reality in clinical settings in the not too distant future.

Current applications of nanoparticles in infectious diseases

For decades infections have been treated easily with drugs. However, in the 21st century, they may become lethal again owing to the development of antimicrobial resistance. Pathogens can become resistant by means of different mechanisms, such as increasing the time they spend in the intracellular environment, where drugs are unable to reach therapeutic levels. Moreover, drugs are also subject to certain problems that decrease their efficacy. This requires the use of high doses, and frequent administrations must be implemented, causing adverse side effects or toxicity. The use of nanoparticle systems can help to overcome such problems and increase drug efficacy. Accordingly, there is considerable current interest in their use as antimicrobial agents against different pathogens like bacteria, virus, fungi or parasites, multidrug-resistant strains and biofilms; as targeting vectors towards specific tissues; as vaccines and as theranostic systems. This review begins with an overview of the different types and characteristics of nanoparticles used to deliver drugs to the target, followed by a review of current research and clinical trials addressing the use of nanoparticles within the field of infectious diseases.

In vitro antifungal activity of silver nanoparticles against fluconazole-resistant Candida species

Nowadays, current advances in nanotechnology constitute a promising alternative in the development of new antimicrobial agents. Silver nanoparticles (AgNPs) are some very interesting products currently provided by available nanotechnology for control of microbial infection. In the present study, AgNPs were synthesized by eco-friendly method, using cysteine as a reducing agent. Also, antifungal activity against Candida species with resistance to fluconazole was evaluated through determination of Minimum Inhibitory Concentration (MIC50) according to protocol M27-A3 of Clinical and Laboratory Standards Institute (CLSI) and Minimum Fungicide Concentration (MFC). This study was carried out with strains Candida krusei and Candida glabrata. As a result, the formation of spherical nanoparticles was obtained with mean sizes of 19 nm and positive surface charge. Values of MIC50 were 0.1 µg ml(-1) AgNPs for the studied species, and MFC were 0.25 and 0.5 µg ml(-1) for C. glabrata and C. krusei, respectively. The AgNPs synthesized showed cytotoxic effect in 50% of Murine Fibroblast Cells (CC50) at a mean concentrations of 10 µg ml(-1) (100 times higher than MIC50). Consequently, AgNPs could be considered as an alternative potential in the development of new antifungal agents with minimum cytotoxicity in fibroblasts and lethal action on Candida species with resistance to conventional antifungal compounds.

Propolis: A Complex Natural Product with a Plethora of Biological Activities That Can Be Explored for Drug Development

The health industry has always used natural products as a rich, promising, and alternative source of drugs that are used in the health system. Propolis, a natural resinous product known for centuries, is a complex product obtained by honey bees from substances collected from parts of different plants, buds, and exudates in different geographic areas. Propolis has been attracting scientific attention since it has many biological and pharmacological properties, which are related to its chemical composition. Several in vitro and in vivo studies have been performed to characterize and understand the diverse bioactivities of propolis and its isolated compounds, as well as to evaluate and validate its potential. Yet, there is a lack of information concerning clinical effectiveness. The goal of this review is to discuss the potential of propolis for the development of new drugs by presenting published data concerning the chemical composition and the biological properties of this natural compound from different geographic origins.