Atividade antimicrobiana e antibiofilme do peptídeo kr-12 e seu análogo [w7]kr12-kaek contra bactérias relacionadas à patologias orais

Abstract

The oral microbiota is rich in different species of bacteria, fungi and viruses. Generally, these microorganisms coexist in a balanced environment for mutual benefit. However, when environmental, individual or microbiological factors cause disorders, such microbiota can be changed causing the appearance of diseases such as caries, periodontal disease and endodontic lesions. Currently, a group of bioactive molecules has attracted the attention of researchers because of its spectrum of action and biocompatibility, these are the antimicrobial peptides (AMPs). Among the several varieties of peptides, the ones related to the human immune system, such as KR-12, are the most widely studied, serving as a basis for the development of new synthetic peptide with greater biological activity and biocompatibility. Thus, the objective of this study was to evaluate the antimicrobial and antibiofilm potential of the synthetic peptide [W7]KR12-KAEK on bacteria related to the development of oral diseases. To achieve this purpose, antibacterial assays were developed on planktonic cells and biofilms. Moreover, the peptide effect on preformed biofilms were analysed by scanning electron microscopy. For the tests performed, the species used were S. sanguinis ATCC 10556, S. sobrinus ATCC 6715, S. oralis ATCC 10557, S. salivarius ATCC 7073, S. parasanguinis ATCC 903, S. mutans ATCC 25175, S. mutans UA 159, S. mutans UA 130, E. faecalis ATCC 10100 and E. faecalis ATCC 19433. All strains were standardized for the cell concentration of 2x106 CFU/ml. For antimicrobial analysis, bacterial strains were subjected to the technique of microdilution in microtiter plates to achieve the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). For antibiofilm activity assays, were analyzed the biomass quantification by crystal violet and the counting of colony forming units on developing biofilms and preformed biofilms. The use of scanning electron microscopy (SEM) for morphological analysis was performed only for preformed biofilms. Regarding the activity against planktonic bacteria, synthetic peptide tested showed significant antibacterial effect for all strains tested, with MIC values ranging between 7.8 and 31.25 µg/mL and MBC values between 15.6 and 62.5 µg/ml. For biofilms tests, [W7]KR12-KAEK showed a reduction in biomass and CFU's number for all tested bacteria, even in mature biofilm assays. The visualization by SEM showed that, at the concentration of 500 µg/ml, the peptide caused a morphological change in the bacterial surface of S. mutans UA130 and E. faecalis ATCC19433 (single strains used for this analysis) and reduced the number of embedded cells in the biofilm. Finally, it was concluded that the peptide [W7]KR12-KAEK has effective antimicrobial and antibiofilm activity against all strains evaluated. The peptide has a biotechnological potential for incorporation into dental use products to treat oral disorders related to bacteria of the genus Streptococcus and Enterococcus.