Antibiotic Resistance in Biofilm: 2nd Edition

A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Microbiology".

Deadline for manuscript submissions: 16 June 2025 | Viewed by 7320

Special Issue Editor

Faculty of Veterinary Medicine, Banat's University of Agricultural Sciences and Veterinary Medicine "King Michael I of Romania" Timișoara, 300642 Timișoara, Romania
Interests: food safety; food quality; microbial biofilm; antibiotic resistance; pathogenic bacteria
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Biofilm is a complex group of microorganisms that attaches to solid surfaces in humid environments. It is characterized by structural heterogeneity, genetic diversity, complex interactions, and an extracellular matrix of polymeric substances. Biofilm provides the component microorganisms for certain nutrients, trace elements, and water, and helps to protect against harmful factors, including biocides. Thus, biofilm is commonly found in the food industry, as well as in wet processing conditions (e.g., dairy products, slaughterhouses, meat-processing plants, beverages industry, etc.), and can act as a reservoir for germs with pathogenic potential for humans and animals.

Both pathogenic and non-pathogenic microorganisms can be embedded in biofilm structures. Occasionally, parts of the biofilm may be removed and spread in moist environments, resulting in subsequent contamination of other surfaces.

Bacteria embedded in biofilm are more resistant to antimicrobials compared to planktonic cells. The increase in bacterial resistance to antibiotics is due to several mechanisms. One of these is the different structure of the internal biofilm, which generates the unequal diffusion of antimicrobials. Consequently, bacterial cells will be exposed to different concentrations of antibiotics, depending on their spatial location, which favors the selection of cells with mutational antimicrobial resistance. Another factor is the increase in conjugation frequency due to the proximity of the cells in the biofilm structures, enhancing the spread of antibiotic resistance. 

In this Special Issue, advances in understanding the role of bacterial biofilms in antibiotic resistance in the food industry and the necessary control strategies will be presented.

This Special Issue's first edition was a great achievement. We are now inviting you to contribute to the second edition. (https://www.mdpi.com/journal/life/special_issues/Biofilm_life).

Dr. Adriana Morar
Guest Editor

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Keywords

  • biofilm
  • food industry
  • antimicrobial resistance
  • antibiotic resistance gene transfer
  • antibiofilm activity
  • control strategies

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Published Papers (4 papers)

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Research

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16 pages, 1373 KiB  
Article
Effects of Sequential Antimicrobial Phases on Root Canal Microbiome Dynamics in Two-Visit Treatment of Primary Apical Periodontitis: A Longitudinal Experimental Study
by Bertan Kesim, Seda Tezcan Ülger, Gönül Aslan, Yakup Üstün, Ayşe Tuğba Avcı and Mustafa Öner Küçük
Life 2024, 14(12), 1696; https://doi.org/10.3390/life14121696 - 21 Dec 2024
Viewed by 957
Abstract
Background: Effective management of primary apical periodontitis depends on understanding the dynamic interactions within the root canal microbiome. This study aimed to investigate the effect of sequential antimicrobial phases on the root canal microbiome during a two-visit treatment approach, with a focus on [...] Read more.
Background: Effective management of primary apical periodontitis depends on understanding the dynamic interactions within the root canal microbiome. This study aimed to investigate the effect of sequential antimicrobial phases on the root canal microbiome during a two-visit treatment approach, with a focus on calcium hydroxide medication. Methods: Samples were collected from three teeth across four treatment phases: initial infection (S1), after chemomechanical preparation (S2), after intracanal medication (S3), and after a final flush (S4). DNA was extracted, and the V3–V4 regions of the 16S rRNA gene were sequenced using Illumina MiSeq. Sequencing data were analyzed with QIIME 2, and differentially abundant taxa were identified using linear discriminant analysis effect size (LEfSe). Results: While microbial community composition did not differ significantly between phases, the Firmicutes/Bacteroidetes ratio decreased after the antimicrobial stages. LEfSe analysis revealed higher abundances of Lactobacillales, Arthrobacter, and Veillonella in the untreated (CMP) group. Bifidobacterium longum was relatively more abundant in the intracanal medication (ICM) phase, and Dorea formicigenerans was more abundant in the final-flush (FF) phase. Conclusions: Although calcium hydroxide treatment did not induce statistically significant changes in overall root canal microbial composition, trends such as a reduction in the Firmicutes/Bacteroidetes ratio and a relative increase in Bifidobacterium longum numbers suggest potential ecological shifts. The observed relative increase in Bifidobacterium longum numbers may represent a hypothesis-driven observation reflecting indirect ecological effects rather than direct pH modulation. While visual patterns (e.g., PCA clustering) were observed, they lacked statistical support. Further studies with larger sample sizes are needed to validate these observations and assess the potential role of beneficial bacteria in root canal treatments. Full article
(This article belongs to the Special Issue Antibiotic Resistance in Biofilm: 2nd Edition)
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11 pages, 2793 KiB  
Article
Quaternary Ammonium Silica Nanoparticles for Antimicrobial Implantable Medical Devices: An In Vitro Study
by Eitam Weiss, Ariel Berl, Ofir Shir-az, Biader Samih Bilal, Ervin I. Weiss, Yossi Paitan, Natan Zaltsman, Alexander Golberg and Avshalom Shalom
Life 2024, 14(12), 1654; https://doi.org/10.3390/life14121654 - 12 Dec 2024
Viewed by 1007
Abstract
Biofilm formation on prostheses and implanted devices can lead to serious complications and increased healthcare expenditures. Once formed, biofilm management is difficult and may involve a long course of antibiotics, additional surgery, and, occasionally, implant removal. This study evaluated the antibacterial properties of [...] Read more.
Biofilm formation on prostheses and implanted devices can lead to serious complications and increased healthcare expenditures. Once formed, biofilm management is difficult and may involve a long course of antibiotics, additional surgery, and, occasionally, implant removal. This study evaluated the antibacterial properties of medical-grade silicone samples integrated with novel, non-leaching, antibacterial, quaternary ammonium silica (QASi) particles. Our collaborators (Nobio, Israel) prepared silicone sheets integrated with antibacterial QASi nanoparticles. Samples containing 0.5%, 0.75%, and 1%, QASi particles were evaluated for antibacterial properties against S. epidermidis, S. aureus, methicillin-resistant S. aureus (MRSA), E. faecalis, and P. aeruginosa using the direct contact test. The tested silicone samples integrated with QASi particles showed no bacterial growth, while growth was observed in control silicone samples without QASi. In addition, the agar diffusion test, used to evaluate the leaching of antibacterial components, exhibited no inhibition zone around the samples indicating that the QASi particles do not leach into surrounding milieu. The QASi nanoparticles exhibited very potent antibacterial surface properties, killing all viable bacteria placed on their surface. Incorporating QASi nanoparticle technology into medical products during production has the potential to create an antimicrobial surface that prevents microbial colonization and biofilm formation. Full article
(This article belongs to the Special Issue Antibiotic Resistance in Biofilm: 2nd Edition)
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Review

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23 pages, 1855 KiB  
Review
Biochemistry of Bacterial Biofilm: Insights into Antibiotic Resistance Mechanisms and Therapeutic Intervention
by Kashish Azeem, Sadaf Fatima, Asghar Ali, Ayesha Ubaid, Fohad Mabood Husain and Mohammad Abid
Life 2025, 15(1), 49; https://doi.org/10.3390/life15010049 - 2 Jan 2025
Cited by 3 | Viewed by 2673
Abstract
Biofilms, composed of structured communities of bacteria embedded in a self-produced extracellular matrix, pose a significant challenge due to their heightened resistance to antibiotics and immune responses. This review highlights the mechanisms underpinning antibiotic resistance within bacterial biofilms, elucidating the adaptive strategies employed [...] Read more.
Biofilms, composed of structured communities of bacteria embedded in a self-produced extracellular matrix, pose a significant challenge due to their heightened resistance to antibiotics and immune responses. This review highlights the mechanisms underpinning antibiotic resistance within bacterial biofilms, elucidating the adaptive strategies employed by microorganisms to withstand conventional antimicrobial agents. This encompasses the role of the extracellular matrix, altered gene expression, and the formation of persister cells, contributing to the recalcitrance of biofilms to eradication. A comprehensive understanding of these resistance mechanisms provides a for exploring innovative therapeutic interventions. This study explores promising avenues for future research, emphasizing the necessity of uncovering the specific genetic and phenotypic adaptations occurring within biofilms. The identification of vulnerabilities in biofilm architecture and the elucidation of key biofilm-specific targets emerge as crucial focal points for the development of targeted therapeutic strategies. In addressing the limitations of traditional antibiotics, this review discusses innovative therapeutic approaches. Nanomaterials with inherent antimicrobial properties, quorum-sensing inhibitors disrupting bacterial communication, and bacteriophages as biofilm-specific viral agents are highlighted as potential alternatives. The exploration of combination therapies, involving antimicrobial agents, biofilm-disrupting enzymes, and immunomodulators, is emphasized to enhance the efficacy of existing treatments and overcome biofilm resilience. Full article
(This article belongs to the Special Issue Antibiotic Resistance in Biofilm: 2nd Edition)
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25 pages, 2508 KiB  
Review
Unusual and Unconsidered Mechanisms of Bacterial Resilience and Resistance to Quinolones
by Joaquim Ruiz
Life 2024, 14(3), 383; https://doi.org/10.3390/life14030383 - 14 Mar 2024
Viewed by 2062
Abstract
Quinolone resistance has been largely related to the presence of specific point mutations in chromosomal targets, with an accessory role of impaired uptake and enhanced pump-out. Meanwhile the relevance of transferable mechanisms of resistance able to protect the target of pump-out or inactivate [...] Read more.
Quinolone resistance has been largely related to the presence of specific point mutations in chromosomal targets, with an accessory role of impaired uptake and enhanced pump-out. Meanwhile the relevance of transferable mechanisms of resistance able to protect the target of pump-out or inactivate quinolones has been increasingly reported since 1998. Nevertheless, bacteria have other strategies and mechanisms allowing them to survive and even proliferate in the presence of quinolones, which might be qualified as resistance or resilience mechanisms. These include decreasing levels of quinolone target production, transient amoeba protection, benthonic lifestyle, nutrient-independent slow growth, activation of stringent response, inactivation or degradation of quinolones as well as apparently unrelated or forgotten chromosomal mutations. These mechanisms have been largely overlooked, either because of the use of classical approaches to antibiotic resistance determination or due to the low increase in final minimum inhibitory concentration levels. This article is devoted to a review of a series of these mechanisms. Full article
(This article belongs to the Special Issue Antibiotic Resistance in Biofilm: 2nd Edition)
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