Antibacterial activity of a novel antimicrobial peptide [W7]KR12-KAEK derived from KR-12 against Streptococcus mutans planktonic cells and biofilms.

The aims of this study were to describe the synthesis of a novel synthetic peptide based on the primary structure of the KR-12 peptide and to evaluate its antimicrobial and anti-biofilm activities against Streptococcus mutans. The antimicrobial effect of KR-12 and [W]KR12-KAEK was assessed by determining the minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations. The evaluation of anti-biofilm activity was assessed through total biomass quantification, colony forming unit counting and scanning electron microscopy. [W]KR12-KAEK showed MIC and MBC values ranging from 31.25 to 7.8 and 62.5 to 15.6 μg ml, respectively. Furthermore, [W7]KR12-KAEK significantly reduced biofilm biomass (50-100%). Regarding cell viability, [W]KR12-KAEK showed reductions in the number of CFUs at concentrations ranging from 62.5 to 7.8 μg ml and 500 to 62.5 μg ml with respect to biofilm formation and preformed biofilms, respectively. SEM micrographs of S. mutans treated with [W]KR12-KAEK suggested damage to the bacterial surface. [W]KR12-KAEK is demonstrated to be an antimicrobial agent to control microbial biofilms.