Antibiofilm peptides as a promising strategy: comparative research

Biofilms lead to approximately 65% of infections, and these infections are hard to treat. Thus, it is crucial to identify effective antibiofilm agents with low cytotoxicity. Peptides with antibiofilm activity have been regarded as promising solutions, and peptides with MBICs (minimal biofilm inhibitory concentrations) that are lower than their minimal inhibitory concentration (MICs) (minimal inhibitory concentrations) are appealing. Therefore, we systematically summarized and classified previously reported peptides with antibiofilm activity. A total of 51 peptides with antibiofilm activity were classified into 14 categories. The MICs and MBICs of these fourteen representative peptides, one selected from each category, were compared against the Gram-positive bacterium Streptococcus mutans, the Gram-negative bacterium Pseudomonas aeruginosa, and the fungus Candida albicans. Six representative peptides (C5-pleurocidin, C6-Pac-525, C9-protegrin-1, C11-TetraF2W-RR, C13-WLBU2, and C14-melittin) showed antibiofilm activity against both bacteria and fungi, and among these 6 representative peptides, 4 peptides (C9-protegrin-1, C11-TetraF2W-RR, C13-WLBU2, and C14-melittin) could prevent biofilm formation with lower MBIC values than their MICs. CLSM (confocal laser scanning microscopy), SEM (scanning electron microscopy), and TEM (transmission electron microscopy) were further used to observe the morphologies of the biofilms after treatment with the peptides. Among the above 4 peptides, WLBU2 and melittin sparsely scattered the biofilms without destroying the bacteria. In conclusion, the currently reported peptides with antibiofilm activity are limited in number, but peptides with lower MBICs than MICs exist as promising candidates against biofilm-related infections and need further study. KEY POINTS: • Antibiofilm peptides could inhibit biofilm formation with MBICs that are lower than MICs. • The mechanism of antibiofilm peptides is not only due to antimicrobial activity.