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Antibiotics
Special Issues
Microbial Biofilms, Antimicrobials, and Virulence Determinants
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Microbial Biofilms, Antimicrobials, and Virulence Determinants

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "Antibiofilm Strategies".

Deadline for manuscript submissions: closed (31 January 2024) | Viewed by 9798

Special Issue Editor

Dr. Luisa Jordao

E-Mail Website
Guest Editor
Instituto Nacional de Saúde Doutor Ricardo Jorge, Departamento de Saúde Ambiental, Unidade de Investigação e Desenvolvimento, Avenida Padre Cruz, 1649-016 Lisboa, Portugal
Interests: biofilms; environmental microorganisms; mycobacteria; infection; microscopy
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Biofilm formation is a successful survival strategy for microorganisms found in different environments. These structures formed by multiple microorganism species together with the secreted matrix could represent a challenge in case of human infections being a challenge in terms of diagnostic and treatment due to increased resistance to antimicrobial agents.

This issue will explore but is not restricted to the following topics:

  • Antimicrobial resistance mechanisms in biofilms;
  • Reports of confirmed biofilm-related infection cases;
  • Identification of virulence factors related to biofilms;
  • New methods to determine biofilms’ susceptibility to antimicrobial drugs and disinfectants;
  • Diagnostics of biofilm-related infections;
  • Biofilm prevention;
  • New anti-biofilm agents including drugs, disinfectants, modified surfaces;
  • Quorum sensing inhibitors;
  • Polymicrobial biofilms.

The proposed issue fits with the following topics of the journal: advances in research on new and current antibiotics and related bioactive medicinal agents; biochemical and genetics studies on microorganisms for improved antibiotics; new methods for assaying and evaluating antibiotics; natural antibiotics; qualitative and quantitative research exploring the determinants of antimicrobial use and resistance.

Dr. Luisa Jordao
Guest Editor

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 submissions that pass pre-check are 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 2900 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.

Keywords

  • biofilms
  • polymicrobial biofilms
  • antimicrobial resistance (AMR)
  • extracellular polymeric matrix
  • quorum sensing
  • virulence factors
  • biofilm control
  • biofilm prevention
  • new methodologies
  • antimicrobials

Published Papers (4 papers)

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Research

17 pages, 2679 KiB  
Article
Antibacterial and Antibiofilm Activity of Endophytic Alternaria sp. Isolated from Eremophila longifolia
by Daniel J. Caruso, Enzo A. Palombo, Simon E. Moulton, Peter J. Duggan and Bita Zaferanloo
Antibiotics 2023, 12(9), 1459; https://doi.org/10.3390/antibiotics12091459 - 19 Sep 2023
Cited by 1 | Viewed by 1311
Abstract
The threat to public health resulting from the emergence of antimicrobial resistance (AMR) is ever rising. One of the major bacterial pathogens at the forefront of this problem is methicillin-resistant Staphylococcus aureus, or MRSA, for which there is a great need to [...] Read more.
The threat to public health resulting from the emergence of antimicrobial resistance (AMR) is ever rising. One of the major bacterial pathogens at the forefront of this problem is methicillin-resistant Staphylococcus aureus, or MRSA, for which there is a great need to find alternative treatments. One of the most promising alternatives is endophytic fungi, which were shown to produce a vast array of bioactive compounds, including many novel antibacterial compounds. In this study, two endophytic Alternaria sp., EL 24 and EL 35, were identified from the leaves of Eremophila longifolia. Ethyl acetate (EtOAc) extracts of their culture filtrates were found to inhibit both methicillin-sensitive S. aureus ATCC 25923 and MRSA strains M173525 and M180920. The activity of each extract was shown to be greatly affected by the growth medium, with considerable reductions in minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) observed when tested in tryptic soy broth with glucose (TSBG) compared with Mueller–Hinton broth (MHB). Both extracts displayed significant (p ≤ 0.05) antibiofilm activity against all three S. aureus strains, the greatest of which was that of EL 35, which reduced biofilm formation by M180920 by 72%, while that of EL 24 resulted in a 57% reduction against ATCC 25923. Both extracts also disrupted established biofilms, of which the most effective was EL 35, which reduced the M180920 biofilm by 64%, while EL 24 also performed best against M180920, reducing biofilm by 54%. Gas chromatography–mass spectrometry (GC-MS) analysis of the EL 24 EtOAc extract revealed five known compounds. This study highlights the promise of endophytic fungi from Australian plants as a potential source of substances effective against important bacterial pathogens. Further understanding of the responsible compounds and their mechanisms could lead to the development of treatments effective against MRSA, as well as novel biofilm-resistant biomedical materials, contributing towards reducing the burden of AMR. Full article
(This article belongs to the Special Issue Microbial Biofilms, Antimicrobials, and Virulence Determinants)
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18 pages, 2023 KiB  
Article
Effect of Quorum Sensing Molecule Farnesol on Mixed Biofilms of Candida albicans and Staphylococcus aureus
by Barbora Gaálová-Radochová, Samuel Kendra, Luisa Jordao, Laura Kursawe, Judith Kikhney, Annette Moter and Helena Bujdáková
Antibiotics 2023, 12(3), 441; https://doi.org/10.3390/antibiotics12030441 - 23 Feb 2023
Cited by 3 | Viewed by 1824
Abstract
The natural bioactive molecule farnesol (FAR) is widely studied mainly for its antibiofilm and antimicrobial properties. In addition, it increases the effectiveness of some antimicrobial substances, which makes it interesting for the development of combined therapy. In the present work, the effect of [...] Read more.
The natural bioactive molecule farnesol (FAR) is widely studied mainly for its antibiofilm and antimicrobial properties. In addition, it increases the effectiveness of some antimicrobial substances, which makes it interesting for the development of combined therapy. In the present work, the effect of FAR either alone or in combination with oxacillin (OXA) on mixed biofilms formed by clinically relevant pathogens, Candida albicans and Staphylococcus aureus, was studied. S. aureus isolates used for biofilm formation originated from blood cultures and central venous catheters (CVC) were characterized in terms of antimicrobial resistance. The minimal biofilm inhibitory concentration (MBIC50) for FAR of 48 h mixed biofilms formed by the C. albicans and methicillin-sensitive S. aureus (MSSA) was determined to be 125 μM, and for the mixed biofilms with methicillin-resistant S. aureus (MRSA) was determined to be 250 μM. Treatment of mixed biofilms with OXA (2 mg/mL) showed ≤4% inhibition; however, the combination of OXA (2 mg/mL) and FAR (300 μM) resulted in 80% inhibition of biofilms. In addition, planktonic cells of S. aureus exhibited an increased susceptibility to OXA, cefoxitin and kanamycin in the presence of FAR (150 and 300 μM). Scanning electron microscopy (SEM) micrographs confirmed patchy biofilm and lack of candidal hyphae in the samples treated with FAR and FAR/OXA in comparison to control and mixed biofilms treated only with OXA. Intriguingly, in a pilot experiment using fluorescence in situ hybridization (FISH), considerable differences in activity (as indicated by ribosome content) of staphylococcal cells were detected. While the activity rate of the staphylococci in mixed biofilms treated with FAR was high, no FISH-positive signal for staphylococcal cells was found in the biofilm treated with FAR/OXA. Full article
(This article belongs to the Special Issue Microbial Biofilms, Antimicrobials, and Virulence Determinants)
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18 pages, 6753 KiB  
Article
Antimicrobial Resistance and Biofilms Underlying Catheter-Related Bloodstream Coinfection by Enterobacter cloacae Complex and Candida parapsilosis
by Matúš Štefánek, Sigurd Wenner, Vítor Borges, Miguel Pinto, João Paulo Gomes, João Rodrigues, Isabel Faria, Maria Ana Pessanha, Filomena Martins, Raquel Sabino, Cristina Veríssimo, Isabel D. Nogueira, Patrícia Almeida Carvalho, Helena Bujdáková and Luisa Jordao
Antibiotics 2022, 11(9), 1245; https://doi.org/10.3390/antibiotics11091245 - 14 Sep 2022
Cited by 6 | Viewed by 2615
Abstract
Biofilm-associated infections are a public health concern especially in the context of healthcare-associated infections such as catheter-related bloodstream infections (CRBSIs). We evaluated the biofilm formation and antimicrobials resistance (AMR) of Enterobacter cloacae complex and Candida parapsilosis co-isolated from a CRBSI patient. Antimicrobial susceptibility [...] Read more.
Biofilm-associated infections are a public health concern especially in the context of healthcare-associated infections such as catheter-related bloodstream infections (CRBSIs). We evaluated the biofilm formation and antimicrobials resistance (AMR) of Enterobacter cloacae complex and Candida parapsilosis co-isolated from a CRBSI patient. Antimicrobial susceptibility of central venous catheters (CVCs) and hemoculture (HC) isolates was evaluated, including whole genome sequencing (WGS) resistome analysis and evaluation of gene expression to obtain insight into their AMR determinants. Crystal violet assay was used to assess dual biofilm biomass and microscopy was used to elucidate a microorganism’s distribution within biofilms assembled on different materials. Bacteria were multidrug-resistant including resistance to colistin and beta-lactams, likely linked to the mcr-9-like phosphoethanolamine transferase and to an ACT family cephalosporin-hydrolyzing class C beta-lactamase, respectively. The R398I and Y132F mutations in the ERG11 gene and its differential expression might account for C. parapsilosis resistance to fluconazole. The phenotype of dual biofilms assembled on glass, polystyrene and polyurethane depends on the material and how biofilms were initiated by one or both pathogens. Biofilms assembled on polyurethane were denser and richer in the extracellular polymeric matrix, and microorganisms were differently distributed on the inner/outer surface of the CVC. Full article
(This article belongs to the Special Issue Microbial Biofilms, Antimicrobials, and Virulence Determinants)
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9 pages, 1983 KiB  
Article
Essential Oils as a Good Weapon against Drug-Resistant Candida auris
by Liliana Fernandes, Rita Ribeiro, Raquel Costa, Mariana Henriques and M. Elisa Rodrigues
Antibiotics 2022, 11(7), 977; https://doi.org/10.3390/antibiotics11070977 - 20 Jul 2022
Cited by 11 | Viewed by 3388
Abstract
Candida auris is a recently found Candida species, mainly associated with nosocomial outbreaks in intensive care hospital settings, and unlike other Candida species, it can be transmitted through person-to-person or by contact with surfaces. C. auris is described as resistant to first-line antifungals [...] Read more.
Candida auris is a recently found Candida species, mainly associated with nosocomial outbreaks in intensive care hospital settings, and unlike other Candida species, it can be transmitted through person-to-person or by contact with surfaces. C. auris is described as resistant to first-line antifungals and, consequently, associated with high mortality. Nowadays, essential oils (EOs) are known to be effective against fungal and bacterial infections. This work aimed to evaluate the effect of four EOs (tea tree, niaouli, white thyme and cajeput) against C. auris. The EO’s effect on C. auris planktonic growth was evaluated by the minimum inhibitory concentration determination and by the agar disc diffusion method. Then, the same effect was evaluated on biofilm by colony-forming units’ enumeration. The results showed that EOs were able to inhibit the C. auris planktonic growth, with an MIC50 between 0.78 and 1.56% and halos of 20–21 mm for white thyme and tea tree and 13–14 mm for cajeput and niaouli. In addition, the EOs were also able to completely inhibit biofilm formation. Moreover, white thyme and cajeput completely eradicate pre-formed biofilms, while tea tree and niaouli significantly reduce it. Thus, this work demonstrates that EOs are a possible therapeutic alternative and a future perspective for the hard fight against C. auris. Full article
(This article belongs to the Special Issue Microbial Biofilms, Antimicrobials, and Virulence Determinants)
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