title: Anti-mycobacterial activities of synthetic cationic α-helical peptides and their synergism with rifampicin.
abstract: The rapid emergence of multi-drug resistant tuberculosis (TB) and the lack of effective therapies have prompted the development of compounds with novel mechanisms of action to tackle this growing public health concern. In this study, a series of synthetic cationic α-helical antimicrobial peptides (AMPs) modified with different hydrophobic amino acids was investigated for their anti-mycobacterial activity, both alone and in synergistic combinations with the frontline anti-tuberculosis drug rifampicin. The addition of thiol groups by incorporating cysteine residues in the AMPs did not improve anti-mycobacterial activity against drug-susceptible and drug-resistant Mycobacterium tuberculosis, while the enhancement of peptide hydrophobicity by adding methionine residues increased the efficacy of the primary peptide against all strains tested, including clinically isolated multidrug-resistant mycobacteria. The peptide with the optimal composition M(LLKK)2M was bactericidal, and eradicated mycobacteria via a membrane-lytic mechanism as demonstrated by confocal microscopic studies. Mycobacteria did not develop resistance after multiple exposures to sub-lethal doses of the peptide. In addition, the peptide displayed synergism with rifampicin against both Mycobacterium smegmatis and Mycobacterium bovis BCG and additivity against M. tuberculosis. Moreover, such combination therapy is effective in delaying the emergence of rifampicin resistance. The ability to potentiate anti-TB drug activity, kill drug-resistant bacteria and prevent drug resistance highlights the potential utility of the peptide in combating multidrug-resistant TB.
authors: Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Singapore 117543, Singapore.
authors: Jasmeet S
authors: JS
authors: Khara
authors: Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Singapore 117543, Singapore.
authors: Ying
authors: Y
authors: Wang
authors: Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, Singapore 138669, Singapore.
authors: Xi-Yu
authors: XY
authors: Ke
authors: Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, Singapore 138669, Singapore.
authors: Shaoqiong
authors: S
authors: Liu
authors: Section of Paediatrics, Division of Medicine, St Mary's Campus, Imperial College, London W2 1PG, United Kingdom.
authors: Sandra M
authors: SM
authors: Newton
authors: Section of Paediatrics, Division of Medicine, St Mary's Campus, Imperial College, London W2 1PG, United Kingdom.
authors: Paul R
authors: PR
authors: Langford
authors: Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, Singapore 138669, Singapore. Electronic address: yyyang@ibn.a-star.edu.sg.
authors: Yi Yan
authors: YY
authors: Yang
authors: Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Singapore 117543, Singapore. Electronic address: phaeplr@nus.edu.sg.
authors: Pui Lai Rachel
authors: PL
authors: Ee
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004357:Drug Synergism; D009163:Mycobacterium bovis / Q000187:drug effects; D020102:Mycobacterium smegmatis / Q000187:drug effects; D009169:Mycobacterium tuberculosis / Q000187:drug effects; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology*; D012293:Rifampin / Q000494:pharmacology*
chemical_list: D000995:Antitubercular Agents; D010455:Peptides; D012293:Rifampin
keywords: Antimicrobial peptides; Drug resistance; Mycobacterium tuberculosis; Synergy; α-Helical