Thymus vulgaris essential oil and thymol inhibit biofilms and interact synergistically with antifungal drugs against drug resistant strains of Candida albicans and Candida tropicalis

Mangiferin potentiates the activity of antifungal agents against fluconazole-resistant Candida spp

Aim: To evaluate the antifungal activity of mangiferin against Candida spp. resistant to fluconazole.Materials & methods: The antifungal activity of mangiferin was assessed using broth microdilution and its interaction with azoles and amphotericin B was evaluated by checkerboard. The activity of mangiferin against Candida spp. biofilms was assessed using the MTT colorimetric assay and its possible mechanism of action was evaluated using flow cytometry.Results: Mangiferin showed activity against Candida albicans, Candida tropicalis and Candida parapsilosis resistant to fluconazole and showed synergism with azoles and amphotericin B. Mangiferin increased the activity of antifungals against Candida biofilms and caused depolarization of the mitochondrial membrane and externalization of phosphatidylserine, suggesting apoptosis.Conclusion: mangiferin combined with antifungals has potential against Candida spp.

Determination of in vitro synergy and antibiofilm activities of antimicrobials and essential oil components

Using existing adrentimicrobials with essential oil components to prevent antimicrobial resistance is an alternative strategy. This study aimed to evaluate the resistance status, synergistic combinations, and in vitro biofilm formation activities of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), Stenotrophomonas maltophilia and Candida albicans against antimicrobial agents and cinnamaldehyde, carvacrol, eugenol, limonene and eucalyptol. Antimicrobial activities were evaluated by microdilution, cytotoxicity by XTT, synergy by checkerboard and time-kill, and biofilm inhibition by microplate methods. Cinnamaldehyde and carvacrol showed strong antimicrobial activity. Synergistic effects were observed when using all essential oils with antimicrobials. Only two C. albicans isolates showed antagonism with cinnamaldehyde and fluconazole. The constituents showed cytotoxic effects in the L929 cell line (except limonene). A time-kill analysis revealed a bacteriostatic effect on S. maltophilia and MRSA isolates and a fungicidal effect on C. albicans isolates. These results are important for further research to improve antimicrobial efficacy or to develop new agents.

Evaluation of antifungal spectrum of Cupferron against Candida albicans

Candida albicans is an opportunistic yeast accounting for about 50-90 % of all cases of candidiasis in humans, ranging from superficial to systemic potentially life-threatening infections. The presence of several virulence factors, including biofilm, hyphal transition, and proteolytic enzymes production, worsens the fungal infections burden on healthcare system resources. Hence, developing new bioactive compounds with antifungal activity is a pressing urgence for the scientific community. In this perspective, we evaluated the anti-Candida potential of the N-Nitroso-N-phenylhydroxylamine ammonium salt (cupferron) against standard and clinical C. albicans strains. Firstly, the in vitro cytotoxicity of cupferron was checked in the range 400-12.5 μg/mL against human microglial cells (HMC-3). Secondly, its antifungal spectrum was explored via disk diffusion test, broth-microdilution method, and time-killing curve analysis, validating the obtained results through scanning electron microscopy (SEM) observations. Additionally, we evaluated the cupferron impact on the main virulence determinants of Candida albicans. At non-toxic concentrations (100-12.5 μg/mL), the compound exerted interesting anti-Candida activity, registering a minimum inhibitory concentration (MIC) between 50 and 100 μg/mL against the tested strains, with a fungistatic effect until 100 μg/mL. Furthermore, cupferron was able to counteract fungal virulence at MIC and sub-MIC values (50-12.5 μg/mL). These findings may propose cupferron as a new potential antifungal option for the treatment of Candida albicans infections.

Phytochemical Analysis and Antioxidant and Antifungal Activities of Powders, Methanol Extracts, and Essential Oils from Rosmarinus officinalis L. and Thymus ciliatus Desf. Benth

Chemical residues in food pose health risks such as cancer and liver issues. This has driven the search for safer natural alternatives to synthetic fungicides and preservatives. The aim of this study was to characterize the chemical composition of the essential oils (EO), determine the polyphenolic contents, and evaluate the in vitro antioxidant and antifungal activities of methanol extracts (ME), essential oils (EO), and powders from Rosmarinus officinalis L. (rosemary) and Thymus ciliatus (Desf) Benth. (thyme) from the M'sila region, Algeria. The chemical composition of the EOs was determined by GC-MS. R. officinalis EO was composed of 31 components, mainly camphor (41.22%), camphene (18.14%), and α-pinene (17.49%); T. ciliatus EO was composed of 58 components, mainly, in percentage, α-pinene (22.18), myrcene (13.13), β-pinene (7.73), β-caryophyllene (10.21), and germacrene D (9.90). The total phenols and flavonoids were determined spectrophotometrically, and the rosemary ME was found to possess the highest polyphenolic content (127.1 ± 2.40 µg GAE/mg), while the thyme ME had the highest flavonoid content (48.01 ± 0.99 µg QE/mg). The antioxidant activity was assessed using three methods: rosemary ME was the most potent, followed by DPPH (IC50 = 13.43 ± 0.14 µg/mL), β-carotene/linoleic acid (IC50 = 39.01 ± 2.16 μg/mL), and reducing power (EC50 = 15.03 ± 1.43 µg/mL). Antifungal activity was assessed for 32 pathogenic and foodborne fungi. Four methods were applied to the solid medium. Incorporating the powdered plant into the culture medium (at 10%) reduced the fungal growth to greater than 50% in 21.88% and 6.25% of all fungal isolates, for R. officinalis and T. ciliatus, respectively. The ME, applied by the well diffusion method (0.1 g/mL), was less effective. Different concentrations of EO were tested. Incorporating the EO into the culture medium (1500 μL/L) inhibited 50% of the molds to levels of 50 and 75% for R. officinalis and T. ciliatus, respectively, with the complete inhibition of four fungi. Fumigated EO (15 μL) inhibited 65% of the molds to levels of 65 and 81.25% for R. officinalis and T. ciliatus, respectively, with the complete inhibition of five fungi. There was little to no sporulation in conjunction with the inhibition. Our results revealed some of the potential of the studied plants to fight foodborne molds and presented their promising characteristics as a source of alternatives to chemical pesticides and synthetic preservatives. Further studies are needed to find adequate application techniques in the food safety area.

Biofilm inhibition of denture cleaning tablets and carvacrol on denture bases produced with different techniques

OBJECTIVES

This study compares the biofilm inhibition effects of denture cleaning tablets, carvacrol, and their combined use against Candida albicans on denture bases produced with different techniques. Additionally, the surface roughness and contact angles of these denture bases were evaluated.

MATERIALS AND METHODS

Test samples were prepared from four different denture base materials (cold-polymerized, heat-polymerized, CAD/CAM milling, and 3D-printed). The surface roughness and contact angles of the test samples were measured using a profilometer and goniometer, respectively. For the evaluation of biofilm inhibition, samples were divided into 5 subgroups: Corega and carvacrol, separately and combined treatments, positive (inoculated with C. albicans) and negative control (non-inoculated with C. albicans, only medium). Biofilm mass was determined using the crystal violet method. An additional prepared test sample for each subgroup was examined under scanning electron microscopy (SEM).

RESULTS

The surface roughness values of the 3D-printed test samples were found to be statistically higher than the other groups (P < .001). The water contact angle of all test materials was not statistically different from each other (P > .001). Corega and carvacrol, separately and combined, significantly decreased the amount of biofilm on all surfaces (P < .0001). Treatment of corega alone and in combination with carvacrol to the 3D-printed material caused less C. albicans inhibition than the other groups (P < .001; P < .05).

CONCLUSIONS

The surface roughness values of all test groups were within the clinically acceptable threshold. Although Corega and carvacrol inhibited C. albicans biofilms, their combined use did not show a synergistic effect.

CLINICAL RELEVANCE

Carvacrol may be used as one of the disinfectant agents for denture cleaning due to its biofilm inhibition property.

New thymol-derived triazole exhibits promising activity against Trichophyton rubrum

Fungal infections have emerged worldwide, and azole antifungals are widely used to control these infections. However, the emergence of antifungal resistance has been compromising the effectiveness of these drugs. Therefore, the objective of this study was to evaluate the antifungal and cytotoxic activities of the nine new 1,2,3 triazole compounds derived from thymol that were synthesized through Click chemistry. The binding mode prediction was carried out by docking studies using the crystallographic structure of Lanosterol 14α-demethylase G73E mutant from Saccharomyces cerevisiae. The new compounds showed potent antifungal activity against Trichophyton rubrum but did not show relevant action against Aspergillus fumigatus and Candida albicans. For T. rubrum, molecules nº 5 and 8 showed promising results, emphasizing nº 8, whose fungicidal and fungistatic effects were similar to fluconazole. In addition, molecule nº 8 showed low toxicity for keratinocytes and fibroblasts, concluding that this compound demonstrates promising characteristics for developing a new drug for dermatophytosis caused by T. rubrum, or serves as a structural basis for further research.

Impact of Cuminaldehyde and Indomethacin Co-Administration on Inflammatory Responses in MIA-Induced Osteoarthritis in Rats

Osteoarthritis (OA) remains a chronic incurable condition, presenting substantial challenges in treatment. This study explores a novel strategy by investigating the concurrent use of cuminaldehyde, a natural compound, with indomethacin in animal models of MIA-induced OA. Our results demonstrate that the co-administration of cuminaldehyde and indomethacin does indeed produce a superior effect when compared to these compounds individually, significantly enhancing therapeutic outcomes. This effect is evidenced by a marked reduction in pro-inflammatory cytokines IL-6 and IFN-γ, alongside a significant increase in the anti-inflammatory cytokine IL-10, compared to treatments with each compound alone. Radiographic analyses further confirm the preservation of joint integrity and a reduction in osteoarthritic damage, highlighting the association's efficacy in cartilage-reducing damage. These findings suggests that the association of cuminaldehyde and indomethacin not only slows OA progression but also offers enhanced cartilage-reducing damage and fosters the production of protective cytokines. This study underscores the potential benefits of integrating natural products with pharmaceuticals in OA management and stresses the importance of further research to fully understand the mechanisms underlying the observed potentiated effects.

Insights into the anti-Candida albicans properties of natural phytochemicals: An in vitro and in vivo investigation

Invasive candidiasis, attributed to Candida albicans, has long been a formidable threat to human health. Despite the advent of effective therapeutics in recent decades, the mortality rate in affected patient populations remains discouraging. This is exacerbated by the emergence of multidrug resistance, significantly limiting the utility of conventional antifungals. Consequently, researchers are compelled to continuously explore novel solutions. Natural phytochemicals present a potential adjunct to the existing arsenal of agents. Previous studies have substantiated the efficacy of phytochemicals against C. albicans. Emerging evidence also underscores the promising application of phytochemicals in the realm of antifungal treatment. This review systematically delineates the inhibitory activity of phytochemicals, both in monotherapy and combination therapy, against C. albicans in both in vivo and in vitro settings. Moreover, it elucidates the mechanisms underpinning the antifungal properties, encompassing (i) cell wall and plasma membrane damage, (ii) inhibition of efflux pumps, (iii) induction of mitochondrial dysfunction, and (iv) inhibition of virulence factors. Subsequently, the review introduces the substantial potential of nanotechnology and photodynamic technology in enhancing the bioavailability of phytochemicals. Lastly, it discusses current limitations and outlines future research priorities, emphasizing the need for high-quality research to comprehensively establish the clinical efficacy and safety of phytochemicals in treating fungal infections. This review aims to inspire further contemplation and recommendations for the effective integration of natural phytochemicals in the development of new medicines for patients afflicted with C. albicans.

In vitro evaluation of the antimicrobial properties of terpinen-4-ol on apical periodontitis-associated bacteria

Manuka oil and tea tree oil are essential oils with known antibacterial properties that are believed to be caused by one main component: terpinen-4-ol. Terpinen-4-ol has potent antibacterial activity against caries-related microorganisms. However, few studies have investigated the antimicrobial effects of terpinen-4-ol on bacteria in apical periodontitis. Thus, the objective of the present study was to evaluate the antibacterial and antibiofilm potential of terpinen-4-ol against Enterococcus faecalis, Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum, which have all been detected in apical periodontitis. The minimum inhibitory and minimum bactericidal concentrations of terpinen-4-ol were determined to assess its activity against biofilms. The minimum inhibitory concentration of terpinen-4-ol was 0.25% against E. faecalis and F. nucleatum, 0.05% against P. gingivalis, and 0.1% against P. intermedia. The minimum bactericidal concentration of terpinen-4-ol was 1.0% against E. faecalis, 0.2% against P. gingivalis and P. intermedia, and 0.5% against F. nucleatum. In the biofilm evaluations, all terpinen-4-ol-treated bacteria had significant reductions in biofilm viability compared with controls in experiments assessing attachment inhibitory activity. Furthermore, structural alterations and decreased bacterial cell clumping were observed under scanning electron microscopy, and significantly decreased cell survival was noted using fluorescence microscopy. Together, these results suggest that terpinen-4-ol is a potential antibacterial agent with bactericidal properties, and can also act on established biofilms.

Antibiofilm Activity of Curcumin and Piperine and Their Synergistic Effects with Antifungals against Candida albicans Clinical Isolates

Background

Candidiasis is the common name for diseases caused by yeast of the genus Candida. Candida albicans is one of the most implicated species in superficial and invasive candidiasis. Antifungals, polyenes, and azoles have been used to treat candidiasis. However, due to the development of antifungal resistance, research of natural substances with potential antifungal effects at low concentrations or combined is also a possibility.

Methods

The broth microdilution method was used to evaluate the antifungal activity. The biofilm formation was assessed using the microtiter plate method. The antibiofilm activities were assessed using micro plaque tetrazolium salt assay (MTT). The combination effect of antifungal with natural substances was made using the checkerboard method.

Results

Among our isolates, clotrimazole was the most resistant, but amphotericin B was the most effective antifungal. The biofilm was formed by all isolates of C. albicans. Curcumin and piperine displayed antibiofilm activity with minimum biofilm inhibitory concentration (MBIC) and minimum eradicating concentration (MBEC) ranging from 64 to 1024 μg/mL and 256 to 2048 μg/mL. In combination, piperine presented double synergistic effects compared to curcumin with all antifungals tested. Curcumin shows more synergistic effect when combined with polyenes than with azoles. However, piperine shows a more synergistic effect when combined with azoles compared to polyenes.

Conclusion

C. albicans was susceptible to curcumin and piperine both on planktonic cells and biofilm. The combination of curcumin and piperine with antifungals has shown synergistic effects against multiresistant clinical isolates of Candida albicans representing an alternative drug research for the treatment of clinical candidiasis.

RNA-Seq-Based Transcriptomics and GC-MS Quantitative Analysis Reveal Antifungal Mechanisms of Essential Oil of Clausena lansium (Lour.) Skeels Seeds against Candida albicans

Infections caused by Candida albicans (C. albicans) and increasing resistance to commonly used drugs lead to a variety of mucosal diseases and systemic infectious diseases. We previously confirmed that the essential oil of Clausena lansium (Lour.) Skeels seeds (CSEO) had antifungal activity against C. albicans, but the detailed mechanism between the chemical components and antifungal activity is unclear. In this study, a quantitative analysis of five volatile components of CSEO, including sabinene, α-phellandrene, β-phellandrene, 4-terpineol, and β-caryophyllene, was carried out using the gas chromatography-mass spectrometry (GC-MS) method. Both the broth dilution and kinetic growth methods proved that the antifungal activity of CSEO against fluconazole-resistant C. albicans was better than that of its main components (sabinene and 4-terpineol). To further investigate the inhibitory mechanism, the transcriptional responses of C. albicans to CSEO, sabinene, and 4-terpineol treatment were determined based on RNA-seq. The Venn diagram and clustering analysis pattern of differential expression genes showed the mechanism of CSEO and 4-terpineol's anti-C. albicans activity might be similar from the perspective of the genes. Functional enrichment analysis suggested that CSEO regulated adherence-, hyphae-, and biofilm-formation-related genes, which may be CSEO's active mechanism of inhibiting the growth of fluconazole-resistant C. albicans. Overall, we preliminarily revealed the molecular mechanism between the chemical components and the antifungal activity of CSEO against C. albicans. This study provides new insights to overcome the azole resistance of C. albicans and promote the development and application of C. lansium (Lour.) Skeels seeds.

A comparative study on DNA and protein binding properties of thymol and thymoquinone

Two phytochemicals, thymol and thymoquinone obtained from thymes (Thymus vulgaris L., Lamiaceae etc.) and Nagila Sativa seed, respectively. Both the phytochemicals show several biochemical activities like anticancer, antimicrobial etc. In this paper, we studied the affinities of thymol and thymoquinone towards calf thymus DNA (CT-DNA) and protein (bovine serum albumin). Spectroscopic and molecular modelling studies revealed that both compounds have a high affinity toward both the receptors; DNA and protein. Both phytochemicals binds to the minor grooves of DNA and suitable pockets of protein. Several free energy function and hydrogen bonding play significant role during the binding phenomenon.Communicated by Ramaswamy H. Sarma.

An In Vitro Comparative Evaluation of Conventional and Novel Thymus vulgaris Derived Herbal Disinfectant Solutions against Pathogenic Biofilm on Maxillofacial Silicones and Its Impact on Color Stability

AIM

This study aims to assess the antimicrobial efficacy and impact on color stability of Thymus (T.) vulgaris solution compared to conventional disinfectants on maxillofacial silicones.

MATERIALS AND METHODS

Various solutions were evaluated, including T. vulgaris solutions at 5 and 10%, saline (control), chlorhexidine (4%), and soap water. The substrates were MDX4-4210 silicone elastomers, and the microorganisms tested were Candida (C.) albicans and Staphylococcus (S.) aureus. The viability of microorganisms was determined through an 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) reduction assay, and color stability was measured using a spectrophotometer with X-Rite Europe software. Statistical analysis was performed using the Kruskal-Wallis test, Mann-Whitney U post hoc test, and Wilcoxon Signed Rank test.

RESULTS

Soap water demonstrated superior disinfectant action against both microorganisms, while T. vulgaris solutions at 5 and 10% exhibited comparable antimicrobial efficacy. Chlorhexidine and 10% T. vulgaris solution showed minimal color changes in the silicone material. In contrast, soap water and the 5% T. vulgaris solution resulted in clinically unacceptable color alterations.

CONCLUSION

This study underscores the potential of T. vulgaris as an herbal disinfectant for combating microbial biofilms on maxillofacial silicones, particularly at concentrations of 5 and 10%. The importance of maintaining color stability is emphasized, with Chlorhexidine and the 10% T. vulgaris solution demonstrating effective preservation of esthetics. These findings suggest the viability of considering T. vulgaris as an alternative disinfectant in clinical settings for maxillofacial silicone prostheses.

CLINICAL SIGNIFICANCE

Maxillofacial silicones are vital in restoring aesthetic features for individuals with facial trauma, congenital deformities, or post-surgical interventions. Yet, biofilm-related infections jeopardize their durability and visual integrity. Clinically, T. vulgaris signifies a potential advance in prosthodontic care, offering valuable insights for improving antimicrobial performance and aesthetic durability in maxillofacial prostheses. How to cite this article: Peter M, Kanathila H, Bembalagi M, et al. An In Vitro Comparative Evaluation of Conventional and Novel Thymus vulgaris Derived Herbal Disinfectant Solutions against Pathogenic Biofilm on Maxillofacial Silicones and Its Impact on Color Stability. J Contemp Dent Pract 2023;24(12):967-973.

Natural Compounds with Antifungal Properties against Candida albicans and Identification of Hinokitiol as a Promising Antifungal Drug

Candida albicans is an opportunistic yeast that causes most fungal infections. C. albicans has become increasingly resistant to antifungal drugs over the past decade. Our study focused on the identification of pure natural compounds for the development of antifungal medicines. A total of 15 natural compounds from different chemical families (cinnamic derivatives, aromatic phenols, mono- and sesquiterpenols, and unclassified compounds) were screened in this study. Among these groups, hinokitiol (Hi), a natural monoterpenoid extracted from the wood of the cypress family, showed excellent anti-C. albicans activity, with a MIC value of 8.21 µg/mL. Hi was selected from this panel for further investigation to assess its antifungal and anti-inflammatory properties. Hi exhibited significant antifungal activity against clinically isolated fluconazole- or caspofungin-resistant C. albicans strains. It also reduced biofilm formation and hyphal growth. Treatment with Hi protected Caenorhabditis elegans against infection with C. albicans and enhanced the expression of antimicrobial genes in worms infected with C. albicans. Aside from its antifungal activities against C. albicans, Hi challenge attenuated the LPS-induced expression of pro-inflammatory cytokines (IL-6, IL-1β, and CCL-2) in macrophages. Overall, Hi is a natural compound with antifungal and anti-inflammatory properties, making Hi a promising platform with which to fight against fungal infections.

Antifungal Activity and Type of Interaction of Melissa officinalis Essential Oil with Antimycotics against Biofilms of Multidrug-Resistant Candida Isolates from Vulvovaginal Mucosa

(1) Background: Vulvovaginal candidosis (VVC) is a major therapy issue due to its high resistance rate and virulence factors such as the ability to form biofilms. The possibility of combining commonly used antifungals with natural products might greatly improve therapeutic success. (2) Methods: A total of 49 vulvovaginal isolates, causative agents of recurrent VVC, were tested for their susceptibility to fluconazole, nystatin, and Melissa officinalis essential oil (MOEO). This examination included testing the antibiofilm potential of antifungals and MOEO and the determination of their types of interaction with mature biofilms. (3) Results: Antimicrobial testing showed that 94.4% of the Candida albicans isolates and all the Candida krusei isolates were resistant to fluconazole, while all strains showed resistance to nystatin. The same strains were susceptible to MOEO in 0.156-2.5 mg/mL concentrations. Additionally, the results revealed very limited action of fluconazole, while nystatin and MOEO reduced the amount of biofilm formed by as much as 17.7% and 4.6%, respectively. Testing of the combined effect showed strain-specific synergistic action. Furthermore, the lower concentrations exhibited antagonistic effects even in cases where synergism was detected. (4) Conclusions: This study showed that MOEO had a very good antibiofilm effect. However, combining MOEO with antimycotics demonstrated that the type of action depended on the choice of antifungal drugs as well as the applied concentration.

Synergistic Effect of Plant Compounds in Combination with Conventional Antimicrobials against Biofilm of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida spp

Bacterial and fungal biofilm has increased antibiotic resistance and plays an essential role in many persistent diseases. Biofilm-associated chronic infections are difficult to treat and reduce the efficacy of medical devices. This global problem has prompted extensive research to find alternative strategies to fight microbial chronic infections. Plant bioactive metabolites with antibiofilm activity are known to be potential resources to alleviate this problem. The phytochemical screening of some medicinal plants showed different active groups, such as stilbenes, tannins, alkaloids, terpenes, polyphenolics, flavonoids, lignans, quinones, and coumarins. Synergistic effects can be observed in the interaction between plant compounds and conventional drugs. This review analyses and summarises the current knowledge on the synergistic effects of plant metabolites in combination with conventional antimicrobials against biofilms of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. The synergism of conventional antimicrobials with plant compounds can modify and inhibit the mechanisms of acquired resistance, reduce undesirable effects, and obtain an appropriate therapeutic effect at lower doses. A deeper knowledge of these combinations and of their possible antibiofilm targets is needed to develop next-generation novel antimicrobials and/or improve current antimicrobials to fight drug-resistant infections attributed to biofilm.

Current and Potential Applications of Monoterpenes and Their Derivatives in Oral Health Care

Plant products have been employed in medicine for centuries. As the world becomes more health-conscious, there is a growing interest in natural and minimally processed products for oral health care. This has led to an increase in research into the bioactive compounds found in plant products, particularly monoterpenes. Monoterpenes are known to have beneficial biological properties, but the specific mechanisms by which they exert their effects are not yet fully understood. Despite this, some monoterpenes are already being used in oral health care. For example, thymol, which has antibacterial properties, is an ingredient in varnish used for caries prevention. In addition to this, monoterpenes have also demonstrated antifungal, antiviral, and anti-inflammatory properties, making them versatile for various applications. As research continues, there is potential for even more discoveries regarding the benefits of monoterpenes in oral health care. This narrative literature review gives an overview of the biological properties and current and potential applications of selected monoterpenes and their derivatives in oral health care. These compounds demonstrate promising potential for future medical development, and their applications in future research are expected to expand.

Biofilm Formation in Medically Important Candida Species

Worldwide, the number of infections caused by biofilm-forming fungal pathogens is very high. In human medicine, there is an increasing proportion of immunocompromised patients with prolonged hospitalization, and patients with long-term inserted drains, cannulas, catheters, tubes, or other artificial devices, that exhibit a predisposition for colonization by biofilm-forming yeasts. A high percentage of mortality is due to candidemia caused by medically important Candida species. Species of major clinical significance include C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. krusei, and C. auris. The association of these pathogenic species in the biofilm structure is a serious therapeutic problem. Candida cells growing in the form of a biofilm are able to resist persistent therapy thanks to a combination of their protective mechanisms and their ability to disseminate to other parts of the body, thus representing a threat from the perspective of a permanent source of infection. The elucidation of the key mechanisms of biofilm formation is essential to progress in the understanding and treatment of invasive Candida infections.

Lippia origanoides Essential Oil or Thymol in Combination with Fluconazole Produces Damage to Cells and Reverses the Azole-Resistant Phenotype of a Candida tropicalis Strain

Candida tropicalis is one of the most pathogenic species within the genus. Increased antifungal resistance has been reported, which is in part due to the organism's ability to form biofilms. In natural products derived from plants, such as essential oils (EOs) or their major components, there is significant potential to develop new antifungals or to both enhance the efficacy and reduce the toxicity of conventional antifungals. This study aimed to evaluate the effect of combining an EO of Lippia origanoides or thymol with fluconazole on an azole-resistant C. tropicalis strain. Synergism was observed in the combination of fluconazole with the EO and with thymol, and minimal inhibitory concentrations for fluconazole decreased at least 32-fold. As a consequence of the synergistic interactions, mitochondrial membrane potential was reduced, and mitochondrial superoxide production increased. Alteration in nuclear morphology, cell surface, and ultrastructure was also observed. In conclusion, the synergistic interaction between L. origanoides EO or thymol with fluconazole reverted the azole-resistant C. tropicalis phenotype. These findings suggest that L. origanoides EO or thymol alone, or in combination with fluconazole, have the potential for development as antifungal therapies for this yeast, including resistant strains.

Reviving the interest in the versatile drug nystatin: A multitude of strategies to increase its potential as an effective and safe antifungal agent

Nystatin is an antifungal molecule with a remarkable yet squandered versatility. In this review, its mechanism of action is explored, along with its extensive action spectrum and toxicity. A multitude of methodologies to tackle the drug's physical and chemical hurdles are outlined along with some proven-effective strategies to increase its activity and/or decrease its toxicity. A separate detailed section focused on micro and nanotechnology solutions addresses new drug delivery systems made of polymeric, metallic or lipid materials. Although the topical route depicts greater representativeness amongst these formulations, the intravenous, dental, oral, vaginal and inhalation routes are also mentioned. The unsuccessful previous attempts at developing parenteral formulations of nystatin or even the withdrawal of a nystatin-loaded multilamellar liposome should not divert research away from this drug. In fact, the interest in nystatin ought to be reawakened with the ongoing clinical trials on the promising nystatin-like genetically engineered derivate BSG005.

Healthy Diet and Lifestyle Improve the Gut Microbiota and Help Combat Fungal Infection

Western diets are rapidly spreading due to globalization, causing an increase in obesity and diseases of civilization. These Western diets are associated with changes in the gut microbiota related to intestinal inflammation. This review discusses the adverse effects of Western diets, which are high in fat and sugar and low in vegetable fiber, on the gut microbiota. This leads to gut dysbiosis and overgrowth of Candida albicans, which is a major cause of fungal infection worldwide. In addition to an unhealthy Western diet, other factors related to disease development and gut dysbiosis include smoking, excessive alcohol consumption, lack of physical activity, prolonged use of antibiotics, and chronic psychological stress. This review suggests that a diversified diet containing vegetable fiber, omega-3 polyunsaturated fatty acids, vitamins D and E, as well as micronutrients associated with probiotic or prebiotic supplements can improve the biodiversity of the microbiota, lead to short-chain fatty acid production, and reduce the abundance of fungal species in the gut. The review also discusses a variety of foods and plants that are effective against fungal overgrowth and gut dysbiosis in traditional medicine. Overall, healthy diets and lifestyle factors contribute to human well-being and increase the biodiversity of the gut microbiota, which positively modulates the brain and central nervous system.

The potential role of plant secondary metabolites on antifungal and immunomodulatory effect

With the widespread use of antibiotic drugs worldwide and the global increase in the number of immunodeficient patients, fungal infections have become a serious threat to global public health security. Moreover, the evolution of fungal resistance to existing antifungal drugs is on the rise. To address these issues, the development of new antifungal drugs or fungal inhibitors needs to be targeted urgently. Plant secondary metabolites are characterized by a wide variety of chemical structures, low price, high availability, high antimicrobial activity, and few side effects. Therefore, plant secondary metabolites may be important resources for the identification and development of novel antifungal drugs. However, there are few studies to summarize those contents. In this review, the antifungal modes of action of plant secondary metabolites toward different types of fungi and fungal infections are covered, as well as highlighting immunomodulatory effects on the human body. This review of the literature should lay the foundation for research into new antifungal drugs and the discovery of new targets. KEY POINTS: • Immunocompromised patients who are infected the drug-resistant fungi are increasing. • Plant secondary metabolites toward various fungal targets are covered. • Plant secondary metabolites with immunomodulatory effect are verified in vivo.

Genotoxic Potential of Thymol on Honey Bee DNA in the Comet Assay

Thymol is a natural essential oil derived from the plant Thymus vulgaris L. It is known to be beneficial for human and animal health and has been used in beekeeping practice against Varroa mite for years. In this study, the genotoxic and antigenotoxic potential of thymol were evaluated on the honey bee (Apis mellifera L.) continuous cell line AmE-711 for the first time. Using the Comet assay, three increasing concentrations (10, 100, and 1000 µg/mL) of thymol were tested. Negative control (non-treated cells) and positive control (cells treated with 100 µM H₂O₂) were also included. The absence of thymol cytotoxicity was confirmed with the Trypan blue exclusion test. Thymol in the concentration of 10 µg/mL did not increase DNA damage in AmE-711 honey bee cells, while 100 and 1000 µg/mL concentrations showed genotoxic effects. For testing the antigenotoxic effect, all concentrations of thymol were mixed and incubated with H₂O₂. The antigenotoxic effect against was absent at all concentrations (10, 100, 1000 μg/mL) tested. Moreover, thymol enhanced the H₂O₂-induced DNA migration in the Comet assay. The obtained results indicate genotoxic effects of thymol on cultured honey bee cells suggesting its careful application in beekeeping practice to avoid possible negative effects on honey bees.

Carvacrol-A Natural Phenolic Compound with Antimicrobial Properties

The main purpose of this article is to present the latest research related to selected biological properties of carvacrol, such as antimicrobial, anti-inflammatory, and antioxidant activity. As a monoterpenoid phenol, carvacrol is a component of many essential oils and is usually found in plants together with its isomer, thymol. Carvacrol, either alone or in combination with other compounds, has a strong antimicrobial effect on many different strains of bacteria and fungi that are dangerous to humans or can cause significant losses in the economy. Carvacrol also exerts strong anti-inflammatory properties by preventing the peroxidation of polyunsaturated fatty acids by inducing SOD, GPx, GR, and CAT, as well as reducing the level of pro-inflammatory cytokines in the body. It also affects the body's immune response generated by LPS. Carvacrol is considered a safe compound despite the limited amount of data on its metabolism in humans. This review also discusses the biotransformations of carvacrol, because the knowledge of the possible degradation pathways of this compound may help to minimize the risk of environmental contamination with phenolic compounds.

On the Future Perspectives of Some Medicinal Plants within Lamiaceae Botanic Family Regarding Their Comprehensive Properties and Resistance against Biotic and Abiotic Stresses

Lamiaceae is one of the largest botanical families, encompassing over 6000 species that include a variety of aromatic and medicinal spices. The current study is focused on three plants within this botanical family: basil (Ocimum basilicum L.), thyme (Thymus vulgaris L.), and summer savory (Satureja hortensis L.). These three species contain primary and secondary metabolites such as phenolic and flavonoid compounds, fatty acids, antioxidants, and essential oils and have traditionally been used for flavoring, food preservation, and medicinal purposes. The goal of this study is to provide an overview of the nutraceutical, therapeutic, antioxidant, and antibacterial key features of these three aromatics to explore new breeding challenges and opportunities for varietal development. In this context, a literature search has been performed to describe the phytochemical profile of both primary and secondary metabolites and their pharmacological uses, as well as to further explore accession availability in the medicine industry and also to emphasize their bioactive roles in plant ecology and biotic and abiotic stress adaptability. The aim of this review is to explore future perspectives on the development of new, highly valuable basil, summer savory, and thyme cultivars. The findings of the current review emphasize the importance of identifying the key compounds and genes involved in stress resistance that can also provide valuable insights for further improvement of these important medicinal plants.

Antifungal and Antibiofilm Activity of Colombian Essential Oils against Different Candida Strains

Most Candida species are opportunistic pathogens with the ability to form biofilms, which increases their resistance to antifungal drug therapies and the host immune response. Essential oils (EOs) are an alternative for developing new antimicrobial drugs, due to their broad effect on cellular viability, cell communication, and metabolism. In this work, we evaluated the antifungal and antibiofilm potential of fifty EOs on C. albicans ATCC 10231, C. parapsilosis ATCC 22019, and Candida auris CDC B11903. The EOs’ antifungal activity was measured by means of a broth microdilution technique to determine the minimum inhibitory and fungicidal concentrations (MICs/MFCs) against the different Candida spp. strains. The effects on biofilm formation were determined by a crystal violet assay using 96-well round-bottom microplates incubated for 48 h at 35 °C. The EOs from Lippia alba (Verbenaceae family) carvone-limonene chemotype and L. origanoides exhibited the highest antifungal activity against C. auris. The L. origanoides EOs also presented antifungal and antibiofilm activity against all three Candida spp., thus representing a promising alternative for developing new antifungal products focused on yeast infections, especially those related to biofilm formation, virulence factors, and antimicrobial resistance.

Rational design, synthesis, antifungal evaluation and docking studies of antifungal peptide CGA-N12 analogues based on the target CtKRE9

Candida tropicalis is a major non-albicans species that causes invasive candidiasis. CGA-N12, an anti-Candida peptide found by our group, disrupted cell wall architecture by inhibiting the activity of the protein killer-resistant 9 (KRE9), a β-1,6-glucan synthase specific to Candida spp. and plants. Herein, a set of CGA-N12 analogues were rationally designed based on the interaction networks between CGA-N12 and C. tropicalis KRE9 (CtKRE9). Seven CGA-N12 analogues with significantly improved antifungal activity against C. tropicalis were screened by reducing the docking energy of CGA-N12 and CtKRE9 and increasing the number of positive charges on CGA-N12 based on a stable three-dimensional model of CtKRE9. CGA-N12 and its analogues exhibited antifungal activity against C. tropicalis and its persist cells; they also inhibited biofilm formation and eradicated preformed biofilms. Compared with fluconazole, they displayed higher activities against the growth of persister cells and more effective preformed biofilm eradication. Among them, CGA-N12-0801, CGA-N12-0902 and CGA-N12-1002 displayed much higher activity and anti-proteinase digestion stability than CGA-N12. Specifically, CGA-N12-0801 was the optimal analogue, with a minimum inhibitory concentration of 3.46 μg/mL and a therapeutic index of 158.07. The results of electronic microscopy observations and KRE9 activity inhibition assays showed that CGA-N12 and its analogues killed C. tropicalis by disrupting the architecture of the cell wall and the integrity of the cell membrane. In conclusion, for the first time, we provide a simple and reliable method for the rational design of antimicrobial peptides and ideal candidates for treating Candida infections that not effectively eliminated by azole drugs.

Revisiting the Therapeutic Effects of Essential Oils on the Oral Microbiome

The extensive use of antibiotics has resulted in the development of drug-resistant bacteria, leading to a decline in the efficacy of traditional antibiotic treatments. Essential oils (EOs) are phytopharmaceuticals, or plant-derived compounds, that possess beneficial properties such as anti-inflammatory, antibacterial, antimicrobial, antiviral, bacteriostatic, and bactericidal effects. In this review, we present scientific findings on the activity of EOs as an alternative therapy for common oral diseases. This narrative review provides a deeper understanding of the medicinal properties of EOs and their application in dentistry. It not only evaluates the effectiveness of these oils as antibacterial agents against common oral bacteria but also covers general information such as composition, methods of extraction, and potential toxicity. Further nonclinical and clinical studies must be conducted to determine their potential use and safety for treating oral diseases.

GC, GC/MS Analysis, and Biological Effects of Essential Oils from Thymus mastchina and Elettaria cardamomum

Spanish marjoram (Thymus mastichina) and cardamom (Elettaria cardamomum) are traditional aromatic plants with which several pharmacological properties have been associated. In this study, the volatile composition, antioxidative and antimigratory effects on human breast cancer (MDA-MB-468 cell line), antimicrobial activity, and antibiofilm effect were evaluated. Results obtained via treatment of human breast cancer cells generally indicated an inhibitory effect of both essential oils (EOs) on cell viability (after long-term treatment) and antioxidative potential, as well as the reduction of nitric oxide levels. Antimigratory effects were revealed, suggesting that these EOs could possess significant antimetastatic properties and stop tumor progression and growth. The antimicrobial activities of both EOs were determined using the disc diffusion method and minimal inhibition concentration, while antibiofilm activity was evaluated by means of mass spectrometry. The best antimicrobial effects of T. mastichina EO were found against the yeast Candida glabrata and the G⁺ bacterium Listeria monocytogenes using the disc diffusion and minimal inhibitory concentration methods. E. cardamomum EO was found to be most effective against Pseudomas fluorescens biofilm using both methods. Similarly, better effects of this oil were observed on G^- compared to G⁺ bacterial strains. Our study confirms that T. mastichina and E. cardamomum EOs act to change the protein structure of older P. fluorescens biofilms. The results underline the potential use of these EOs in manufactured products, such as foodstuffs, cosmetics, and pharmaceuticals.

In Vitro Activity of Essential Oils Distilled from Colombian Plants against Candidaauris and Other Candida Species with Different Antifungal Susceptibility Profiles

Multi-drug resistant species such as Candida auris are a global health threat. This scenario has highlighted the need to search for antifungal alternatives. Essential oils (EOs), or some of their major compounds, could be a source of new antifungal molecules. The aim of this study was to evaluate the in vitro activity of EOs and some terpenes against C. auris and other Candida spp. The eleven EOs evaluated were obtained by hydro-distillation from different Colombian plants and the terpenes were purchased. EO chemical compositions were obtained by gas chromatography/mass spectrometry (GC/MS). Antifungal activity was evaluated following the CLSI standard M27, 4th Edition. Cytotoxicity was tested on the HaCaT cell line and fungal growth kinetics were tested by time–kill assays. Candida spp. showed different susceptibility to antifungals and the activity of EOs and terpenes was strain-dependent. The Lippia origanoides (thymol + p-cymene) chemotype EO, thymol, carvacrol, and limonene were the most active, mainly against drug-resistant strains. The most active EOs and terpenes were also slightly cytotoxic on the HaCaT cells. The findings of this study suggest that some EOs and commercial terpenes can be a source for the development of new anti-Candida products and aid the identification of new antifungal targets or action mechanisms.

Hydrothermal assisted biogenic synthesis of silver nanoparticles: A potential study on virulent candida isolates from COVID-19 patients

Till now the exact mechanism and effect of biogenic silver nanoparticles on fungus is an indefinable question. To focus on this issue, the first time we prepared hydrothermal assisted thyme coated silver nanoparticles (T/AgNPs) and their toxic effect on Candida isolates were determined. The role of thyme (Thymus Vulgaris) in the reduction of silver ions and stabilization of T/AgNPs was estimated by Fourier transforms infrared spectroscopy, structure and size of present silver nanoparticles were detected via atomic force microscopy as well as high-resolution transmission electron microscopy. The biological activity of T/AgNPs was observed against Candida isolates from COVID-19 Patients. Testing of virulence of Candida species using Multiplex PCR. T/AgNPs proved highly effective against Candida albicans, Candida kruzei, Candida glabrata and MIC values ranging from 156.25 to 1,250 μg/mL and MFC values ranging from 312.5 to 5,000 μg/mL. The structural and morphological modifications due to T/AgNPs on Candida albicans were detected by TEM. It was highly observed that when Candida albicans cells were subjected to 50 and 100 μg/mL T/AgNPs, a remarkable change in the cell wall and cell membrane was observed.

Combining Essential Oils with Each Other and with Clotrimazole Prevents the Formation of Candida Biofilms and Eradicates Mature Biofilms

Fungal infections by Candida spp. are opportunistic and most often occur in individuals with some predisposing factor. Essential oils (EO) have anti-Candida potential, being a therapeutic alternative to be explored, especially for superficial and mucosal candidiasis. The objective was to analyze the synergistic potential between the EO of Citrus limon, Cupressus sempervirens, Litsea cubeba and Melaleuca alternifolia, and each of them with clotrimazole, to inhibit in vitro the formation and eradication of Candida spp. biofilms. Added to this, the survival of Caenorhabditis elegans was evaluated after exposure to EO, clotrimazole and their synergistic combinations. Anti-Candida activity was determined by microdilution for the substances alone and in EO−EO and EO−clotrimazole combinations. The combinations were performed by the checkerboard method, and the reduction in the metabolic activity of biofilms was determined by the viability of MTT/menadione. C. elegans larvae survival was evaluated after 24 h of exposure to EO, clotrimazole and synergistic combinations. The minimum inhibitory concentration (MIC) of EO ranged from 500 to >4000 µg/mL. The lowest MIC (500 µg/mL) was for C. sempervirens and L. cubeba on a C. krusei isolate; for clotrimazole, the MIC ranged from 0.015 to 0.5 µg/mL. Biofilm inhibition and eradication both ranged from 1000 to >4000 µg/mL. The lethal concentration (LC50) of C. limon, L. cubeba and M. alternifolia was 2000 µg/mL for C. elegans, while for C. sempervirens and clotrimazole, it was not determined within the concentration limits tested. In combination, more than 85% of the larvae survived M. alternifolia−clotrimazole, M. alternifolia−L. cubeba, C. sempervirens−clotrimazole and C. sempervirens−C. limon combinations. This study is the first, to our knowledge, to present a synergistic relationship of EO−EO and EO−clotrimazole combinations on Candida spp. biofilms.

Fungicidal and antibiofilm activities of gold nanoparticles on Candida tropicalis

Aim: To investigate the antifungal activity of two different functionalized gold nanoparticles (AuNP), those stabilized with cetyltrimethylammonium bromide and those conjugated with cysteine, and their effects on the architecture of Candida tropicalis biofilms. Materials & methods: Biofilms were studied by crystal violet binding assay and scanning electron microscopy. We investigated the effects of AuNPs on reactive oxygen species, reactive nitrogen intermediates and enzymatic and nonenzymatic antioxidant defenses. Results/Conclusion: The fungicidal activity and cellular stress of both AuNPs affected biofilm growth through accumulation of reactive oxygen species and reactive nitrogen intermediates. However, cetyltrimethylammonium bromide-stabilized AuNPs revealed a higher redox imbalance. We correlated, for the first time, AuNP effects with the redox imbalance and alterations in the architecture of C. tropicalis biofilms.

Effect of Thymus vulgaris L. essential oil and thymol on the microbiological properties of meat and meat products: A review

Since foodborne diseases are often considered as one of the biggest public health threats worldwide, effective preservation strategies are needed to inhibit the growth of undesirable microorganisms in food commodities. Up to now, several techniques have been adopted for the production of safe and high-quality products. Although the traditional methods can improve the reliability, safety, and shelf-life of food, some of them cannot be applied without rising health concerns. Thereby, the addition of various phytochemicals has gained much attention during the last decades, especially for meat products that may be contaminated with pathogenic and spoilage organisms.

Thyme (Thymus vulgaris L.), as an important medicinal and culinary herb, is a promising source of bioactive compounds that have a great impact on the microbiological stability of meat by suppressing the undesirable microflora. However, the use of these antimicrobials is still facing difficulties due to their aromatic properties and variable efficacy against targeted species.

In this paper, we provide an overview on the potential effects of thyme essential oil (EO) and thymol as bio-preservative agents in meat products. Furthermore, this paper provides insights into the limitations and current challenges of the addition of EOs and their constituents to meat commodities and suggests viable solutions that can improve the applicability of these phytochemicals.

Vapor-Phase of Essential Oils as a Promising Solution to Prevent Candida Vaginal Biofilms Caused by Antifungal Resistant Strains

Background: Vulvovaginal candidiasis (VVC) is a disease with high incidence, a huge impact on the quality of life and health of women, and which represents a great challenge to treat. The growing need to apply antifungal intensive therapies have contributed to an emergence of drug-resistant Candida strains. Thus, effective therapeutic options, to meet the antifungal-resistance challenge and to control high resilient biofilms, are urgently needed. This study aimed to investigate the antifungal activity of essentials oils (EOs) on drug-resistant Candida vaginal isolates. Method: Therefore, the antimicrobial effect of tea tree, niaouli, white thyme, and cajeput EOs on the planktonic growth of Candida isolates was initially evaluated by an agar disc diffusion method. Then, the vapor-phase effect of tea tree EO (VP-TTEO) on biofilm formation and on pre-formed biofilms was evaluated by crystal violet staining, XTT reduction assay, colony forming units’ enumeration, and scanning electron microscopy. Results: The results revealed high antifungal activity of EOs against drug-resistant Candida isolates. Additionally, the VP-TTEO showed a significant inhibitory effect on the biofilm formation of all tested isolates and was able to provoke an expressive reduction in mature Candida albicans biofilms. Conclusions: Overall, this study suggests that the VP-EO may be a promising solution that is able to prevent biofilm-related VVC caused by antifungal-resistant strains.

Petrositis caused by fluconazole-resistant candida: case report and literature review

Background

Petrositis is a rare and fatal complication associated with otitis media. It is most likely caused by bacterial infections, but in some cases it is caused by fungal infections.

Case study

The case in this report is associated with fungal petrositis. The clinical symptoms are: ear pain from chronic otitis media, severe headache, peripheral facial palsy and diplopia. The case was finally confirmed through imaging of middle ear, bacterial culture, pathology, and blood Metagenomic next-generation sequencing (mNGS) test. The patient was treated with sensitive antifungal drugs.

Conclusion

Drug treatment is conservative but efficient method in this case. mNGS can provide pathogenic reference, when antibiotic is not efficient enough for fungal infections or drug-resistant fungal infections cases. This allows we to adjust drug use for the treatment.

Natural Compounds: A Hopeful Promise as an Antibiofilm Agent Against Candida Species

The biofilm communities of Candida are resistant to various antifungal treatments. The ability of Candida to form biofilms on abiotic and biotic surfaces is considered one of the most important virulence factors of these fungi. Extracellular DNA and exopolysaccharides can lower the antifungal penetration to the deeper layers of the biofilms, which is a serious concern supported by the emergence of azole-resistant isolates and Candida strains with decreased antifungal susceptibility. Since the biofilms’ resistance to common antifungal drugs has become more widespread in recent years, more investigations should be performed to develop novel, inexpensive, non-toxic, and effective treatment approaches for controlling biofilm-associated infections. Scientists have used various natural compounds for inhibiting and degrading Candida biofilms. Curcumin, cinnamaldehyde, eugenol, carvacrol, thymol, terpinen-4-ol, linalool, geraniol, cineole, saponin, camphor, borneol, camphene, carnosol, citronellol, coumarin, epigallocatechin gallate, eucalyptol, limonene, menthol, piperine, saponin, α-terpineol, β–pinene, and citral are the major natural compounds that have been used widely for the inhibition and destruction of Candida biofilms. These compounds suppress not only fungal adhesion and biofilm formation but also destroy mature biofilm communities of Candida. Additionally, these natural compounds interact with various cellular processes of Candida, such as ABC-transported mediated drug transport, cell cycle progression, mitochondrial activity, and ergosterol, chitin, and glucan biosynthesis. The use of various drug delivery platforms can enhance the antibiofilm efficacy of natural compounds. Therefore, these drug delivery platforms should be considered as potential candidates for coating catheters and other medical material surfaces. A future goal will be to develop natural compounds as antibiofilm agents that can be used to treat infections by multi-drug-resistant Candida biofilms. Since exact interactions of natural compounds and biofilm structures have not been elucidated, further in vitro toxicology and animal experiments are required. In this article, we have discussed various aspects of natural compound usage for inhibition and destruction of Candida biofilms, along with the methods and procedures that have been used for improving the efficacy of these compounds.

Recent Advances in the Application of Essential Oils as Potential Therapeutic Candidates for Candida-Related Infections

Candidiasis (oral, vulvovaginal, or systemic bloodstream infections) are important human fungal infections associated with a high global prevalence in otherwise healthy adults but are also opportunistic infections in immunocompromised patients. With the recent discovery of the multidrug resistant—and often difficult to treat—Candida auris, as well as the rising costs associated with hospitalisations and the treatment of infections caused by Candida species, there is an urgent need to develop effective therapeutics against these pathogenic yeasts. Essential oils have been documented for many years as treatments for different ailments and are widely known and utilised in alternative and complementary therapies, including treating microbial infections. This review highlights knowledge from research on the effects of medicinal plants, and in particular, essential oils, as potential treatments against different Candida species. Studies have been evaluated that describe the experimental approaches used in investigating the anticandidal effects of essential oils (in vivo and in vitro), the established mode of action of the different compounds against different Candida species, the effect of a combination of essential oils with other compounds as potential therapies, and the evidence from clinical trial studies.

Phytotherapy: A Solution to Decrease Antifungal Resistance in the Dental Field

The pathologies produced by fungi in the oral cavity in recent decades have become a health problem, with factors such as an imbalance of the local microbiota being the cause for their propagation. Conventional antifungal treatments, instead of being beneficial, have generated alterations that have led to antifungal resistance. The aim of this study was to investigate and describe phytotherapy resources as a possible solution to oral antifungal resistance. A bibliographic search was carried out on platforms such as PubMed, Scopus, ScienceDirect, Web of Science, and Google scholar. A total of 248 scientific articles were obtained, of which 108 met the inclusion criteria. Microorganisms of fungal origin currently show resistance to the different antifungals of conventional use, which is undoubtedly altering the oral health of human beings, but there are new therapeutic possibilities such as the active principles of various natural species.

Antifungal effect of a new photosensitizer derived from BODIPY on Candida albicans biofilms

BACKGROUND

Photodynamic therapy (PDT) has been recognized as an alternative treatment of Candida albicans (C. albicans) infections. The aim of this study was to investigate the antifungal effect of PDT mediated by a new photosensitizer (PS) derived from BODIPY (BDP-4L) on C. albicans biofilms.

METHODS

C. albicans biofilms were incubated with BDP-4L of different concentrations and then irradiated at the light doses of 1.8, 3.6, 5.4, 7.2 and 9.0 J/cm². XTT reduction assay was conducted to determine the PS concentration and PDT parameters. Confocal light scanning microscopy (CLSM) and scanning electron microscope (SEM) were used to visualize and quantify the effect of BDP-4L on C. albicans biofilms after PDT.

RESULTS

C. albicans biofilms were inactivated in light dose-dependent and PS concentration-dependent manners using BDP-4L as PS. Without irradiation, no inactivation effect was observed when PS concentrations varied from 5 μM to 80 μM. 40 μM PS with 3.6 J/cm² irradiation resulted in a significant reduction of 83.8% in biofilm metabolic activities. CLSM assay demonstrated that cell viability was obviously inhibited by 82.6%. SEM images revealed ruptured and rough cell surface, indicating increased cell membrane permeability after PDT.

CONCLUSIONS

Our results suggested that BDP-4L mediated PDT exhibited a favorable antifungal effect on C. albicans biofilms.

A Focused Insight into Thyme: Biological, Chemical, and Therapeutic Properties of an Indigenous Mediterranean Herb

A perennial wild shrub from the Lamiaceae family and native to the Mediterranean region, thyme is considered an important wild edible plant studied for centuries for its unique importance in the food, pharmaceutical, and cosmetic industry. Thyme is loaded with phytonutrients, minerals and vitamins. It is pungent in taste, yet rich in moisture, proteins, crude fiber, minerals and vitamins. Its chemical composition may vary with geographical location but is mainly composed of flavonoids and antioxidants. Previous studies have illustrated the therapeutic effects of thyme and its essential oils, especially thymol and carvacrol, against various diseases. This is attributed to its multi-pharmacological properties that include, but are not limited to, antioxidant, anti-inflammatory, and antineoplastic actions. Moreover, thyme has long been known for its antiviral, antibacterial, antifungal, and antiseptic activities, in addition to remarkable disruption of microbial biofilms. In the COVID-19 era, some thyme constituents were investigated for their potential in viral binding. As such, thyme presents a wide range of functional possibilities in food, drugs, and other fields and prominent interest as a nutraceutical. The aims of the current review are to present botanical and nutritive values of this herb, elaborate its major constituents, and review available literature on its dietetic and biological activities.

Antimicrobial Mechanisms of Enterocin CHQS Against Candida albicans

Candida albicans is the most common fungal pathogen in hospital-acquired infections, which is extremely harmful to health. The increasing fungal infections is requiring the rapid development of novel antifungal agents. In this study, the antimicrobial activity of CHQS, an enterocin isolated from Enterococcus faecalis TG2 against C. albicans was confirmed by the minimum inhibitory concentration, minimum fungicidal concentration, and time-kill curve. Aniline blue and calcofluor white staining methods showed that CHQS remarkably affected β-1,3-glucan and chitin cell wall components and made cell wall more vulnerable. The C. albicans cell wall rupture and intracellular vacuolation were observed by TEM and SEM. Moreover, CHQS induced the accumulation of intracellular reactive oxygen species and decreased mitochondrial membrane potential. These results suggested that CHQS might have a complex multi-target antimicrobial mechanism against C. albicans. In addition, the use of CHQS combined with amphotericin B showed synergistic antimicrobial effects against C. albicans. In conclusion, enterocin CHQS, a natural product with antimicrobial effect, might has a bright future for the development of new antifungal drugs.

Antifungal and anti-virulence activity of six essential oils against important Candida species - a preliminary study

Opportunistic infections with Candida species are becoming more problematic, considering their increasing virulence and resistance to antifungal drugs.

AIM

To assess the antifungal and anti-virulence activity of basil, cinnamon, clove, melaleuca, oregano and thyme essential oils (EOs) on five Candida species (C. albicans, C. auris, C. krusei C. parapsilosis and C. guillermondii).

METHODS

The MIC, growth rate, antibiofilm activity, regulation of gene expression (ALS3, SAP2, HSP70) and germ-tube formation were evaluated by specific methods.

RESULTS

Most EOs inhibited Candida species growth and reduced the expression of some virulence factors. Cinnamon and clove EO showed the most significant inhibitory effects.

CONCLUSIONS

The tested EOs are promising agents for facilitating the management of some Candida infections.

One step green synthesis of Cu nanoparticles by the aqueous extract of Juglans regia green husk: assessing its physicochemical, environmental and biological activities

Juglans regia (J. regia) green husk is an abundant agricultural waste. In this study, an economical, rapid and green synthetic route was introduced for the biosynthesis of copper nanoparticles (CuNPs) by applying the aqueous extract of J. regia green husk at the ambient conditions. Ultra Violet-Visible (UV-Visible) analysis revealed that the Surface Plasmon Resonance (SPR) of the CuNP was 212 nm. The average hydrodynamic and metallic core diameters of the CuNPs were about 53-28 nm, respectively. X-ray Diffraction (XRD) analysis presented that the CuNPs were amorphous. The CuNPs exhibited the highest free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging efficiency. These nanoparticles (NPs) showed antibacterial, antifungal and antibiofilm properties. They presented photocatalytic activity against Methyl Orange (MO). Besides, the potential of these NPs for the fast and precise colorimetric detection of Hg²⁺ was remarkable. The biosynthesized CuNPs are introduced as a multifunctional nanomaterial with various applications in medicine and environmental cases. The CuNPs were produced through an environmentally green process by the aqueous extract of dried J. regia green husk at the ambient condition. The CuNPs confirmed that this type of nanomaterial is a multifunctional agent with significant antibacterial, antifungal, antibiofilm, antioxidant, photocatalytic activities. Besides, it is a promising colorimetric sensor for the detection of Hg²⁺ in an aqueous complex media.

The combination of hexanal and geraniol in sublethal concentrations synergistically inhibits Quorum Sensing of Pseudomonas fluorescens - in vitro and in silico approaches

AIM

Hexanal and geraniol are essential oil components with anti-Quorum Sensing (QS) activity against Pseudomonas fluorescens. This study demonstrated that QS inhibition (QSI) efficacy of hexanal and geraniol combination (HG) was significantly increased compared with their mono-counterparts at the same concentration.

METHODS AND RESULTS

Tests on P. fluorescens motility, biofilm formation, acyl-homoserine lactones (AHLs) production, gene expression in vitro, and molecular docking in silico were conducted to evaluate the synergistic effect of hexanal and geraniol on QSI. HG mixture at 0.5 minimal inhibitory concentration (MIC) showed a strong synergistic inhibition of biofilm formation (51.8%), motility (60.13%), and extracellular protease activity (58.9%) of P. fluorescens. The synthesis of AHLs, e.g. C₈ -HSL and C₁₂ -HSL was inhibited by hexanal, geraniol, and HG; both AHLs are responsible for regulating virulence factors in P. fluorescens. The expression of pcoI and gacA genes regulating AHLs synthetase and sensor kinase was significantly down-regulated by HG (0.29 and 0.38-fold) at 0.5 MIC. Hexenal and HG showed significant inhibition of pcoR and gacS genes expression regulating AHLs receptor protein and response regulator; however, geraniol failed to down-regulate the two genes. Molecular docking in silico also supported these findings. Hexenal inserted into minor groove of pcoI/pcoR DNA fragments to inhibit genes expression. Both hexanal (-31.487 kcal/mol) and geraniol (-25.716 kcal/mol) had a higher binding affinity with PcoI protein than halogenated furanone C30 (-24.829 kcal/mol) as a known competitor of AHLs. Similarly, hexenal and geraniol would also strongly bind to the PcoR protein.

CONCLUSIONS

It was found that HG at 0.5 MIC would effectively inhibit QS through suppressing pcoR/gacS and gacA/gacS genes expression and therefore, inhibit motility and biofilm formation in P. fluorescens.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study indicated that HG at sub-MIC as QS inhibitor could be further developed as a new preservative of agri-food products.

Susceptibility of Fluconazole-Resistant Candida albicans to Thyme Essential Oil

Candida spp. is the most common microbial pathogen in fungal infections. There has been a tremendous increase in cases of candidiasis, especially among critically ill non-neutropenic patients. Candida albicans’ isolates were procured from the Prince Sultan Military Hospital, Riyadh, KSA. The isolates were characterized for their identification using CHROMagar, carbohydrate metabolism, germ tube formation, and RAPD-PCR techniques. The essential oil of Thymus vulgaris was obtained by hydro-distillation and characterized to decipher the major bioactive phytoconstituents. The antifungal activity of the thyme essential oil (TEO) was evaluated against fluconazole-resistant C. albicans isolates. The major phytocomponents identified by GC/MS were thymol (68.1%) followed by γ-terpinene (8.9%), cymol (7.7%), caryophyllene (1.1%), linalool (1.4%). The TEO successfully reduced the growth of C. albicans isolates. At very low doses, the TEO proved to be fungi static and fungicidal. TEO also effectively inhibited the germ tube formation and budging of fungal pathogens. The time kill assays have shown that TEO was more effective against drug resistant clinical isolates than fluconazole. This study provides an array of experimental evidence regarding the therapeutic efficacy of TEO against the drug-resistant clinical isolates of C. albicans. The findings may be used in the development of a new antifungal agent accordingly.

Chromatographic profiles and antimicrobial activity of the essential oils obtained from some species and cultivars of the Mentheae tribe (Lamiaceae)

The present study was focused on the chemical composition and antimicrobial activity of the essential oils (EsO) obtained from five Lamiaceae representatives grown in the south of Ukraine. Among them are Salvia sclarea L., Monarda didyma (cultivar ‘Cambridge Scarlet’), Thymus pulegioides (cultivar ‘2/6-07’), Thymus vulgaris (cultivar ‘Jalos’), and Thymus serpyllum L. The component analysis of the EsO was carried out by gas chromatography method coupled with mass spectrometry (GC–MS). The antimicrobial properties of the EsO were determined using the agar diffusion test against widespread pathogenic bacterial strains (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Streptococcus pyogenes) and opportunistic yeast Candida albicans. The EsO of Thymus serpyllum and Thymus vulgaris (cultivar ‘Jalos’) displayed noteworthy antibacterial properties against a wide spectrum of the microorganisms. These antimicrobial properties could be attributed to the high content of aromatic monoterpenoid thymol (52.56% and 47.33%, respectively). The EsO of Salvia sclarea with the dominance of linalyl acetate (45.51%) and linalool (38.98%) as well as Thymus pulegioides (cultivar ‘2/6-07’) containing α-citral (27.10%) and β-citral (17.11%) demonstrated the strongest antimicrobial effects on typical and clinical strains of Staphylococcus aureus with the inhibition zones in the range of 24.0–31.0 mm. The Salvia sclarea EsO demonstrated the most significant effect against clinical strains of Candida albicans. In conclusion, the present study revealed the chemical composition of five Lamiaceae species and cultivars grown in the south of Ukraine and considerable antimicrobial activity of the tested EsO, especially against the typical and clinical strains of Staphylococcus aureus and Candida albicans. The obtained results could be perspective for applying in the pharmaceutical industry and for the conservation of food and cosmetic products.

In vitro and in vivo analysis of monotherapy and dual therapy with ethyl caffeate and fluconazole on virulence factors of Candida albicans and systemic candidiasis

OBJECTIVES

Candida albicans is the most clinically prevalent cause of systemic fungal infections in the immunocompromised population. The biofilm-forming ability of C. albicans confers resistance to conventional antifungal agents. The main aim of this study was to investigate the antifungal effects of ethyl caffeate (EC) alone and in combination with fluconazole (FLU) against C. albicans isolates.

METHODS

The single and combined antifungal activities of EC and FLU were evaluated against planktonic and biofilm cells of C. albicans by the checkerboard assay, time-kill test, crystal violet assay, live/dead staining, rhodamine 6G (R6G) efflux analysis and hydrolase activity. Monotherapy and dual therapy of EC and FLU against systemic candidiasis in a mouse model was also evaluated.

RESULTS

The results showed that EC+FLU displayed synergism in 14/26 planktonic C. albicans isolates and 11/26 C. albicans biofilms with fractional inhibitory concentration index (FICI) values ranging between 0.06-0.49 and 0.02-0.38, respectively. Compared with monotherapy, the combination of EC+FLU can markedly inhibit adhesion, yeast-to-hyphae transition, premature and mature biofilm metabolism, hydrolase secretion and drug efflux function of C. albicans Z1407 and Z4935. Moreover, EC can potentiate the antifungal activity of FLU to improve mouse survival, reduce fungal burden and alleviate pathological damage in both C. albicans isolates compared with EC or FLU used alone.

CONCLUSION

EC exhibits a moderate antifungal potential but can be a strong synergist with FLU against C. albicans, highlighting the potential of EC in clinical antifungal therapy as a sensitiser.