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Antibiotics
Special Issues
Innovative and Nonconventional Antimicrobial Strategies Against Multi-Resistant Bacteria
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Innovative and Nonconventional Antimicrobial Strategies Against Multi-Resistant Bacteria

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

Deadline for manuscript submissions: 15 September 2024 | Viewed by 2107

Special Issue Editor

Dr. Patrizia Casagrande-Proietti

E-Mail Website
Guest Editor
Associate Professor, Department Veterinary Medicine, Università degli Studi di Perugia, 06126 Perugia, Italy
Interests: antimicrobial resistance in zoonosic bacteria; phenotipic and genotipic characterization of antimicrobial-resistance mechanisms, including bacterial biofilm-forming ability; phenotypic and genetic mechanisms underlying the efflux-mediated resistance in zoonosic bacteria

Special Issue Information

Dear Colleagues,

The phenomenon of antibiotic resistance is one of the most significant public health problems to date. The ever-increasing emergence of multi-resistant microbial species in both animals and humans, as well as the limited efficacy of conventional antimicrobial therapies, means it is necessary to study new therapeutic strategies against multi-resistant bacteria. Thereby, this Special Issue is dedicated to the discovery of novel promising candidates for the future development of innovative, nonconventional antimicrobial agents against pathogenic bacteria of zoonotic and veterinary clinical interest. Moreover, this Special Issue promotes the study of natural compounds with a green and sustainable impact as antimicrobial agents and the investigation of their mechanisms of action.

Acknowledgment: Ms. Valeria Toppi will be participating in this Special Issue as a specialist advisor. We would like to thank her for her contributions to this Special Issue.

Dr. Patrizia Casagrande-Proietti
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at mdpi.longhoe.net 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

  • antibiotic resistance
  • multi-resistant bacteria
  • innovative agents
  • natural compound
  • green impact
  • veterinary medicine

Published Papers (2 papers)

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Research

11 pages, 2408 KiB  
Article
High Biofilm-Forming Multidrug-Resistant Salmonella Infantis Strains from the Poultry Production Chain
by Laura Musa, Valeria Toppi, Valentina Stefanetti, Noah Spata, Maria Cristina Rapi, Guido Grilli, Maria Filippa Addis, Giacomo Di Giacinto, Maria Pia Franciosini and Patrizia Casagrande Proietti
Antibiotics 2024, 13(7), 595; https://doi.org/10.3390/antibiotics13070595 - 27 Jun 2024
Viewed by 311
Abstract
The ability of Salmonella species to adhere to surfaces and form biofilms, leading to persistent environmental reservoirs, might represent a direct link between environmental contamination and food processing contamination. The purpose of this study was to investigate the biofilm-forming ability of 80 multidrug-resistant [...] Read more.
The ability of Salmonella species to adhere to surfaces and form biofilms, leading to persistent environmental reservoirs, might represent a direct link between environmental contamination and food processing contamination. The purpose of this study was to investigate the biofilm-forming ability of 80 multidrug-resistant (MDR) and extended-spectrum beta-lactamase (ESBL) producing Salmonella enterica serovar Infantis strains isolated from the broiler food chain production through whole genome sequencing (WGS), PCR, and morphotype association assays. Biofilm formation was quantified by testing the strains at two different temperatures, using 96-well polystyrene plates. The rough and dry colony (rdar) morphotype was assessed visually on Congo red agar (CRA) plates. Based on our results, all tested S. Infantis strains produced biofilm at 22 °C with an rdar morphotype, while at 37 °C, all the isolates tested negative, except one positive. Most isolates (58.75%) exhibited strong biofilm production, while 36.25% showed moderate production. Only 5 out of 80 (6.25%) were weak biofilm producers. WGS analysis showed the presence of the fim cluster (fimADF) and the csg cluster (csgBAC and csgDEFG), also described in S. Typhimurium, which are responsible for fimbriae production. PCR demonstrated the presence of csgD, csgB, and fimA in all 80 S. Infantis strains. To our knowledge, this is the first study comparing the effects of two different temperatures on the biofilm formation capacity of ESBL producing S. Infantis from the broiler production chain. This study highlights that the initial biofilm components, such as curli and cellulose, are specifically expressed at lower temperatures. It is important to emphasize that within the broiler farm, the environmental temperature ranges between 18–22 °C, which is the optimum temperature for in vitro biofilm formation by Salmonella spp. This temperature range facilitates the expression of biofilm-associated genes, contributing to the persistence of S. Infantis in the environment. This complicates biosecurity measures and makes disinfection protocols on the farm and in the production chain more difficult, posing serious public health concerns. Full article
(This article belongs to the Special Issue Innovative and Nonconventional Antimicrobial Strategies Against Multi-Resistant Bacteria)
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18 pages, 8895 KiB  
Article
Combination Therapy with Ciprofloxacin and Pentamidine against Multidrug-Resistant Pseudomonas aeruginosa: Assessment of In Vitro and In Vivo Efficacy and the Role of Resistance–Nodulation–Division (RND) Efflux Pumps
by Megan Fletcher, Alex McCormack, Benjamin J. Parcell and Peter J. Coote
Antibiotics 2023, 12(8), 1236; https://doi.org/10.3390/antibiotics12081236 - 26 Jul 2023
Cited by 2 | Viewed by 1471
Abstract
The aim of this work was to (i) evaluate the efficacy of a combination treatment of pentamidine with ciprofloxacin against Galleria mellonella larvae infected with an MDR strain of P. aeruginosa and (ii) determine if pentamidine acts as an efflux-pump inhibitor. Resistant clinical [...] Read more.
The aim of this work was to (i) evaluate the efficacy of a combination treatment of pentamidine with ciprofloxacin against Galleria mellonella larvae infected with an MDR strain of P. aeruginosa and (ii) determine if pentamidine acts as an efflux-pump inhibitor. Resistant clinical isolates, mutant strains overexpressing one of three RND efflux pumps (MexAB-OprM, MexCD-OprJ, and MexEF-OprN), and a strain with the same three pumps deleted were used. MIC assays confirmed that the clinical isolates and the mutants overexpressing efflux pumps were resistant to ciprofloxacin and pentamidine. The deletion of the three efflux pumps induced sensitivity to both compounds. Exposure to pentamidine and ciprofloxacin in combination resulted in the synergistic inhibition of all resistant strains in vitro, but no synergy was observed versus the efflux-pump deletion strain. The treatment of infected G. mellonella larvae with the combination of pentamidine and ciprofloxacin resulted in enhanced efficacy compared with the monotherapies and significantly reduced the number of proliferating bacteria. Our measurement of efflux activity from cells revealed that pentamidine had a specific inhibitory effect on the MexCD-OprJ and MexEF-OprN efflux pumps. However, the efflux activity and membrane permeability assays revealed that pentamidine also disrupted the membrane of all cells. In conclusion, pentamidine does possess some efflux-pump inhibitory activity, in addition to a more general disruptive effect on membrane integrity that accounts for its ability to potentiate ciprofloxacin activity. Notably, the enhanced efficacy of combination therapy with pentamidine and ciprofloxacin versus MDR P. aeruginosa strains in vivo merits further investigation into its potential to treat infections via this pathogen in patients. Full article
(This article belongs to the Special Issue Innovative and Nonconventional Antimicrobial Strategies Against Multi-Resistant Bacteria)
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