An Engineered Nisin Analogue with a Hydrophobic Moiety Attached at Position 17 Selectively Inhibits Enterococcus faecium Strains

Abstract

Antibiotic resistance is one of the most challenging global public health concerns. It results from the misuse and overuse of broad-spectrum antibiotics, which enhance the dissemination of resistance across diverse bacterial species. Antibiotics like nisin and teixobactin do not target an essential protein and employ a dual mode of action antibacterial mechanism, thereby being less prone to induce resistance. There is a need for the development of a potent narrow-spectrum dual-mode-acting antibiotic against human pathogens. Using nisin, a lantibiotic with potent antimicrobial activity against many pathogens, as a template, the unnatural amino acid azidohomoalanine was introduced at selected positions and subsequently modified using click chemistry with 14 alkyne-moiety containing tails. A novel nisin variant, compound 47, featuring a benzyl group-containing tail, exhibited potent activity against various (drug-resistant) E. faecium strains with an MIC value (3.8 mg/L) similar to nisin, whereas its activity toward other pathogens like Staphylococcus aureus and Bacillus cereus was significantly reduced. Like nisin, the mode of action of compound 47 results from the inhibition of cell wall synthesis by binding to lipid II and nisin–lipid II hybrid-pore formation in the outer membrane. The resistance of compound 47 against proteolytic degradation is markedly enhanced compared to nisin. Like nisin, compound 47 was hardly hemolytic even at a very high dose. Collectively, a modified nisin variant is presented with significantly enhanced target organism specificity and stability.