Drug Delivery Systems against Microorganisms: Status and Prospects

Dear Colleagues,

World human population, exceeding 7.9 billion people, and domestic animals -including pets (between 470-900 million dogs and ca. 370 million cats) and livestock (19.6 billion chicken, 1.4 billion cows, 2.2 billion goats & sheep and 980 million pigs)- can be colonized and, eventually, diseased by microorganisms (bacteria, fungi, protozoa). Well before naming the One Health framework, medical doctors and veterinarians were aware of the relevance of considering human and animal health jointly. Availability of antimicrobial therapy, in particular antibiotics, has shaped human societies but the combination of their efficacy, unjustified massive use, inadequate treatment regimens and selection pressure on bacteria have provoked the appearance of resistance phenomena along the environmental impact of the huge amounts produced (e.g.  93,309 tons of antibiotics active ingredient were produced in 2017).  Antibiotic medication was considered a must in animal production although the development of antibiotic resistance -both in humans and animals- and the zoonotic transmission of some bacterial species prompted to reduce the use of antibiotics in most managerial systems in developed countries (47% decrease between 2011 and 2021).

Diseases caused by protozoans and fungi also have inconveniences for being treated. Current chemotherapy against some infections has important drawbacks and there still are infections without any available treatment. Resistant strains are increasingly reported in some of the more devastating human infections (e.g. malaria, visceral leishmaniasis), and toxicity associated to many treatments is a severe constraint to their practical use in routine practice. In veterinary medicine, both in livestock and pets, the situation is comparable. To make matters worse, neither the exploration of unique metabolic pathways of microbial pathogens nor the synthesis of new chemical entities (NCE) efficacious against bacteria, protozoans and fungi have significantly increased our therapeutical store. Thus, new antimicrobial molecules and targeted administration of the available ones are required.

Drug delivery systems (DDS) have a number of potential advantages (e.g. reduction of toxicity, more effective drug targeting, reduction of administered dose) and a variety of technological approaches have been developed and tested. Moreover, this concept can be extended to the in-site delivery of vaccines, the design of slow-release devices providing sustained effective drug levels thus avoiding the risk of subtherapeutical dosing, non-invasive administration of antimicrobial agents (e.g. transdermal treatment; micro-needle devices), incorporation of nanotechnological systems, or the development of composite pills (e.g. layered tablets) with drug precursors among other approaches. This research field is very active and some new DDS have been already marketed and new approaches are being explored for currently available drugs and potential NCE as well.

Contributions to the Special Issue will be mainly focused -but not restricted to- on research work performed or reviews on:

• Clinical studies involving the treatment of bacterial, fungal or protozoal diseases, in humans and animals using DDS.
• Testing of DDS of antimicrobials in vitro, ex vivo or in vivo, in target species and surrogate models.
• Pharmacological and toxicological studies with antimicrobials in DDS in human and animals.
• Development of improved or new DDS for antimicrobial molecules.

Overall, this special issue, “Drug delivery systems (DDS) against microorganisms: status and prospects” aims to offer a faithful picture of the present situation and new developments, through the open access publication, of the state-of-the-art of DDS in the treatment of microbial infections. We hope that you find this proposal interesting and could contribute with your valuable work. Thanks.

Prof. Dr. José María Alunda
Prof. Dr. Juan José Torrado
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 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. Microorganisms 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 2700 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.