Bacterial infection caused by intracellular pathogens, such as Mycobacterium, Salmonella, and Brucella, is a burgeoning global health epidemic that necessitates urgent action. However, the therapeutic value of a number of antibiotics, including aminoglycosides, against intracellular pathogenic bacteria is compromised due to their inability to traverse eukaryotic membranes. To address this significant problem, a cleavable conjugate of the antibiotic kanamycin and a non-membrane lytic, broad-spectrum antimicrobial peptide with efficient mammalian cell penetration, P14LRR, was prepared. This approach allows kanamycin to enter mammalian cells as a conjugate linked via a tether that breaks down in the reducing environment within cells. Potent antimicrobial activity of the P14KanS conjugate was demonstrated in vitro, and this reducible conjugate effectively cleared intracellular pathogenic bacteria within macrophage more potently than a conjugate lacking the disulfide moiety. Notably, successful clearance of Mycobacterium tuberculosis within macrophages was observed with the dual antibiotic conjugate, and Salmonella levels were significantly reduced in an in vivo Caenorhabditis elegans model.

No abstract

Antimicrobial peptides (AMPs) represent a promising therapeutic alternative for the treatment of antibiotic-resistant bacterial infections. The present study investigates the antimicrobial activity of new, rationally-designed derivatives of a short α-helical peptide, RR. From the peptides designed, RR4 and its D-enantiomer, D-RR4, emerged as the most potent analogues with a more than 32-fold improvement in antimicrobial activity observed against multidrug-resistant strains of Pseudomonas aeruginosa and Acinetobacter baumannii. Remarkably, D-RR4 demonstrated potent activity against colistin-resistant strains of P. aeruginosa (isolated from cystic fibrosis patients) indicating a potential therapeutic advantage of this peptide over several AMPs. In contrast to many natural AMPs, D-RR4 retained its activity under challenging physiological conditions (high salts, serum, and acidic pH). Furthermore, D-RR4 was more capable of disrupting P. aeruginosa and A. baumannii biofilms when compared to conventional antibiotics. Of note, D-RR4 was able to bind to lipopolysaccharide to reduce the endotoxin-induced proinflammatory cytokine response in macrophages. Finally, D-RR4 protected Caenorhabditis elegans from lethal infections of P. aeruginosa and A. baumannii and enhanced the activity of colistin in vivo against colistin-resistant P. aeruginosa.

This study demonstrates that equipping kanamycin with an antimicrobial peptide is a promising method to tackle bacterial biofilms and address bacterial resistance to aminoglycosides.

Das De‐novo‐Design nichtnatürlicher prolinreicher Peptide führt zu einem Wirkstoff gegen sowohl Gram‐positive als auch Gram‐negative Bakterien. Dieses Peptid löst weder bakterielle Membranen auf, noch bewirkt es eine Hämolyse; überdies ist es über längere Zeit gegen Trypsin stabil. Das leichte Eindringen in Makrophagen führt zu einer gründlichen Beseitigung pathogener Bakterien in diesen Zellen.