Evaluation of the anti-biofilm efficacy of Kyotorphin derivatives and biosafety assessment: in vitro and in vivo investigations targeting bacterial and fungal pathogens

Kyotorphin (KTP) dipeptide (l-Tyrosine-l-Arginine) and their derivatives possess a multitude of functions, qualifying them as "multifunctional peptides." Considering the escalating bacterial resistance to antibiotics, antimicrobial peptides ofer a promising road, forming the central focus of this current investigation. The efectiveness of KTP derivatives, GABA-KTPNH2 and Indol-KTP-NH2, were assessed for bioflm inhibition in bacterial and fungal strains. The viability of these derivatives was tested in fbroblasts and B16-F10-Nex2 cells. In vivo toxicity was evaluated using the model organisms Galleria mellonella and Danio rerio. Notably, both GABA-KTP-NH2 and Indol-KTP-NH2 derivatives efectively hindered bioflm formation in E. coli, S. pneumoniae, and C. krusei. In the G. mellonella model, the derivatives exhibited signifcant larval survival rates in toxicity tests, while in infection tests, they demonstrated efcient treatment against the evaluated microorganisms. Conversely, zebrafsh assays revealed that Indol-KTP-NH2 induced substantial mortality rates in embryos after 72 and 96 h of exposure. Similarly, the GABA-KTP-NH2 derivative exhibited heightened lethality, noticeable at the 100 μM concentration after the same exposure periods. Importantly, toxicity assessments unveiled a relatively lower toxicity profle, coupled with a reduced potential for inducing abnormalities. These results highlight the necessity of employing a comprehensive approach that integrates diverse techniques to thoroughly assess toxicity implications.

Antimicrobial peptides properties beyond growth inhibition and bacterial killing.

Antimicrobial peptides (AMPs) are versatile molecules with broad antimicrobial activity produced by representatives of the three domains of life. Also, there are derivatives of AMPs and artificial short peptides that can inhibit microbial growth. Beyond killing microbes, AMPs at grow sub-inhibitory concentrations also exhibit anti-virulence activity against critical pathogenic bacteria, including ESKAPE pathogens. Anti-virulence therapies are an alternative to antibiotics since they do not directly affect viability and growth, and they are considered less likely to generate resistance. Bacterial biofilms significantly increase antibiotic resistance and are linked to establishing chronic infections. Various AMPs can kill biofilm cells and eradicate infections in animal models. However, some can inhibit biofilm formation and promote dispersal at sub-growth inhibitory concentrations. These examples are discussed here, along with those of peptides that inhibit the expression of traits controlled by quorum sensing, such as the production of exoproteases, phenazines, surfactants, toxins, among others. In addition, specific targets that are determinants of virulence include secretion systems (type II, III, and VI) responsible for releasing effector proteins toxic to eukaryotic cells. This review summarizes the current knowledge on the anti-virulence properties of AMPs and the future directions of their research.