Peptídeos antimicrobianos derivados da toxina de artrópodes como potenciais fármacos contra bactérias multirresistentes: eficácia in vitro e in vivo, toxicidade e formulação farmacêutica.

Abstract

The emergence of antibiotic-resistant bacteria, dubbed superbugs, together with relative stagnation in developing efficient antibiotics has led to enormous health and economic problems, necessitating the need for discovering and developing novel antimicrobial agents. In this respect, animal venoms represent a rich repertoire of pharmacologically active components that can be exploited in the development of new antibiotics. Melittin is the major component in bee venom (Apis mellifera) and has great potential in medical applications, especially as an antibacterial agent. In addition, derivatives of the toxin of the Aranha-de-Jardim (Lycosa erythrognatha), such as the peptide LyeTx mnΔK, are highly active against multidrug-resistant Gram-negative bacteria. In this study, we aimed to carry out an in-depth characterization of the anti staphylococcal and anti-Escherichia coli effect of melittin using multidrug-resistant clinical isolates of these pathogens. We also aim to describe the antibacterial spectrum of LyeTx I mnΔK against carbapenem-resistant Acinetobacter baumannii (CRAB) and to prospect the use of this compound in pneumonia caused by this pathogen. Melittin revealed a potent antibacterial effect against Staphylococcus spp. (MIC 0.12-4 µM) and uropathogenic Escherichia coli (UPEC) (MIC 0.5-8 µM). Furthemore, it showed a fast (0.5h) bactericidal activity, being active against planktonic, stationary, and persistent cells. Similarly, melittin exhibited the ability to kill quinolone-resistant and extended-spectrum beta-lactamase (ESBL) producing UPEC cells in vitro (CBM 1-32 µM). In the tested concentration range (8-32 µM), melittin significantly reduces the mature MRSA biofilm, and it was able to lyse the cells of this pathogen. The combination of melittin with conventional antibiotics produced a synergistic effect, and this peptide re-sensitize MRSA to the action of amoxicillin, ceftizoxime, and vancomycin. For quinolone-resistant and ESBL-producing UPECs, the results were similar, with melittin inhibiting the formation of biofilms in urethral catheter and re sensitizing the action of beta-lactams against this bacterium. The treatment of MRSA-induced wounds with an ointment containing melittin resulted in a significant reduction in the bacterial load and a considerable reduction of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β). LyeTx I mnΔK also showed considerable antibacterial activity against extensively resistant A. baumannii, with MIC and MBC ranging from 1 to 16 µM and 2 to 32 µM, respectively. Similar to melittin, LyeTx I mnΔK interacts synergistically and re-sensitize CRAB cells to the effects of commercial antibiotics, in addition to disrupting mature biofilms formed by this Gram-negative pathogen. The cytotoxic concentration of LyeTx I mnΔK (CC50 = 9.40±2.84 µM) against Vero cells was similar to that of colistin (CC50 = 15.42±2.73 µM), and its hemolytic activity was considerably low (HC50 = 77.07±4.00 µM). The oral and plasmatic stability of LyeTx I mnΔK is very low. Nevertheless, the inhalation of this peptide proved to be effective in the reduction of pulmonary bacterial load in a mouse model of CRAB infection. Together, the results of this study highlight that the melittin and the peptide LyeTx I mnΔK are potential prototypes in the development of new antibacterial agents against multidrug-resistant pathogens of clinical relevance.