Antimicrobial Resistance and Antimicrobial Activity of Natural Products and Derivatives

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "Novel Antimicrobial Agents".

Deadline for manuscript submissions: closed (31 August 2024) | Viewed by 5866

Special Issue Editors


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Department of Medical Microbiology & Immunology (MMI), RAK College of Medical Sciences (RAKCOMS), RAK Medical & Health Sciences University (RAKMHSU), Ras Al Khaimah, United Arab Emirates
Interests: antimicrobial resistance; diagnostic microbiology; immunology and antimicrobial agents
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Guest Editor
Department of Medical Microbiology & Infectious Diseases, Erasmus University Medical Center Rotterdam (Erasmus MC), 3015 GD Rotterdam, The Netherlands
Interests: medical microbiology; antimicrobial resistance; susceptibility testing and serology

Special Issue Information

Dear Colleagues,

Antimicrobial resistance (AMR) refers to the capability of microorganisms to resist the effects of antimicrobials that were previously effective in treating infections caused by them. This resistance can occur naturally or be selected through genetic mutations or acquired by the transfer of resistance genes between microorganisms. The overuse and misuse of antibiotics and other antimicrobial drugs are the leading causes of AMR. When antibiotics are prescribed unnecessarily, or when patients do not complete their full course of antibiotics, the bacteria that caused the infection can develop resistance to the drug, making it ineffective in treating the same infection. AMR is a growing public health threat that can contribute to increased morbidity, mortality, and healthcare costs. It can also limit the effectiveness of medical procedures such as chemotherapy, surgery, and organ transplantation. Preventing and controlling AMR requires a coordinated effort from healthcare providers, patients, and policymakers, including the responsible use of antibiotics and the development of new antimicrobial drugs.

The use of natural products as antimicrobial agents has attracted renewed interest in recent years, especially with the emergence of drug-resistant bacteria. Natural products have the potential to act as antimicrobial agents through various mechanisms, including inhibition of cell wall synthesis, disruption of membrane integrity, inhibition of protein synthesis, inhibition of DNA synthesis, and interference with metabolic pathways. Some examples of natural products with antimicrobial activity include: Plant-derived compounds (such as alkaloids, flavonoids, terpenoids, and phenolics), Essential oils, Marine-derived compounds and Microbial-derived compounds.  Despite the antimicrobial potential of natural products, there are several challenges that need to be overcome. These include the difficulty in obtaining sufficient quantities of some natural products, the complexity of their chemical structures, and the lack of standardized methods for evaluating their efficacy and safety. In conclusion, natural products have the potential to act as effective antimicrobial agents, and further research is needed to explore their potential for use in clinical settings.

This Special Issue therefore encourages authors to provide the public with cutting-edge original scientific manuscripts and reviews on the following topics:

  1. Antimicrobial Resistance
  2. Antimicrobial Activity of Natural Products and Derivatives

Dr. Godfred A. Menezes
Dr. Wil Goessens
Guest Editors

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Published Papers (3 papers)

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Research

18 pages, 2664 KiB  
Article
Efficacy of Trichoderma spp. and Kosakonia sp. Both Independently and Combined with Fungicides against Botrytis cinerea on Strawberries
by Tom E. Schierling, Wolfgang Vogt, Ralf T. Voegele and Abbas El-Hasan
Antibiotics 2024, 13(9), 912; https://doi.org/10.3390/antibiotics13090912 - 23 Sep 2024
Viewed by 1199
Abstract
Background: The ascomycete Botrytis cinerea is a major pathogen of strawberry, often causing grey mold and significant yield losses. Its management has largely relied on chemical fungicides, which, while effective, can lead to resistant pathogens and harm to non-target organisms and pose health [...] Read more.
Background: The ascomycete Botrytis cinerea is a major pathogen of strawberry, often causing grey mold and significant yield losses. Its management has largely relied on chemical fungicides, which, while effective, can lead to resistant pathogens and harm to non-target organisms and pose health risks. Objectives: This study explored a strategy for minimizing chemical usage by combining biocontrol agents (BCAs) with half-strength fungicide input. Results: In vitro results of fungicide-amended culture plates indicated that the presence of 625 µg mL−1 Azoxystrobin exhibited no growth inhibition of T. atroviride T19 and T. harzianum T16 but increased conidial density of T16 by 90%. Copper (750 µg mL−1) did not suppress the growth of T. virens TVSC or T16 but rather promoted it by 9.5% and 6%, respectively. Additionally, copper increased T16 sporulation by 1.4-fold. Greenhouse trials demonstrated that combining T23 with half-strength Azoxystrobin was as effective as the full dosage in suppressing flower rot. Among the antagonists assessed, Kosakonia sp. exhibited the lowest incidence of fruit rot, whereas T23 resulted in a moderate incidence. Moreover, the combination of T16 or Kosakonia sp. with half-strength copper was almost as effective as the full dosage in reducing fruit rot. Conclusions: Our findings suggest integrating these BCAs in the sustainable management of grey mold in strawberries. Full article
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18 pages, 2208 KiB  
Article
Fighting Emerging Caspofungin-Resistant Candida Species: Mitigating Fks1-Mediated Resistance and Enhancing Caspofungin Efficacy by Chitosan
by Aya Tarek, Yasmine H. Tartor, Mohamed N. Hassan, Ioan Pet, Mirela Ahmadi and Adel Abdelkhalek
Antibiotics 2024, 13(7), 578; https://doi.org/10.3390/antibiotics13070578 - 22 Jun 2024
Cited by 1 | Viewed by 1595
Abstract
Invasive candidiasis poses a worldwide threat because of the rising prevalence of antifungal resistance, resulting in higher rates of morbidity and mortality. Additionally, Candida species, which are opportunistic infections, have significant medical and economic consequences for immunocompromised individuals. This study explores the antifungal [...] Read more.
Invasive candidiasis poses a worldwide threat because of the rising prevalence of antifungal resistance, resulting in higher rates of morbidity and mortality. Additionally, Candida species, which are opportunistic infections, have significant medical and economic consequences for immunocompromised individuals. This study explores the antifungal potential of chitosan to mitigate caspofungin resistance in caspofungin-resistant Candida albicans, C. krusei, and C. tropicalis isolates originating from human and animal sources using agar well diffusion, broth microdilution tests, and transmission electron microscope (TEM) analysis of treated Candida cells. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) was performed to assess the expression of SAGA complex genes (GCN5 and ADA2) and the caspofungin resistance gene (FKS) in Candida species isolates after chitosan treatment. The highest resistance rate was observed to ketoconazole (80%) followed by clotrimazole (62.7%), fluconazole (60%), terbinafine (58%), itraconazole (57%), miconazole (54.2%), amphotericin B (51.4%), voriconazole (34.28%), and caspofungin (25.7%). Nine unique FKS mutations were detected, including S645P (n = 3 isolates), S645F, L644F, S645Y, L688M, E663G, and F641S (one isolate in each). The caspofungin minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values before chitosan treatment ranged from 2 to 8 µg/mL and 4 to 16 µg/mL, respectively. However, the MIC and MFC values were decreased after chitosan treatment (0.0625–1 µg/mL) and (0.125–2 µg/mL), respectively. Caspofungin MIC was significantly decreased (p = 0.0007) threefold following chitosan treatment compared with the MIC values before treatment. TEM analysis revealed that 0.5% chitosan disrupted the integrity of the cell surface, causing irregular morphologies and obvious aberrant changes in cell wall thickness in caspofungin-resistant and sensitive Candida isolates. The cell wall thickness of untreated isolates was 0.145 μm in caspofungin-resistant isolate and 0.125 μm in sensitive isolate, while it was significantly lower in chitosan-treated isolates, ranging from 0.05 to 0.08 μm when compared with the cell wall thickness of sensitive isolate (0.03 to 0.06 μm). Moreover, RT-qPCR demonstrated a significant (p < 0.05) decrease in the expression levels of histone acetyltransferase genes (GCN5 and ADA2) and FKS gene of caspofungin-resistant Candida species isolates treated with 0.5% chitosan when compared with before treatment (fold change values ranged from 0.001 to 0.0473 for GCN5, 1.028 to 4.856 for ADA2, and 2.713 to 12.38 for FKS gene). A comparison of the expression levels of cell wall-related genes (ADA2 and GCN5) between caspofungin-resistant and -sensitive isolates demonstrated a significant decrease following chitosan treatment (p < 0.001). The antifungal potential of chitosan enhances the efficacy of caspofungin against various caspofungin-resistant Candida species isolates and prevents the development of further antifungal resistance. The results of this study contribute to the progress in repurposing caspofungin and inform a development strategy to enhance its efficacy, appropriate antifungal activity against Candida species, and mitigate resistance. Consequently, chitosan could be used in combination with caspofungin for the treatment of candidiasis. Full article
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19 pages, 3394 KiB  
Article
Restraining Staphylococcus aureus Virulence Factors and Quorum Sensing through Lactic Acid Bacteria Supernatant Extracts
by Myriam Anabel Díaz, Esteban Gabriel Vega-Hissi, María Amparo Blázquez, María Rosa Alberto and Mario Eduardo Arena
Antibiotics 2024, 13(4), 297; https://doi.org/10.3390/antibiotics13040297 - 25 Mar 2024
Cited by 1 | Viewed by 2194
Abstract
The escalating prevalence of antibiotic-resistant bacteria poses a grave threat to human health, necessitating the exploration of novel alternatives to conventional antibiotics. This study investigated the impact of extracts derived from the supernatant of four lactic acid bacteria strains on factors contributing to [...] Read more.
The escalating prevalence of antibiotic-resistant bacteria poses a grave threat to human health, necessitating the exploration of novel alternatives to conventional antibiotics. This study investigated the impact of extracts derived from the supernatant of four lactic acid bacteria strains on factors contributing to the pathogenicity of three Staphylococcus aureus strains. The study evaluated the influence of lactic acid bacteria supernatant extracts on the growth, biofilm biomass formation, biofilm metabolic activity, and biofilm integrity of the S. aureus strains. Additionally, the impact on virulence factors (hemolysin and coagulase) was examined. Gas chromatography coupled with mass spectrometry was used to identify the bioactive compounds in the extracts, while molecular docking analyses explored potential interactions. Predominantly, the extracts contain eight 2,5-diketopiperazines, which are cyclic forms of peptides. The extracts demonstrated inhibitory effects on biofilm formation, the ability to disrupt mature biofilms, and reduce the biofilm cell metabolic activity of the S. aureus strains. Furthermore, they exhibited the ability to inhibit α-hemolysin production and reduce coagulase activity. An in silico docking analysis reveals promising interactions between 2,5-diketopiperazines and key proteins (SarA and AgrA) in S. aureus, confirming their antivirulence and antibiofilm activities. These findings suggest that 2,5-diketopiperazines could serve as a promising lead compound in the fight against antibiotic-resistant S. aureus. Full article
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