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11 pages, 1183 KiB

Open AccessArticle

Metabolic Stress Induced by Quercetin Enhances Dormancy and Persistence in Staphylococcus aureus

by Dae-Youn Kim and Tae-Jong Kim

Antibiotics 2025, 14(5), 424; https://doi.org/10.3390/antibiotics14050424 - 22 Apr 2025

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Abstract

Background/Objectives: The persistence of Staphylococcus aureus poses a significant challenge in clinical treatments because of its ability to withstand antibiotic therapy. This study assessed the role of quercetin in promoting bacterial dormancy and persistence through ATP depletion and revealed its potential impact [...] Read more.

Background/Objectives: The persistence of Staphylococcus aureus poses a significant challenge in clinical treatments because of its ability to withstand antibiotic therapy. This study assessed the role of quercetin in promoting bacterial dormancy and persistence through ATP depletion and revealed its potential impact on antibiotic tolerance. Methods: To assess the effects of quercetin on bacterial metabolism and persistence, S. aureus cultures were treated with quercetin, and intracellular ATP levels were then measured. The effect of quercetin on persister cell formation was assessed using antibiotic exposure assays, including pre-treatment and post-treatment strategies. Results: Quercetin treatment significantly depleted intracellular ATP levels in a dose-dependent manner, suggesting the presence of metabolic stress. This ATP depletion correlated with increased persister cell formation across multiple antibiotic treatments, indicating that quercetin-induced dormancy enhances bacterial persistence. Notably, quercetin pre-treatment further increased persister cell counts, while delayed quercetin administration increased persister cell survival, highlighting the influence of the timing of metabolic stress on persistence outcomes. Conclusions: Quercetin promotes bacterial persistence by inducing ATP depletion and metabolic dormancy. Although quercetin’s bactericidal properties may initially impair bacterial growth, its potential to enhance persistence underscores the complexity of its effects. Further research is necessary to determine optimal strategies for harnessing the antimicrobial properties of quercetin while minimizing its persistence-promoting effects. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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13 pages, 1356 KiB

Open AccessArticle

The Therapeutic Potential of West Indian Lemongrass (Cymbopogon citratus) Essential Oil-Based Ointment in the Treatment of Pitted Keratolysis

by György Schneider, Bettina Schweitzer, Anita S. Steinbach, Ágnes S. Hodován, Marianna Horváth, Eszter Bakó, Anna Mayer and Szilárd Pál

Antibiotics 2025, 14(3), 241; https://doi.org/10.3390/antibiotics14030241 - 27 Feb 2025

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Abstract

Background: Due to their antibacterial activities, essential oils can be potential alternatives to antibiotics in certain cases. West Indian lemongrass (Cymbopogon citratus) essential oil (LEO) is effective against a broad range of bacteria by inhibiting spore formation, and is considered safe. [...] Read more.

Background: Due to their antibacterial activities, essential oils can be potential alternatives to antibiotics in certain cases. West Indian lemongrass (Cymbopogon citratus) essential oil (LEO) is effective against a broad range of bacteria by inhibiting spore formation, and is considered safe. In this study, we demonstrated its therapeutical potential in the treatment of pitted keratolysis (PK), a superficial skin infection affecting the pressure-bearing areas of plantar surfaces. Methods: For in vitro antibacterial efficacy testing, LEO was mixed into different ointment bases, including Hydrogelum methylcellulose FoNo VIII., Ungentum oleosum FoNo VIII. (Ung. oleoso), Unguentum stearini FoNo VIII. (Ung. stearin), and Vaselinum cholesterinatum FoNo VIII. (Vasel. cholest.), at different concentrations of 1, 3, and 5%. These formulations were tested on representatives of three bacterial species associated with PK: Kytococcus sedentarius, Dermatophilus congolensis, and Bacillus thuringiensis. Results: In the in vitro tests, Hydrogelum methylcellulose (HM) gel best supported the antibacterial effects of LEO, reducing the number of living bacteria on agar plates by 4–5 orders of magnitude in a concentration-dependent manner during the 30 min exposure times. This was also confirmed by the Franz diffusion cell drug release test; after 30 min, several active compounds could be detected in the HM samples, in contrast to the other bases. Shelf-life experiments showed that the HM base supported the antibacterial features of 3% LEO for at least 2 years without significant loss of efficacy. Conclusions: Our study highlights that ointments containing essential oils potentially have a place in the treatment of PK. Therefore, antibiotics may potentially be replaced for the treatment of PK, thereby reducing environmental antibiotic pressure, which is one of the driving forces behind the spread of antibiotic resistance. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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14 pages, 622 KiB

Open AccessArticle

Biological Activity and Chemical Composition of Essential Oil from Leaves and Fruits of Zanthoxylum mantaro (J.F.Macbr.) J.F.Macbr

by Vladimir Morocho, Odalis Eras, Teresa Rojas, Britany Jiménez, María Fernanda Roa and Luis Cartuche

Antibiotics 2025, 14(3), 216; https://doi.org/10.3390/antibiotics14030216 - 21 Feb 2025

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Abstract

Objective: In this study, the chemical composition and biological activities of the essential oils extracted from the leaves and fruits of Zanthoxylum mantaro were analyzed. Methods: The essential oils were obtained through hydrodistillation using a Clevenger-type apparatus. Chemical composition was determined by [...] Read more.

Objective: In this study, the chemical composition and biological activities of the essential oils extracted from the leaves and fruits of Zanthoxylum mantaro were analyzed. Methods: The essential oils were obtained through hydrodistillation using a Clevenger-type apparatus. Chemical composition was determined by gas chromatography coupled with mass spectrometry (GC-MS) and gas chromatography with a flame ionization detector (GC-FID). The antimicrobial activity was evaluated against four Gram-positive bacteria, three Gram-negative bacteria, and two fungi using the broth microdilution method. Antioxidant activity was assessed using the ABTS (2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assays. Additionally, the acetylcholinesterase inhibitory effect of the essential oils was measured by a spectrophotometric method. Results and Conclusions: A total of 23 compounds were identified in the essential oil from the fruits, while 47 compounds were found in the essential oil from the leaves. The major constituents of the fruit essential oil were α-thujone (39.85%), β-thujone (25.04%), sabinene (10.71%), and terpinen-4-ol (4.38%), whereas the main compounds in the leaf essential oil were germacrene D (21.75%), nerolidol (E) (12.39%), and pentadecanal (7.14%). The essential oil from the fruits exhibited antifungal activity against Aspergillus niger (ATCC 6275), with a minimum inhibitory concentration (MIC) of 1000 μg/mL. Both the fruit and leaf essential oils showed moderate antioxidant activity in the ABTS assay, with SC₅₀ values of 274.14 ± 1.06 μg/mL and 2798.85 ± 15.69 μg/mL, respectively. Furthermore, the fruit essential oil demonstrated considerable acetylcholinesterase inhibitory activity with an IC₅₀ value of 65.46 ± 1.01 μg/mL, while the leaf essential oil exhibited an IC₅₀ value of 158.2 ± 1.02 μg/mL. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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15 pages, 1614 KiB

Open AccessArticle

Integrating Metabolomics and Genomics to Uncover Antimicrobial Compounds in Lactiplantibacillus plantarum UTNGt2, a Cacao-Originating Probiotic from Ecuador

by Diana Molina, Evelyn Angamarca, George Cătălin Marinescu, Roua Gabriela Popescu and Gabriela N. Tenea

Antibiotics 2025, 14(2), 123; https://doi.org/10.3390/antibiotics14020123 - 24 Jan 2025

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Abstract

Background/Objectives: Lactic acid bacteria (LAB) produce several diverse metabolites during fermentation that play key roles in enhancing health and food quality. These metabolites include peptides, organic acids, exopolysaccharides, and antimicrobial compounds, which contribute to gut health, immune system modulation, and pathogen inhibition. [...] Read more.

Background/Objectives: Lactic acid bacteria (LAB) produce several diverse metabolites during fermentation that play key roles in enhancing health and food quality. These metabolites include peptides, organic acids, exopolysaccharides, and antimicrobial compounds, which contribute to gut health, immune system modulation, and pathogen inhibition. This study analyzed the intracellular (Met-Int) and extracellular metabolites (Met-Ext-CFS; cell-free supernatant) of Lactiplantibacillus plantarum UTNGt2, a probiotic strain isolated from Theobroma grandiflorum. Methods: The assessment was performed using capillary LC-MS/MS metabolomics with a SWATH-based data-independent acquisition approach to identify molecules associated with antimicrobial activity. Results: The integration of metabolomic data with whole-genome annotation enabled the identification of several key metabolites, including amino acids, nucleotides, organic acids, oligopeptides, terpenes, and flavonoids, many of which were associated with the antimicrobial activity of UTNGt2. Pathway analysis reveals critical processes such as secondary metabolite biosynthesis, nucleotide and galactose metabolism, and cofactor biosynthesis. By integrating RiPP (ribosomally synthesized and post-translationally modified peptide) cluster gene predictions with LC-MS data, this study validates the production of specific RiPPs and uncovers novel bioactive compounds encoded within the UTNGt2 genome. The oligopeptide val-leu-pro-val-pro-gln found in both Met-Int (ESI+) and Met-Ext-CFS (ESI+) may contribute to the strain’s antimicrobial strength. It could also enhance probiotic and fermentation-related functions. Conclusions: While genome-based predictions highlight the strain’s biosynthetic potential, the actual metabolite profile is influenced by factors like transcriptional regulation, post-transcriptional and post-translational modifications, and environmental conditions. These findings emphasize the value of multi-omics approaches in providing a holistic understanding of metabolite production and its role in antimicrobial activity. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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18 pages, 3963 KiB

Open AccessArticle

Vismia guianensis Improves Survival of Tenebrio molitor and Mice During Lethal Infection with Candida albicans

by Arthur André Castro Costa, Elizangela Pestana Motta, Aluísio Silva Oliveira, Pamela Gomes Santos, Josivan Regis Farias, Danielle Cristine Gomes Franco, Mayara Cristina Pinto Silva, Nicolle Teixeira Barbosa, Simone Batista Muniz, Luís Douglas Miranda. Silva, Lucilene Amorim Silva, Claudia Quintino Rocha, Flavia Raquel Fernandes Nascimento and Rosane Nassar Meireles Guerra

Antibiotics 2025, 14(1), 72; https://doi.org/10.3390/antibiotics14010072 - 11 Jan 2025

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Abstract

Background/Objectives: Vismia guianensis is a vegetal species popularly used to treat fungal infections. This study evaluated the anti-Candida effect of V. guianensis extract after C. albicans lethal infection in Tenebrio molitor larvae and mice. Methods and Results: The chemical profile [...] Read more.

Background/Objectives: Vismia guianensis is a vegetal species popularly used to treat fungal infections. This study evaluated the anti-Candida effect of V. guianensis extract after C. albicans lethal infection in Tenebrio molitor larvae and mice. Methods and Results: The chemical profile analysis of a hydroethanolic extract of the leaves of V. guianensis (EHVG) identified 14 compounds. Two sets of experiments used T. molitor larvae. To evaluate toxicity, the uninfected larvae were treated with EHVG or anthraquinone. We considered the following groups: the controls received PBS; ANFO B received amphotericin B (600 mg/mL); EHVG received the extract; and ANTQ received anthraquinone. The extract and anthraquinone resulted in low-level toxicity in the T. molitor larvae. Another set of experiments evaluated the EHVG effect during lethal infection with Candida albicans. The T. molitor larvae were treated intracelomically (ic/10 μL). Treatment with EHVG efficiently improved the survival of the larvae after lethal infection (60%), probably due to the reduction in CFUs. In the mice, the antifungal effect of EHVG was determined in three groups of immunosuppressed Swiss mice (cyclophosphamide, 50 mg/kg/ip) infected with C. albicans (1 × 10⁷ CFU/ip). The control animals were infected and untreated; the ANFO B animals were infected and treated with amphotericin B (600 µg/kg/ip); and the EHVG animals were infected and treated with the extract (5 mg/kg/orally). A SHAM group (uninfected and untreated) was also included. Survival was assessed for 5 days. The extract increased the mice’s survival (60%) and life expectancy, reducing the CFU counts in the peritoneum and blood. EHVG also increased the number of blood neutrophils and peritoneal macrophages. These systemic activities are likely associated with the presence of flavonoids in the extract. Conclusions: The beneficial effects of EHVG in lethal sepsis are related to an antifungal effect, with the number of CFUs decreasing in the larvae and the mice. In addition, EHVG showed immunological activity in the mice, considering immune cell distribution and cytokine production. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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19 pages, 4130 KiB

Open AccessArticle

Identification and Bioactivity Analysis of a Novel Bacillus Species, B. maqinnsis sp. nov. Bos-x6-28, Isolated from Feces of the Yak (Bos grunniens)

by Qiang Ma, Xin Xiang, Yan Ma, Guangzhi Li, Xingyu Liu, Boai Jia, Wenlin Yang, Hengxia Yin and Benyin Zhang

Antibiotics 2024, 13(12), 1238; https://doi.org/10.3390/antibiotics13121238 - 23 Dec 2024

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Abstract

Background: The identification of novel bacterial species from the intestines of yaks residing on the Qinghai–Tibet Plateau is pivotal in advancing our understanding of host–microbiome interactions and represents a promising avenue for microbial drug discovery. Methods: In this study, we conducted a polyphasic [...] Read more.

Background: The identification of novel bacterial species from the intestines of yaks residing on the Qinghai–Tibet Plateau is pivotal in advancing our understanding of host–microbiome interactions and represents a promising avenue for microbial drug discovery. Methods: In this study, we conducted a polyphasic taxonomic analysis and bioactive assays on a Bacillus strain, designated Bos-x6-28, isolated from yak feces. Results: The findings revealed that strain Bos-x6-28 shares a high 16S rRNA gene sequence similarity (98.91%) with B. xiamenensis HYC-10^T and B. zhangzhouensis DW5-4^T, suggesting close phylogenetic affinity. Physiological and biochemical characterizations demonstrated that Bos-x6-28 could utilize nine carbon sources, including D-galactose, inositol, and fructose, alongside nine nitrogen sources, such as threonine, alanine, and proline. Analysis of biochemical markers indicated that Bos-x6-28’s cell wall hydrolysates contained mannose, glucose, and meso-2,6-diaminopimelic acid, while menaquinone-7 (MK-7), phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylglycerol (DPG) were found in the cell membrane. The primary cellular fatty acids included C16:0 (28.00%), cyclo-C17:0 (19.97%), C14:0 (8.75%), cyclo-C19:0 (8.52%), iso-C15:0 (5.49%), anteiso-C15:0 (4.61%), and C12:0 (3.15%). Whole-genome sequencing identified a genome size of 3.33 Mbp with 3353 coding genes. Digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) analyses confirmed Bos-x6-28 as a novel species, hereby named B. maqinnsis Bos-x6-28 (MCCC 1K09379). Further genomic analysis unveiled biosynthetic gene clusters encoding bioactive natural compounds, including β-lactones, sactipeptides, fengycin, and lichenysin analogs. Additionally, in vitro assays demonstrated that this strain exhibits antibacterial and cytotoxic activities. Conclusions: These findings collectively indicate the novel Bacillus species B. maqinnsis Bos-x6-28 as a promising source for novel antibiotic and antitumor agents. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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20 pages, 3131 KiB

Open AccessArticle

Ellagic Acid Potentiates the Inhibitory Effects of Fluconazole Against Candida albicans

by Amanda Graziela Gonçalves Mendes, Carmem Duarte Lima Campos, José Lima Pereira-Filho, Aleania Polassa Almeida Pereira, Gabriel Silva Abrantes Reis, Árlon Wendel de Marinho Silva Araújo, Pablo de Matos Monteiro, Flávia Castello Branco Vidal, Silvio Gomes Monteiro, Isabella Fernandes da Silva Figueiredo, Elizabeth Soares Fernandes, Cristina de Andrade Monteiro and Valério Monteiro-Neto

Antibiotics 2024, 13(12), 1174; https://doi.org/10.3390/antibiotics13121174 - 4 Dec 2024

Cited by 2 | Viewed by 1066

Abstract

Background/Objectives: Antifungal resistance to azoles, coupled with the increasing prevalence of Candida albicans infections, represents a significant public health challenge and has driven the search for new natural compounds that can act as alternatives or adjuvants to the current antifungals. Ellagic acid (EA) [...] Read more.

Background/Objectives: Antifungal resistance to azoles, coupled with the increasing prevalence of Candida albicans infections, represents a significant public health challenge and has driven the search for new natural compounds that can act as alternatives or adjuvants to the current antifungals. Ellagic acid (EA) has demonstrated antifungal activity; however, its effects are not fully understood. In this study, we investigated the in vitro anti-Candida activity of EA and its ability to potentiate the effects of fluconazole (FLZ) on C. albicans. Methods: The Minimum Inhibitory Concentration (MIC) of EA was determined by broth microdilution and its interaction with FLZ was assessed using a checkerboard assay. Additionally, we examined the effects of EA on yeast-to-hypha transition, inhibition of biofilm formation, time–kill kinetics, hemolytic activity, and cytotoxicity in HeLa ATCC^® CCL-2™ cells. Results: EA exhibited MIC values ranging from 250 to 2000 µg/mL and showed synergistic and additive interactions with FLZ, resulting in a marked reduction in the MIC values of FLZ (up to 32-fold) and EA (up to 16-fold). In the time–kill assay, the most effective combinations were 4× EA MIC, 2× EA MIC, and FIC EA + FLZ, which showed fungicidal activity. Furthermore, EA did not show hemolytic activity and demonstrated low and dose-dependent cytotoxicity in HeLa cells, with no cytotoxic effects observed in combination with FLZ. EA and the synergistic combination of EA and FLZ interfered with both the yeast-to-hypha transition process in C. albicans cells and biofilm formation. In addition to its antifungal efficacy, EA demonstrated a favorable safety profile at the concentrations used. Conclusions: This study presents promising results regarding the potential use of EA in combination with FLZ for the treatment of C. albicans infections. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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23 pages, 6586 KiB

Open AccessArticle

Studies Regarding Antimicrobial Properties of Some Microbial Polyketides Derived from Monascus Strains

by Daniela Albisoru, Nicoleta Radu, Lucia Camelia Pirvu, Amalia Stefaniu, Narcisa Băbeanu, Rusandica Stoica and Dragos Paul Mihai

Antibiotics 2024, 13(11), 1092; https://doi.org/10.3390/antibiotics13111092 - 16 Nov 2024

Cited by 1 | Viewed by 1356

Abstract

Finding new molecules to prevent the growth of antimicrobial resistance is a hot topic for scientists worldwide. It has been reported that some raw bioproducts containing Monascus polyketides have antimicrobial activities, but extensive studies on this effect have not been conducted. In this [...] Read more.

Finding new molecules to prevent the growth of antimicrobial resistance is a hot topic for scientists worldwide. It has been reported that some raw bioproducts containing Monascus polyketides have antimicrobial activities, but extensive studies on this effect have not been conducted. In this context, our studies aimed to evaluate the antimicrobial properties of six raw bioproducts containing three classes of microbial polyketides biosynthesized by three Monascus strains through solid-state biosynthesis. As a methodology, we performed in silico predictions using programs such as PyMOL v3.0.4 and employed ESI-MS techniques to provide evidence of the presence of the six studied compounds in our bioproducts. The results obtained in silico were validated through in vitro studies using the Kirby-Bauer diffusion method on bacteria and fungi. The test performed in silico showed that Monascorubramine has the highest affinity for both Gram-positive and Gram-negative bacteria, followed by yellow polyketides such as Ankaflavin and Monascin. The estimated pharmacokinetic parameters indicated high gastrointestinal absorption and the potential to cross the blood-brain barrier for all studied compounds. However, the compounds also inhibit most enzymes involved in drug metabolism, presenting some level of toxicity. The best in vitro results were obtained for S. aureus, with an extract containing yellow Monascus polyketides. Predictions made for E. coli were validated in vitro for P. aeruginosa, S. enterica, and S. marcescens, as well as for fungi. Significant antibacterial properties were observed during this study for C. albicans, S. aureus, and fungal dermatophytes for crude bioproducts containing Monascus polyketides. In conclusion, the antimicrobial properties of Monascus polyketides were validated both in silico and in vitro. However, due to their potential toxicity, these bioproducts would be safer to use as topical formulations. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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15 pages, 3630 KiB

Open AccessArticle

Anti-Biofilm Action of Cineole and Hypericum perforatum to Combat Pneumonia-Causing Drug-Resistant P. aeruginosa

by Sourav Chakraborty, Piyush Baindara, Pralay Sharma, Austin Jose T, Kumaravel V, Raja Manoharan and Santi M. Mandal

Antibiotics 2024, 13(8), 689; https://doi.org/10.3390/antibiotics13080689 - 24 Jul 2024

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Abstract

Hospital-acquired antibiotic-resistant pneumonia is one of the major causes of mortality around the world that pose a catastrophic threat. Pseudomonas aeruginosa is one of the most significant opportunistic pathogens responsible for hospital-acquired pneumonia and gained resistance to the majority of conventional antibiotics. There [...] Read more.

Hospital-acquired antibiotic-resistant pneumonia is one of the major causes of mortality around the world that pose a catastrophic threat. Pseudomonas aeruginosa is one of the most significant opportunistic pathogens responsible for hospital-acquired pneumonia and gained resistance to the majority of conventional antibiotics. There is an urgent need for antibiotic alternatives to control drug-resistant pneumonia and other related respiratory infections. In the present study, we explored the antibacterial potential of cineole in combination with homeopathic medicines against biofilm-forming drug-resistant P. aeruginosa. Out of 26 selected and screened homeopathic medicines, Hypericum Perforatum (HyPer) was found to eradicate biofilm-forming drug-resistant P. aeruginosa most effectively when used in combination with cineole. Interestingly, the synergistic action of HyPer and cineole was also found to be similarly effective against planktonic cells of P. aeruginosa. Further, the potential synergistic killing mechanisms of cineole and HyPer were determined by analyzing zeta membrane potential, outer membrane permeability, and DNA release from P. aeruginosa cells upon treatment with cineole and HyPer. Additionally, molecular docking analysis revealed strong binding affinities of hypericin (an active ingredient of HyPer) with the PqsA (a quorum sensing protein) of P. aeruginosa. Overall, our findings revealed the potential synergistic action of cineole and HyPer against biofilm-forming drug-resistant P. aeruginosa. Cineole and HyPer could be used in combination with other bronchodilators as inhalers to control the biofilm-forming drug-resistant P. aeruginosa. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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17 pages, 3725 KiB

Open AccessArticle

Artemisinin May Disrupt Hyphae Formation by Suppressing Biofilm-Related Genes of Candida albicans: In Vitro and In Silico Approaches

by Esra Sumlu, Merve Aydin, Emine Nedime Korucu, Saliha Alyar and Ahmed Moustapha Nsangou

Antibiotics 2024, 13(4), 310; https://doi.org/10.3390/antibiotics13040310 - 28 Mar 2024

Cited by 1 | Viewed by 2902

Abstract

This study aimed to assess the antifungal and antibiofilm efficacy of artemisinin against Candida (C.) species, analyze its impact on gene expression levels within C. albicans biofilms, and investigate the molecular interactions through molecular docking. The antifungal efficacy of artemisinin on a variety [...] Read more.

This study aimed to assess the antifungal and antibiofilm efficacy of artemisinin against Candida (C.) species, analyze its impact on gene expression levels within C. albicans biofilms, and investigate the molecular interactions through molecular docking. The antifungal efficacy of artemisinin on a variety of Candida species, including fluconazole-resistant and -susceptible species, was evaluated by the microdilution method. The effect of artemisinin on C. albicans biofilm formation was investigated by MTT and FESEM. The mRNA expression of the genes related to biofilm was analyzed by qRT-PCR. In addition, molecular docking analysis was used to understand the interaction between artemisinin and C. albicans at the molecular level with RAS1-cAMP-EFG1 and EFG1-regulated genes. Artemisinin showed higher sensitivity against non-albicans Candida strains. Furthermore, artemisinin was strongly inhibitory against C. albicans biofilms at 640 µg/mL. Artemisinin downregulated adhesion-related genes ALS3, HWP1, and ECE1, hyphal development genes UME6 and HGC1, and hyphal CAMP-dependent protein kinase regulators CYR1, RAS1, and EFG1. Furthermore, molecular docking analysis revealed that artemisinin and EFG1 had the highest affinity, followed by UME6. FESEM analysis showed that the fluconazole- and artemisinin-treated groups exhibited a reduced hyphal network, unusual surface bulges, and the formation of pores on the cell surfaces. Our study suggests that artemisinin may have antifungal potential and showed a remarkable antibiofilm activity by significantly suppressing adhesion and hyphal development through interaction with key proteins involved in biofilm formation, such as EFG1. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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20 pages, 9595 KiB

Open AccessArticle

Antimicrobial Activity of Bacillus amyloliquefaciens BS4 against Gram-Negative Pathogenic Bacteria

by Ana Paula Palacios-Rodriguez, Abraham Espinoza-Culupú, Yerson Durán and Tito Sánchez-Rojas

Antibiotics 2024, 13(4), 304; https://doi.org/10.3390/antibiotics13040304 - 28 Mar 2024

Cited by 2 | Viewed by 3333

Abstract

Worldwide, bacterial resistance is one of the most severe public health problems. Currently, the failure of antibiotics to counteract superbugs highlights the need to search for new molecules with antimicrobial potential to combat them. The objective of this research was to evaluate the [...] Read more.

Worldwide, bacterial resistance is one of the most severe public health problems. Currently, the failure of antibiotics to counteract superbugs highlights the need to search for new molecules with antimicrobial potential to combat them. The objective of this research was to evaluate the antimicrobial activity of Bacillus amyloliquefaciens BS4 against Gram-negative bacteria. Thirty yeasts and thirty-two Bacillus isolates were tested following the agar well-diffusion method. Four Bacillus sp. strains (BS3, BS4, BS17, and BS21) showed antagonistic activity against E. coli ATCC 25922 using bacterial culture (BC) and the cell-free supernatant (CFS), where the BS4 strain stood out, showing inhibitory values of 20.50 ± 0.70 mm and 19.67 ± 0.58 mm for BC and CFS, respectively. The Bacillus sp. BS4 strain can produce antioxidant, non-hemolytic, and antimicrobial metabolites that exhibit activity against several microorganisms such as Salmonella enterica, Klebsiella pneumoniae, Shigella flexneri, Enterobacter aerogenes, Proteus vulgaris, Yersinia enterocolitica, Serratia marcescens, Aeromonas sp., Pseudomonas aeruginosa, Candida albicans, and Candida tropicalis. According to the characterization of the supernatant, the metabolites could be proteinaceous. The production of these metabolites is influenced by carbon and nitrogen sources. The most suitable medium to produce antimicrobial metabolites was TSB broth. The one-factor-at-a-time method was used to standardize parameters such as pH, agitation, temperature, carbon source, nitrogen source, and salts, resulting in the best conditions of pH 7, 150 rpm, 28 °C, starch (2.5 g/L), tryptone (20 g/L), and magnesium sulfate (0.2 g/L), respectively. Moreover, the co-culture was an excellent strategy to improve antimicrobial activity, achieving maximum antimicrobial activity with an inhibition zone of 21.85 ± 1.03 mm. These findings position the Bacillus amyloliquefaciens BS4 strain as a promising candidate for producing bioactive molecules with potential applications in human health. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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Review

Jump to: Research

19 pages, 731 KiB

Open AccessReview

Anacardiaceae Family: Effect of Isolated Compounds and Other Identified Phytochemicals Against Clinically Relevant Candida Species—A Short Review

by Rosane Nassar Meireles Guerra, Aluísio Silva Oliveira, Josivan Regis Farias, Danielle Cristine Gomes Franco, Pamela Gomes Santos, Nicolle Teixeira Barbosa, Simone Batista Muniz, Afonso Gomes Abreu and Flavia Raquel Fernandes Nascimento

Antibiotics 2025, 14(3), 308; https://doi.org/10.3390/antibiotics14030308 - 17 Mar 2025

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Abstract

Background: The increased rates of common fungal diseases are a constant challenge. Therefore, the search for plant-based compounds with antifungal activity, particularly ones against Candida species, is always relevant in the medical context. However, most of the studies have focused on screening the [...] Read more.

Background: The increased rates of common fungal diseases are a constant challenge. Therefore, the search for plant-based compounds with antifungal activity, particularly ones against Candida species, is always relevant in the medical context. However, most of the studies have focused on screening the antifungal activity of extracts rather than isolated compounds. Based on this, we aimed to analyze and organize a comprehensive overview of the antifungal and other biological activities of isolated compounds found in Anacardiaceae family vegetal species, covering mechanisms of action and potential therapeutic applications. Results: The extracts, essential oils, and compounds are frequently assayed for anti-Candida activity using the in vitro minimum inhibitory concentration (MIC), minimum fungicide concentration (MFC), and halo inhibition assays. Candida albicans, C. tropicalis, C. parapsilosis, C. glabrata, C. krusei, and C. guilliermondii were the most tested fungus species. Essential oils were the most used form (37% of the studies). The isolated compounds included shikimic acid, 2-hydroxy-1,8-cineole β-D-glucopyranoside, myricitrin, cardanol, estragole, trans-anethole, β-caryophyllene, myrcene, catechin-3-O-rhamnoside, β-sitosterol-3-O-glucoside, 24Z-isomasticadienolic acid, oleanolic acid, pistagremic acid, apigenin, sakuranetin, oleanolic aldehyde, and integriside. Conclusions: Our data indicate that the compounds isolated from Anacardiaceae species show promise for developing new therapeutic antifungal drugs, mainly if we consider their other biological activities, including anti-inflammatory, antioxidant, and apoptotic effects. In this context, they may be candidates for future treatments of fungal infections, especially in combination with conventional antifungals or when used in nanostructured formulations, which may result in a new avenue of using plant extracts and isolated compounds. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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21 pages, 1602 KiB

Open AccessReview

A Comprehensive Review on the Antibacterial, Antifungal, Antiviral, and Antiparasitic Potential of Silybin

by José Lima Pereira-Filho, Amanda Graziela Gonçalves Mendes, Carmem Duarte Lima Campos, Israel Viegas Moreira, Cinara Regina Aragão Vieira Monteiro, Suzany Hellen da Silva Soczek, Elizabeth Soares Fernandes, Rafael Cardoso Carvalho and Valério Monteiro-Neto

Antibiotics 2024, 13(11), 1091; https://doi.org/10.3390/antibiotics13111091 - 15 Nov 2024

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Abstract

Silybin, a flavonolignan extracted from the seeds of the plant species Silybum marianum (L.) Gaertn., has a variety of pharmacological activities, including antimicrobial activity against several microorganisms of clinical interest. This review analyzes the existing studies on silybin’s antimicrobial activity and possible mechanisms [...] Read more.

Silybin, a flavonolignan extracted from the seeds of the plant species Silybum marianum (L.) Gaertn., has a variety of pharmacological activities, including antimicrobial activity against several microorganisms of clinical interest. This review analyzes the existing studies on silybin’s antimicrobial activity and possible mechanisms of action. Silybin has been shown to inhibit the growth of Gram-positive and Gram-negative bacteria, as well as some fungi, viruses, and protozoa. In general, possible mechanisms of antimicrobial action include the inhibition of efflux pumps, prevention of biofilm formation, reduction of the expression of virulence factors, induction of apoptosis-like effects, and plasma membrane damage, as well as the inhibition of nucleic acid and protein synthesis. Silybin has been shown to have synergistic effects when combined with conventional antibiotics against both drug-sensitive and drug-resistant microorganisms. However, the low bioavailability observed for this flavonolignan has been a challenge to its clinical use. In this context, nanotechnology has been used to increase silybin’s bioavailability while enhancing its antimicrobial activity. Furthermore, certain structural modifications have been able to enhance its antimicrobial activity in comparison to that of the natural molecule. Overall, this review provides insights into the scientific understanding of the mechanism of action of silybin and its desired properties for the effective treatment of infections. Full article

(This article belongs to the Special Issue Antimicrobial and Anti-Infective Activity of Natural Products, 2nd Edition)

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