# Biofilms: Novel Strategies Based on Antimicrobial Peptides
## 3 Antimicrobial Peptides as Anti-Biofilm Agents
In vivo studies demonstrated that biofilms are also capable of escaping host immune responses leading to an intense host pro-inflammatory response, which contributes to tissue damage and a lower action of macrophages [27]. Another required property for anti-biofilm agents is the capability of balancing the pro-inflammatory and anti-inflammatory immune cell responses. AMPs can be divided mainly into two groups: natural and synthetic. Natural AMPs are part of the natural anti-inflammatory and antimicrobial system and display a synergistic effect with antibiotics; they represent a source of inspiration for the design of synthetic AMPs and their main disadvantageis the high instability due to the rapid degradation and easy cleavage by proteases. To increase the potential of therapeutic applications of AMPs, novel chemically modified analogues have been synthetized to enhance their pharmacological properties [28; 29; 30; 31]. Most AMPs are toxic to bacteria but not to eukaryotes owing to the different membrane organization of bacteria and multicellular organisms [23; 32]. Moreover, they present different and faster killing mechanisms compared to conventional antibiotics because exploiting the disruption and permeabilization of microbial cell membranes. Among natural AMPs, those derived from amphibians certainly hold great promise; in fact, the amphibians present a surprisingly diverse population of antimicrobial peptides [33]. New AMPs  
Figure 1: Biofilms develop in three phases: initial adhesion, maturation, and dispersion. A good anti-biofilm agent (blue peptide) can be involved in all the biofilm phases. AMPs may inhibit the accumulation of bacteria on the surface by interacting with their adhesion proteins (red and light blue) or coating the surface to protect from bacterial attack. Antimicrobial peptides can display an action against bacteria in their active state in the biofilm (brown); they can also defeat bacteria in the persisters models (yellow) or interfere with life processes such as synthesis of EPS (light green matrix), signaling compounds (triangle), extracellular DNA, and proteins (green helix). are isolated from amphibian secretions, which are mainly produced in their skin granular glands and are released following stress or injury [34; 35].They have received great attention in recent years and as a matter of fact, more than a thousand of amphibian peptides are deposited in Antimicrobial Peptide Database [36; 37; 38]. Because their innate resistance to bacterial infections the amphibians have been studied since the 1930s [39] and in 1987, for the first time, [PERSON] extracted two potent nonhemolytic antimicrobial peptides from _X. laevis_ skin [40]. AMPs are frequently isolated from amphibians as a mold to produce synthetic analogues to fight biofilms. Here we list some amphibian AMPs isolated in recent years. [PERSON] et al. [41] isolated a small anionic antibacterial peptide from _X. laevis_ secretions (XLAsp-P1). XLAsp-P1 showed high activity in vitro against a great number of Gram-positive and Gram-negative bacteria with MIC starting at 10 \(\upmu\)g/mL. Moreover, it shows only 6.2% of hemolytic activity when used at 64 \(\upmu\)g/mL. This peptide acts on the membrane. [PERSON] et al. [42] used the skin secretion of _Litoria infrarenata_ to discover peptides with therapeutic potential; they cloned a frenatin gene and identified the peptide frenatin 4.1 and a post-translation modified peptide, frenatin 4.2. Moreover, they designed analogues that exhibited enhanced antimicrobial activities as frenatin 4.2a. [PERSON] et al. [43] extracted from the mucus of _Phyllomedusa hypochondrialis_, Dermaseptin-PH, and investigated its antimicrobial activity. Dermaseptin-PH inhibited the growth of both Gram-negative and Gram-positive bacteria and of _C. albicans_. [PERSON] et al.