# Biofilms: Novel Strategies Based on Antimicrobial Peptides
## 3 Antimicrobial Peptides as Anti-Biofilm Agents
[44] showed that phylloseptin-PTa and phylloseptin-PHa isolated from _Phyllomedusa tarsius_ and _Phyllomedusa hypochondrialis_ have antimicrobial activities against Gram-positive bacteria (such as _Staphylococcus aureus_ and _Enterococcus faecalis_) and methicillin-resistant _Staphylococcus aureus_. [PERSON] et al. [45] have extracted from the secretion of _Pelophyllax l. esculentus_ skin the temperorin-PE, a potent AMP (Table 1). Modifications of this peptide introducing short sequences, as TAT, at C-terminus or modifications of FLP motif produced variations of its activity. [PERSON] et al. [46] isolated andricin B from the blood of _A. davidianus_ by a new method which implied the magnetic liposome adsorption combined with reversed-phase high-performance liquid chromatography. Andricin B is active against all bacteria tested and some fungi. The MICs were in the range 8-64 \(\upmu\)g/mL. Moreover, the hemolytic tests indicated that andricin B is safe at the MICs at which it inhibits the growth of _S. aureus_. [PERSON] et al. [47] isolated Japonic-2 LF from the skin mucus of _Limonetces fujianensis_ through the combination of cDNA cloning and MS/MS sequencing. The activity of this peptide was evaluated with different methods. They used the _Galferia mellonella_ infection model to assess the efficacy of Japonic-2 LF. This peptide showed great antimicrobial activity against _S. aureus_ and MRSA, killing the bacteria via membrane permeabilization. Japonic-2 LF acts through inhibition and removal of \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **Amphibian AMPs Production** & \\ \hline
**Species** & **Family** & **Peptide** & **Effects** & **Pathogens** \\ \hline _X. laevis_ & pipidae & XLAsp-P1 & haemolytic activity, destruction of the membrane & Gram-positive and Gram-negative \\ \hline _L. infrarenata_ & Hylidae & frenatin 4.1 frenatin 4.2a & antimicrobial activities & all bacteria tested \\ \hline _P. hypochondrialis_ & Hylidae & Dermaseptin-PH & inhibition of the growth & Gram-negative and Gram-positive _Candidia albicans_ \\ \hline _P. tarsius_ & Hylidae & phylloseptin-PTa and phylloseptin-PTa & antimicrobial activities & _S. aureus_, _E. faecalis_ \\ \hline _P. hl. esculentus_ & Ranidae & temporin-PE & antimicrobial activities & antimicrobial activities \\ \hline _A. davidianus_ & Cryptobranchidae & andricin B & antimicrobial activities & all bacteria tested and some fungi _Staphylococcus aureus_ \\ \hline _L. finjianensis_ & Dicroglossidae & Japonic-2 LF & membrane permeabilization & _S. aureus_ and MRSA \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Schematic representation of some AMP extracted by amphibian. biofilms, especially against MRSA biofilm. In vivo studies indicated that Japonicin-2 LF is a potential candidate to control the MRSA infection in cystic fibrosis patients. Most anti-biofilm peptides work at concentrations equal or higher than their MIC but there are some peptides that showed their action also at concentration much lower than MIC interfering with the biofilm life-style and displaying that the optimal antimicrobial activity against planktonic cells does not necessarily coincide with an optimal anti-biofilm effect. In other words, anti-biofilm activity is not necessarily correlated to antimicrobial activity. Generally, the minimal biofilm inhibiting concentration (MBIC) of AMPs is much lower than minimal inhibitory concentration of bacterial growth (MIC). Sometimes they prevent the intracellular accumulation of secondary messenger nucleotide molecules (ppGpp, c-d-GMP) which are involved in many metabolic steps such as colonization, adhesion, and communication in Gram-positive and Gram-negative bacteria [14]. Extracellular DNA (e-DNA) is a major component of bacteria and fungi biofilm.