## 2 Results and Discussion
### AMP Type
#### 2.5.1 Single AMP Type
Class II piscidins (piscidin 4 and piscidin 5) were found to be more potently active against _Flavobacterium columnare_ and _E. coli_ than class I Piscidins (piscidin 1 and piscidin 3), but class I Piscidins showed more growth inhibition of _Aeromonas_ spp. [109]. With respect to synthetic derivatives of AMPs, [PERSON] et al. developed the new symmetric-end AMPs Lf6-pP and Lf6-GG (based on RRWQWRzzRWQQWR and centered on D-Pro-Pro) that exhibited potent antibacterial activity against _S. aureus_ (KCTC 1621) and _E. coli_ (KCTC 1682). Lf6-pP was effective in inhibiting biofilm formation and eradicating mature biofilms of MDR _P. aeruginosa_ (MDRPA) strain (CCARM 2095) [110]. The antibioticfilm activity of a previously designed AMP WLBU2 against _P. aeruginosa_ isolates was investigated by [PERSON] et al. [111]. WLBU2 significantly inhibited adhesion to a static abiotic solid surface and biofilm formation in all tested _P. aeruginosa_ strains. Additionally, exposure to WLBU2 resulted in a \(>\)4-fold reduction in biofilm-associated gene (e.g., rhll, rhR, lasl, and lasR) expression, while biofilm formation was significantly inhibited in a murine catheter-associated carbapenem-resistant _P. aeruginosa_ (CRPA) infection model. 'Unnatural' star-shaped AMPs were designed by [PERSON] et al. via homologues of poly(l-lysine) and poly(l-alpha,zeta-diaminoheptyllic acids). The star-shaped poly(l-ornithine) PO3 had high proteolytic stability and broad-spectrum antimicrobial activity especially against Gram-negative _P. aeruginosa_. In vivo studies using a _P. aeruginosa_-infected murine skin burn model revealed that PO3 alleviated inflammation and exhibited a wound healing process [112]. Using a different approach, [PERSON] et al. reported on 'the continued synthetic molecular evolution of a lineage of host-compatible AMPs' using variants derived from an evolved AMP, which was originally derived from a consensus sequence where two invariant glycines had been removed (termed 'D-amino acid CONsensus with Glycine Absent' or 'D-CONGA'). One variant (D-CONGA-Q7), with a polar glutamine inserted into the middle of the sequence, showed a 'gain of function' by being active against innately resistant clinical _K. pneumoniae_ isolates [113]. Bactencin from bovine neutrophils is one of the shortest natural broad-spectrum AMPs currently known. By attaching a hydrophobic fatty acid ligand to the AMP Bac8c (RIVIVWRR-NH2), the new LA-Bac8c demonstrated improved antibiofilm activity towards _S. aureus_ and MRSA compared to Bac8c [114]. Several publications focused on modifications of the human endogenous AMP LL-37. [PERSON] et al. generated a library of lipopeptides via sequential truncation of the AMP KR12 (derived from LL-37), which were also conjugated to fatty acids. They found that the miniature LL-37-like peptide C10-KR8d (d-form) was able to reduce MRSA bacterial burden in a neutropic mouse model. In addition, C10-KR8d prevented bacterial biofilm formation in an _S. aureus_ mouse catheter model [115]. AMP GA-KR12 (a short yet active peptide of LL-37) has novel dual-action activity that inhibits the growth of _S. mutans_ biofilm and promotes the remineralization of human dentine blocks with artificial carious lesions [116]. Dimerization and backbone cyclization of KR-12 facilitated the production of the synthetic peptide CD4-PP, which was active against type and clinical ureopathogenic strains of _K. pneumoniae_, _P. aeruginosa_, and _E. coli_. CD4-PP reduced _E. coli_ attachment to pieces of a urinary catheter placed in saline/CD4-PP fluid [117]. Interestingly, [PERSON] et al. compared the antibiofilm activities of a range of ceragenins(synthetic amphipatible molecules that are designed to mimic naturally occurring AMPs) against AMPs LL-37, magainin, and eccropin. At the concentrations tested, ceragenins (CSA-13, CSA-90) were reported to be much more effective against mono- and multi-species biofilms than AMPs, with them being particularly effective against _C. albicans_ biofilms [118].