Special Issue "New Insights on Biofilm Antimicrobial Strategies, 2nd Volume"

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

Deadline for manuscript submissions: 31 January 2022.

Special Issue Editors

Dr. Luís Melo
E-Mail Website
Guest Editor
Laboratory of Research in Biofilms Rosário Oliveira, Centre of Biological Engineering, University of Minho, Braga, Portugal
Interests: bacteriophage; phage-host interactions; biofilms; endolysins; phage therapy; phage genomics and evolution
Special Issues, Collections and Topics in MDPI journals
Dr. Andreia S. Azevedo
E-Mail Website
Guest Editor
Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Porto, Portugal
Interests: multispecies biofilms;; antibiotic agents; nucleic acid mimics; Fluorescence in situ hybridization; human microbiota

Special Issue Information

Dear Colleagues,

The first volume of the Special Issue “New Insights on Biofilm Antimicrobial Strategies” was published in the past year. It is a successful issue with 15 published papers and has encouraged us to open a second volume with the same topic.

As a continuation of the Special Issue published in 2020, this second volume will deal with different strategies to prevent biofilm formation or control development. The issue welcomes various submission types, such as original research papers, short communications, reviews, case reports, and perspectives.

Potential topics for this Special Issue include but are not limited to different antifouling strategies:

  • Phages or phage-derived enzymes
  • Use of physical approaches (photoporation; sonoporation)
  • Development of antimicrobial peptides or nucleic acid mimics
  • Use of natural products
  • Modification of surfaces to prevent biofilm formation
  • Combinations of antimicrobial agents with a synergistic effect

Dr. Luís Melo
Dr. Andreia Azevedo
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.

Keywords

  • biofilm prevention
  • biofilm control
  • surface modifications
  • new generation antimicrobial compounds
  • synergistic approaches

Published Papers (8 papers)

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Research

Article
Antifungal and Anti-Biofilm Effects of Caffeic Acid Phenethyl Ester on Different Candida Species
Antibiotics 2021, 10(11), 1359; https://doi.org/10.3390/antibiotics10111359 - 07 Nov 2021
Viewed by 430
Abstract
This study investigated the effect of CAPE on planktonic growth, biofilm-forming abilities, mature biofilms, and cell death of C. albicans, C. tropicalis, C. glabrata, and C. parapsilosis strains. Our results showed a strain- and dose-dependent effect of CAPE on Candida [...] Read more.
This study investigated the effect of CAPE on planktonic growth, biofilm-forming abilities, mature biofilms, and cell death of C. albicans, C. tropicalis, C. glabrata, and C. parapsilosis strains. Our results showed a strain- and dose-dependent effect of CAPE on Candida, and the MIC values were between 12.5 and 100 µg/mL. Similarly, the MBIC values of CAPE ranging between 50 and 100 µg/mL highlighted the inhibition of the biofilm-forming abilities in a dose-dependent manner, as well. However, CAPE showed a weak to moderate biofilm eradication ability (19-49%) on different Candida strains mature biofilms. Both caspase-dependent and caspase-independent apoptosis after CAPE treatment were observed in certain tested Candida strains. Our study has displayed typical apoptotic hallmarks of CAPE-induced chromatin margination, nuclear blebs, nuclear condensation, plasma membrane detachment, enlarged lysosomes, cytoplasm fragmentation, cell wall distortion, whole-cell shrinkage, and necrosis. In conclusion, CAPE has a concentration and strain-dependent inhibitory activity on viability, biofilm formation ability, and cell death response in the different Candida species. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Article
Antibacterial Property of Cellulose Acetate Composite Materials Reinforced with Aluminum Nitride
Antibiotics 2021, 10(11), 1292; https://doi.org/10.3390/antibiotics10111292 - 22 Oct 2021
Viewed by 382
Abstract
Cellulose acetate (CA) is a synthetic compound that is derived from the acetylation of cellulose. CA is well known as it has been used for many commercial products such as textiles, plastic films, and cigarette filters. In this research, antibacterial CA composites were [...] Read more.
Cellulose acetate (CA) is a synthetic compound that is derived from the acetylation of cellulose. CA is well known as it has been used for many commercial products such as textiles, plastic films, and cigarette filters. In this research, antibacterial CA composites were produced by addition of aluminum nitride (AlN) at different weight percentage, from 0 wt. % to 20 wt. %. The surface characterization was performed using laser microscope, Raman and FTIR spectroscopy. The mechanical and thermal properties of the composite were analyzed. Although the mechanical strength tended to decrease as the concentration of AlN increased and needed to be optimized, the melting temperature (Tm) and glass transition temperature (Tg) showed a shift toward higher values as the AlN concentration increased leading to an improvement in thermal properties. AlN additions in weight percentages >10 wt. % led to appreciable antibacterial properties against S. epidermidis and E. coli bacteria. Antibacterial CA/AlN composites with higher thermal stability have potential applications as alternative materials for plastic packaging in the food industry. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Article
Efficacy of Novel Bacteriophages against Escherichia coli Biofilms on Stainless Steel
Antibiotics 2021, 10(10), 1150; https://doi.org/10.3390/antibiotics10101150 - 24 Sep 2021
Viewed by 579
Abstract
Biofilm formation by E. coli is a serious threat to meat processing plants. Chemical disinfectants often fail to eliminate biofilms; thus, bacteriophages are a promising alternative to solve this problem, since they are widely distributed, environmentally friendly, and nontoxic to humans. In this [...] Read more.
Biofilm formation by E. coli is a serious threat to meat processing plants. Chemical disinfectants often fail to eliminate biofilms; thus, bacteriophages are a promising alternative to solve this problem, since they are widely distributed, environmentally friendly, and nontoxic to humans. In this study, the biofilm formation of 10 E. coli strains isolated from the meat industry and E. coli ATCC BAA-1430 and ATCC 11303 were evaluated. Three strains, isolated from the meat contact surfaces, showed adhesion ability and produced extracellular polymeric substances. Biofilms of these three strains were developed onto stainless steel (SS) surfaces and enumerated at 2, 12, 24, 48, and 120 h, and were visualized by scanning electron microscopy. Subsequently, three bacteriophages showing podovirus morphology were isolated from ground beef and poultry liver samples, which showed lytic activity against the abovementioned biofilm-forming strains. SS surfaces with biofilms of 2, 14, and 48 h maturity were treated with mixed and individual bacteriophages at 8 and 9 log10 PFU/mL for 1 h. The results showed reductions greater than 6 log10 CFU/cm2 as a result of exposing SS surfaces with biofilms of 24 h maturity to 9 log10 PFU/mL of bacteriophages; however, the E. coli and bacteriophage strains, phage concentration, and biofilm development stage had significant effects on biofilm reduction (p < 0.05). In conclusion, the isolated bacteriophages showed effectiveness at reducing biofilms of isolated E. coli; however, it is necessary to increase the libraries of phages with lytic activity against the strains isolated from production environments. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Article
Thermal Shock and Ciprofloxacin Act Orthogonally on Pseudomonas aeruginosa Biofilms
Antibiotics 2021, 10(8), 1017; https://doi.org/10.3390/antibiotics10081017 - 21 Aug 2021
Viewed by 570
Abstract
Bacterial biofilm infections are a major liability of medical implants, due to their resistance to both antibiotics and host immune response. Thermal shock can kill established biofilms, and some evidence suggests antibiotics may enhance this efficacy, despite having an insufficient effect themselves. The [...] Read more.
Bacterial biofilm infections are a major liability of medical implants, due to their resistance to both antibiotics and host immune response. Thermal shock can kill established biofilms, and some evidence suggests antibiotics may enhance this efficacy, despite having an insufficient effect themselves. The nature of this interaction is unclear, however, complicating efforts to integrate thermal shock into implant infection treatment. This study aimed to determine whether these treatments were truly synergistic or simply orthogonal (i.e., independent). Pseudomonas aeruginosa biofilms of different architectures and stationary-phase population density were subjected to various thermal shocks, antibiotic exposures, or combinations thereof, and examined either immediately after treatment or after subsequent reincubation. Population decreases from the combination treatment matched the product of the decreases of individual treatments, indicating their orthogonality. However, reincubation showed binary behavior, where biofilms with an immediate population decrease beyond a critical factor (~104) died off completely during reincubation, while biofilms with a smaller immediate decrease regrew. This critical factor was independent of the initial population density and the combination of treatments that achieved the immediate decrease. While antibiotics do not appear to enhance thermal shock directly, their contribution to achieving a critical population decrease for biofilm elimination can make the treatments appear strongly synergistic, strongly decreasing the intensity of thermal shock needed. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Article
Removal of Mixed-Species Biofilms Developed on Food Contact Surfaces with a Mixture of Enzymes and Chemical Agents
Antibiotics 2021, 10(8), 931; https://doi.org/10.3390/antibiotics10080931 - 30 Jul 2021
Viewed by 550
Abstract
Sanicip Bio Control (SBC) is a novel product developed in Mexico for biofilms’ removal. The aims of this study were to evaluate (i) the removal of mixed-species biofilms by enzymatic (protease and α-amylase, 180 MWU/g) and chemical treatments (30 mL/L SBC, and 200 [...] Read more.
Sanicip Bio Control (SBC) is a novel product developed in Mexico for biofilms’ removal. The aims of this study were to evaluate (i) the removal of mixed-species biofilms by enzymatic (protease and α-amylase, 180 MWU/g) and chemical treatments (30 mL/L SBC, and 200 mg/L peracetic acid, PAA) and (ii) their effectiveness against planktonic cells. Mixed-species biofilms were developed on stainless steel (SS) and polypropylene B (PP) in whole milk (WM), tryptic soy broth (TSB) with meat extract (TSB+ME), and TSB with chicken egg yolk (TSB+EY) to simulate the food processing environment. On SS, all biofilms were removed after treatments, except the enzymatic treatment that only reduced 1–2 log10 CFU/cm2, whereas on PP, the reductions ranged between 0.59 and 5.21 log10 CFU/cm2, being the biofilms developed in TSB+EY being resistant to the cleaning and disinfecting process. Higher reductions in microbial load on PP were reached using enzymes, SBC, and PAA. The employed planktonic cells were markedly more sensitive to PAA and SBC than were the sessile cells. In conclusion, biofilm removal from SS can be achieved with SBC, enzymes, or PAA. It is important to note that the biofilm removal was strongly affected by the food contact surfaces (FCSs) and surrounding media. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Article
Natural and Enantiopure Alkylglycerols as Antibiofilms Against Clinical Bacterial Isolates and Quorum Sensing Inhibitors of Chromobacterium violaceum ATCC 12472
Antibiotics 2021, 10(4), 430; https://doi.org/10.3390/antibiotics10040430 - 13 Apr 2021
Cited by 1 | Viewed by 682
Abstract
Resistance mechanisms occur in almost all clinical bacterial isolates and represent one of the most worrisome health problems worldwide. Bacteria can form biofilms and communicate through quorum sensing (QS), which allow them to develop resistance against conventional antibiotics. Thus, new therapeutic candidates are [...] Read more.
Resistance mechanisms occur in almost all clinical bacterial isolates and represent one of the most worrisome health problems worldwide. Bacteria can form biofilms and communicate through quorum sensing (QS), which allow them to develop resistance against conventional antibiotics. Thus, new therapeutic candidates are sought. We focus on alkylglycerols (AKGs) because of their recently discovered quorum sensing inhibition (QSI) ability and antibiofilm potential. Fifteen natural enantiopure AKGs were tested to determine their effect on the biofilm formation of other clinical bacterial isolates, two reference strains and their QSI was determined using Chromobacterium violaceum ATCC 12472. The highest biofilm inhibition rates (%) and minimum QS inhibitory concentration were determined by a microtiter plate assay and ciprofloxacin was used as the standard antibiotic. At subinhibitory concentrations, each AKG reduced biofilm formation in a concentration-dependent manner against seven bacterial isolates, with values up to 97.2%. Each AKG displayed QSI at different levels of ability without affecting the growth of C. violaceum. AKG (2S)-3-O-(cis-13’-docosenyl)-1,2-propanediol was the best QS inhibitor (20 μM), while (2S)-3-O-(cis-9’-hexadecenyl)-1,2-propanediol was the least effective (795 μM). The results showed for the first time the QSI activity of this natural AKG series and suggest that AKGs could be promising candidates for further studies on preventing antimicrobial resistance. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Article
New Functionalized Macroparticles for Environmentally Sustainable Biofilm Control in Water Systems
Antibiotics 2021, 10(4), 399; https://doi.org/10.3390/antibiotics10040399 - 07 Apr 2021
Viewed by 500
Abstract
Reverse osmosis (RO) depends on biocidal agents to control the operating costs associated to biofouling, although this implies the discharge of undesired chemicals into the aquatic environment. Therefore, a system providing pre-treated water free of biocides arises as an interesting solution to minimize [...] Read more.
Reverse osmosis (RO) depends on biocidal agents to control the operating costs associated to biofouling, although this implies the discharge of undesired chemicals into the aquatic environment. Therefore, a system providing pre-treated water free of biocides arises as an interesting solution to minimize the discharge of chemicals while enhancing RO filtration performance by inactivating bacteria that could form biofilms on the membrane system. This work proposes a pretreatment approach based on the immobilization of an industrially used antimicrobial agent (benzalkonium chloride—BAC) into millimetric aluminum oxide particles with prior surface activation with DA—dopamine. The antimicrobial efficacy of the functionalized particles was assessed against Escherichia coli planktonic cells through culturability and cell membrane integrity analysis. The results showed total inactivation of bacterial cells within five min for the highest particle concentration and 100% of cell membrane damage after 15 min for all concentrations. When reusing the same particles, a higher contact time was needed to reach the total inactivation, possibly due to partial blocking of immobilized biocide by dead bacteria adhering to the particles and to the residual leaching of biocide. The overall results support the use of Al2O3-DA-BAC particles as antimicrobial agents for sustainable biocidal applications in continuous water treatment systems. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Article
Can Vitamin B12 Assist the Internalization of Antisense LNA Oligonucleotides into Bacteria?
Antibiotics 2021, 10(4), 379; https://doi.org/10.3390/antibiotics10040379 - 03 Apr 2021
Viewed by 1128
Abstract
The emergence of bacterial resistance to traditional small-molecule antibiotics is fueling the search for innovative strategies to treat infections. Inhibiting the expression of essential bacterial genes using antisense oligonucleotides (ASOs), particularly composed of nucleic acid mimics (NAMs), has emerged as a promising strategy. [...] Read more.
The emergence of bacterial resistance to traditional small-molecule antibiotics is fueling the search for innovative strategies to treat infections. Inhibiting the expression of essential bacterial genes using antisense oligonucleotides (ASOs), particularly composed of nucleic acid mimics (NAMs), has emerged as a promising strategy. However, their efficiency depends on their association with vectors that can translocate the bacterial envelope. Vitamin B12 is among the largest molecules known to be taken up by bacteria and has very recently started to gain interest as a trojan-horse vector. Gapmers and steric blockers were evaluated as ASOs against Escherichia coli (E. coli). Both ASOs were successfully conjugated to B12 by copper-free azide-alkyne click-chemistry. The biological effect of the two conjugates was evaluated together with their intracellular localization in E. coli. Although not only B12 but also both B12-ASO conjugates interacted strongly with E. coli, they were mostly colocalized with the outer membrane. Only 6–9% were detected in the cytosol, which showed to be insufficient for bacterial growth inhibition. These results suggest that the internalization of B12-ASO conjugates is strongly affected by the low uptake rate of the B12 in E. coli and that further studies are needed before considering this strategy against biofilms in vivo. Full article
(This article belongs to the Special Issue New Insights on Biofilm Antimicrobial Strategies, 2nd Volume)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Displacement effects of lactobacilli against biofilms formed on urinary tract devices
Authors: Fábio M. Carvalho; Filipe J. M. Mergulhão; Luciana C. Gomes
Affiliation: LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

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