*Review* **Our Experience over 20 Years: Antimicrobial Peptides against Gram Positives, Gram Negatives, and Fungi**

**Giulio Rizzetto 1,†, Daisy Gambini 1,†, Andrea Maurizi 1, Matteo Candelora 1, Elisa Molinelli 1, Oscar Cirioni 2, Lucia Brescini 2, Andrea Giacometti 2, Annamaria Offidani <sup>1</sup> and Oriana Simonetti 1,\***


**Abstract:** Antibiotic resistance is rapidly increasing, and new anti-infective therapies are urgently needed. In this regard, antimicrobial peptides (AMPs) may represent potential candidates for the treatment of infections caused by multiresistant microorganisms. In this narrative review, we reported the experience of our research group over 20 years. We described the AMPs we evaluated against Gram-positive, Gram-negative, and fungi. In conclusion, our experience shows that AMPs can be a key option for treating multiresistant infections and overcoming resistance mechanisms. The combination of AMPs allows antibiotics and antifungals that are no longer effective to exploit the synergistic effect by restoring their efficacy. A current limitation includes poor data on human patients, the cost of some AMPs, and their safety, which is why studies on humans are needed as soon as possible.

**Keywords:** anti-microbial peptides; antibiotic resistance; Gram-positive Gram-negative; fungi

**Citation:** Rizzetto, G.; Gambini, D.; Maurizi, A.; Candelora, M.; Molinelli, E.; Cirioni, O.; Brescini, L.; Giacometti, A.; Offidani, A.; Simonetti, O. Our Experience over 20 Years: Antimicrobial Peptides against Gram Positives, Gram Negatives, and Fungi. *Pharmaceutics* **2022**, *15*, 40. https://doi.org/10.3390/ pharmaceutics15010040

Academic Editors: Scavello Francesco, Amiche Mohamed and Jean-Eric Ghia

Received: 26 October 2022 Revised: 4 December 2022 Accepted: 12 December 2022 Published: 22 December 2022

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).
