Antimicrobial activity of the rationally modified peptide KK12 and its evaluation in a cooked chicken challenge model inoculated with Salmonella enterica serovar Typhimurium

Abstract A peptide from black soldier fly larvae, KGNSELEEAKKK, was subjected to structural modifications through cationic and hydrophobic residues. The modified peptide KWWSKLKKFWKK (KK12), which had a net charge of +6 and 41.67% hydrophobic residues with tryptophan substitution, was the most potent peptide against salmonellosis-involving serotypes, particularly Salmonella Typhimurium TISTR 292, with a minimum inhibitory concentration (MIC) value of 2 µM as indicated by a microdilution assay. Scanning electron microscopy and transmission electron microscopy showed morphological changes and membrane disintegration in the KK12-treated cells, accompanied by DNA leakage as monitored at 260 nm. Synchrotron-based Fourier-transform infrared spectroscopy indicated that KK12 induced modifications of intracellular targets. KK12 showed a hemolytic rate of < 5% up to 16 µM and maintained comparable viability of Vero and HepG2 cell lines relative to untreated controls at concentrations up to 36 and 18 µM, which was approximately 8, 18 and 9 times, respectively, higher than its MIC, implying its safety for food and pharmaceutical applications. KK12 reduced the bacterial count on chicken meat surface inoculated with S. Typhimurium TISTR 292 with the maximum reduction of 1.09 log colony forming units (CFU) observed at 1.6 nmol (2.71 µg). These results indicated that KK12 could be a potential candidate for Salmonella control. Graphical Abstract