Special Issue "Natural Antimicrobials and Alternatives to Antimicrobials"

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

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Prof. Dr. David Martin
E-Mail Website
Guest Editor
Institute of Integrative Medicine, University of Witten/Herdecke , Herdecke, Germany
Interests: Pediatrics, pediatric oncology, integrative medicine, fever
Dr. Merlin Willcox
E-Mail Website
Guest Editor
School of Primary Care, Population Sciences and Medical Education, University of Southampton
Interests: Herbal medicine, primary care, common infections, antibiotic stewardship, global health
Dr. Xiao-Yang (Mio) Hu
E-Mail Website
Guest Editor
School of Primary Care, Population Sciences and Medical Education, University of Southampton
Interests: Integrative medicine, traditional Chinese medicine, antibiotic stewardship
Prof. Dr. Michael Moore
E-Mail Website
Guest Editor
School of Primary Care, Population Sciences and Medical Education, University of Southampton
Interests: Primary care, antibiotic stewardship, acute infections

Special Issue Information

Dear Colleagues,

Following on from the two Special Issues “Natural Compounds as Antimicrobial Agents”, we would like to produce a clinically oriented Special Issue on “Natural Alternatives to Antimicrobials”.

The focus is on natural and complementary medicine in humans as a tool for antibiotic stewardship.

Thus, this Special Issue will cover, but is not limited to, the following topics:

  • Herbal preparations
  • Complementary and alternative treatments for fever
  • New natural antimicrobial compounds
  • Antimicrobial effects
  • Clinical applications
  • Antifungal properties
  • Antiviral properties
  • Antibacterial mechanisms
  • Antifungal mechanisms
  • New formulations
  • Anthroposophic Medicine,
  • Ayurvedic Medicine
  • Traditional Chinese Medicine
  • Activity as disinfectants
  • Combination with other antimicrobials
  • Global microbiome changes
  • Acupuncture and moxibustion
  • Probiotics

Prof. Dr. David Martin
Dr. Merlin Willcox
Dr. Xiao-Yang (Mio) Hu
Prof. Dr. Mike Moore
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Antibiotics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (6 papers)

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Research

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Open AccessArticle
Antimicrobial Effect and the Mechanism of Diallyl Trisulfide against Campylobacter jejuni
Antibiotics 2021, 10(3), 246; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10030246 - 02 Mar 2021
Viewed by 276
Abstract
Campylobacter jejuni is an important foodborne pathogen causing campylobacteriosis. It can infect humans through the consumption of contaminated chicken products or via the direct handling of animals. Diallyl trisulfide (DATS) is a trisulfide compound from garlic extracts that has a potential antimicrobial effect [...] Read more.
Campylobacter jejuni is an important foodborne pathogen causing campylobacteriosis. It can infect humans through the consumption of contaminated chicken products or via the direct handling of animals. Diallyl trisulfide (DATS) is a trisulfide compound from garlic extracts that has a potential antimicrobial effect on foodborne pathogens. This study investigated the antimicrobial activity of DATS on C. jejuni by evaluating the minimal inhibitory concentrations (MICs) of C. jejuni 81-168, and fourteen C. jejuni isolates from chicken carcasses. Thirteen of 14 C. jejuni isolates and 81-176 had MICs ≤ 32 μg/mL, while one isolate had MIC of 64 μg/mL. Scanning electron microscopy (SEM) analysis showed the disruption and shrink of C. jejuni bacterial cell membrane after the DATS treatment. A time-killing analysis further showed that DATS had a dose-dependent in vitro antimicrobial effect on C. jejuni during the 24 h treatment period. In addition, DATS also showed an antimicrobial effect in chicken through the decrease of C. jejuni colony count by 1.5 log CFU/g (cloacal sample) during the seven-day DATS treatment period. The transcriptional analysis of C. jejuni with 16 μg/mL (0.5× MIC) showed 210 differentially expression genes (DEGs), which were mainly related to the metabolism, bacterial membrane transporter system and the secretion system. Fourteen ABC transporter-related genes responsible for bacterial cell homeostasis and oxidative stress were downregulated, indicating that DATS could decrease the bacterial ability to against environmental stress. We further constructed five ABC transporter deletion mutants according to the RNA-seq analysis, and all five mutants proved less tolerant to the DATS treatment compared to the wild type by MIC test. This study elucidated the antimicrobial activity of DATS on C. jejuni and suggested that DATS could be used as a potential antimicrobial compound in the feed and food industry. Full article
(This article belongs to the Special Issue Natural Antimicrobials and Alternatives to Antimicrobials)
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Open AccessArticle
The P.E.A.N.U.T. Method: Update on an Integrative System Approach for the Treatment of Chronic Otitis Media with Effusion and Adenoid Hypertrophy in Children
Antibiotics 2021, 10(2), 134; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10020134 - 30 Jan 2021
Viewed by 605
Abstract
Background and objectives: Based on our previous single-center study on optimization of treatment of chronic otitis media with effusion (COME) and adenoid hypertrophy (AH) in children using a noninvasive system approach to lower the necessity of antibiotics, analgesic use, and surgical interventions, we [...] Read more.
Background and objectives: Based on our previous single-center study on optimization of treatment of chronic otitis media with effusion (COME) and adenoid hypertrophy (AH) in children using a noninvasive system approach to lower the necessity of antibiotics, analgesic use, and surgical interventions, we proceeded to perform a multicenter investigation in an outpatient setting. The purpose of the previous prospective study in 2013–2015 was to compare outcomes in the treatment of COME and AH using the noninvasive multimodal integrative method (IM) versus conventional treatment practice (COM). Materials and Methods: In this paper, we retrospectively analyze the data of patients treated with the integrative method between 2017 and 2020 in a multicenter setting and compared the outcomes with data from 2013–2015 in order to evaluate generalizability. In both periods, all eligible and willing participants were included and treated with the IM protocol under real-life conditions. The treatment involved pneumatization exercises, education, an antiallergic diet, nasal hygiene, useful constitutional therapy, and thermal interventions (P.E.A.N.U.T.). A total of 48 versus 28 patients, aged 1–8, were assessed, presenting with COME and AH, with moderate to severe hearing impairment at entry. Results: The significant improvement found in both audiometric measures (intact hearing) and tympanometric measures (normal A-type curve) was similar in both datasets with respect to conventional treatment. The new data confirms that the P.E.A.N.U.T. method results in a significant reduction of antibiotics, analgesic use, and surgical interventions. Conclusion: In this multicenter trial, we confirm the effectiveness of the noninvasive system approach for the treatment of COME in lowering the need for antibiotics and analgesic use and elective surgery. This could be especially important with respect to a generally observed increase in antibiotic resistance. The method is easy to perform in different clinical settings and is effective, safe, and well-tolerated. Full article
(This article belongs to the Special Issue Natural Antimicrobials and Alternatives to Antimicrobials)
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Open AccessArticle
Inhibition of Biofilm Formation by the Synergistic Action of EGCG-S and Antibiotics
Antibiotics 2021, 10(2), 102; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10020102 - 21 Jan 2021
Viewed by 577
Abstract
Biofilm, a stress-induced physiological state, is an established means of antimicrobial tolerance. A perpetual increase in multidrug resistant (MDR) infections associated with high mortality and morbidity have been observed in healthcare settings. Multiple studies have indicated that the use of natural products can [...] Read more.
Biofilm, a stress-induced physiological state, is an established means of antimicrobial tolerance. A perpetual increase in multidrug resistant (MDR) infections associated with high mortality and morbidity have been observed in healthcare settings. Multiple studies have indicated that the use of natural products can prevent bacterial growth. Recent studies in the field have identified that epigallocatechin gallate (EGCG), a green tea polyphenol, could disrupt bacterial biofilms. A modified lipid-soluble EGCG, epigallocatechin-3-gallate-stearate (EGCG-S), has enhanced the beneficial properties of green tea. This study focuses on utilizing EGCG-S as a novel synergistic agent with antibiotics to prevent or control biofilm. Different formulations of EGCG-S and selected antibiotics were used to study their combinatorial effects on biofilms produced by five potential pathogenic bacteria, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcusepidermidis, and Mycobacterium smegmatis. The crystal violet (CV) assay and the sensitive fluorescence-based resazurin biofilm viability assay were used to assess the biofilm production. Our results identified optimal formulation for each bacterium, effectively inhibiting biofilm formation to an extent of 95–99%. Colony-forming unit (CFU) and cell viability analyses showed a decrease of viable bacteria. These results depict the potential of EGCG-S as a synergistic agent with antibiotics and as an anti-biofilm agent. Full article
(This article belongs to the Special Issue Natural Antimicrobials and Alternatives to Antimicrobials)
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Open AccessArticle
Thymol Nanoemulsion: A New Therapeutic Option for Extensively Drug Resistant Foodborne Pathogens
Antibiotics 2021, 10(1), 25; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10010025 - 30 Dec 2020
Cited by 2 | Viewed by 779
Abstract
Foodborne pathogens have been associated with severe and complicated diseases. Therefore, these types of infections are a concern for public health officials and food and dairy industries. Regarding the wide-spread multidrug resistant (MDR) and extensively drug resistant (XDR) foodborne pathogens such as Salmonella [...] Read more.
Foodborne pathogens have been associated with severe and complicated diseases. Therefore, these types of infections are a concern for public health officials and food and dairy industries. Regarding the wide-spread multidrug resistant (MDR) and extensively drug resistant (XDR) foodborne pathogens such as Salmonella Enteritidis (S. Enteritidis), new and alternative therapeutic approaches are urgently needed. Therefore, we investigated the antimicrobial, anti-virulence, and immunostimulant activities of a stable formulation of thymol as thymol nanoemulsion in an in vivo approach. Notably, treatment with 2.25% thymol nanoemulsion led to a pronounced improvement in the body weight gain and feed conversion ratio in addition to decreases in the severity of clinical findings and mortality percentages of challenged chickens with XDR S. Enteritidis confirming its pronounced antimicrobial activities. Moreover, thymol nanoemulsion, at this dose, had protective effects through up-regulation of the protective cytokines and down-regulation of XDR S. Enteritidis sopB virulence gene and interleukins (IL)-4 and IL-10 cytokines as those hinder the host defenses. Furthermore, it enhanced the growth of gut Bifidobacteria species, which increases the strength of the immune system. For that, we suggested the therapeutic use of thymol nanoemulsion against resistant foodborne pathogens. Finally, we recommended the use of 2.25% thymol nanoemulsion as a feed additive for immunocompromised individuals as well as in the veterinary fields. Full article
(This article belongs to the Special Issue Natural Antimicrobials and Alternatives to Antimicrobials)
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Open AccessArticle
Antimicrobial Effects of Essential Oils on Oral Microbiota Biofilms: The Toothbrush In Vitro Model
Antibiotics 2021, 10(1), 21; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10010021 - 29 Dec 2020
Viewed by 677
Abstract
The present investigation intended to evaluate the bacteriostatic and bactericidal abilities of clove, oregano and thyme essential oils against oral bacteria in planktonic and biofilm states. Furthermore, aiming to mimic everyday conditions, a toothbrush in vitro model was developed. Determination of the minimum [...] Read more.
The present investigation intended to evaluate the bacteriostatic and bactericidal abilities of clove, oregano and thyme essential oils against oral bacteria in planktonic and biofilm states. Furthermore, aiming to mimic everyday conditions, a toothbrush in vitro model was developed. Determination of the minimum inhibitory concentration, minimum bactericidal concentration, minimum biofilm inhibitory concentration and minimum biofilm eradication concentration were achieved using the microdilution procedure. To simulate the toothbrush environment, nylon fibers were inoculated with oral bacteria, which, after incubation to allow biofilm development, were submitted to contact with the essential oils under study. Thyme and oregano essential oils revealed promising antimicrobial effects, both in growth inhibition and the destruction of cells in planktonic and biofilm states, while clove essential oil showed a weaker potential. Regarding the toothbrush in vitro model, observation of the nylon fibers under a magnifying glass proved the essential oil anti-biofilm properties. Considering the effects observed using the in vitro toothbrush model, a realistic approximation to oral biofilm establishment in an everyday use object, a putative application of essential oils as toothbrush sanitizers to help prevent the establishment of bacterial biofilm can be verified. Full article
(This article belongs to the Special Issue Natural Antimicrobials and Alternatives to Antimicrobials)
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Review

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Open AccessReview
Staphylococcal Biofilms: Challenges and Novel Therapeutic Perspectives
Antibiotics 2021, 10(2), 131; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10020131 - 29 Jan 2021
Cited by 1 | Viewed by 869
Abstract
Staphylococci, like Staphylococcus aureus and S. epidermidis, are common colonizers of the human microbiota. While being harmless in many cases, many virulence factors result in them being opportunistic pathogens and one of the major causes of hospital-acquired infections worldwide. One of these [...] Read more.
Staphylococci, like Staphylococcus aureus and S. epidermidis, are common colonizers of the human microbiota. While being harmless in many cases, many virulence factors result in them being opportunistic pathogens and one of the major causes of hospital-acquired infections worldwide. One of these virulence factors is the ability to form biofilms—three-dimensional communities of microorganisms embedded in an extracellular polymeric matrix (EPS). The EPS is composed of polysaccharides, proteins and extracellular DNA, and is finely regulated in response to environmental conditions. This structured environment protects the embedded bacteria from the human immune system and decreases their susceptibility to antimicrobials, making infections caused by staphylococci particularly difficult to treat. With the rise of antibiotic-resistant staphylococci, together with difficulty in removing biofilms, there is a great need for new treatment strategies. The purpose of this review is to provide an overview of our current knowledge of the stages of biofilm development and what difficulties may arise when trying to eradicate staphylococcal biofilms. Furthermore, we look into promising targets and therapeutic methods, including bacteriocins and phage-derived antibiofilm approaches. Full article
(This article belongs to the Special Issue Natural Antimicrobials and Alternatives to Antimicrobials)
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