Antimycobacterial activity of the plectasin derivative NZ2114.

INTRODUCTION

Mycobacteria have a unique hydrophobic membrane with several lipid-enriched layers that are low in permeability, setting them apart from other bacteria. This complex structure, consisting of three distinct layers is crucial for cell growth, virulence, and providing a barrier to antibiotics. Previously, we identified a plectasin variant, NZX, which showed activity against in several murine tuberculosis (TB) infection studies. In this study, we investigated another plectasin variant, NZ2114, known for its effectiveness against Gram-positive bacteria, as a potential antimycobacterial peptide both and .

METHODS

The resazurin microtiter assay (REMA) was used to determine MIC; a time-kill assay was performed to evaluate long-term effects; scanning electron microscopy (SEM) was employed to visualize peptide impact; a checkerboard assay assessed drug compatibility; MTT and WST-8 assays were used to estimate peptide toxicity; intracellular killing was evaluated using primary macrophages; peptide stability was assessed in human serum; and a murine tuberculosis (TB) infection model was used to verify the peptide's efficacy.

RESULTS

NZ2114 effectively killed mycobacteria at a minimal inhibitory concentration (MIC) of 6.1 µM, was non-toxic to primary human cells, and remained resistant to serum degradation while preserving its antimycobacterial capacity. In a checkerboard assay, NZ2114 demonstrated synergy with the first-line TB drugs isoniazid and ethambutol. The antimicrobial effect was also observed against several clinical isolates of Gram-positive bacteria, including , and Methicillin-Resistant (MRSA). In our murine TB infection model, compared to untreated controls, NZ2114 eliminated with a log reduction of 0.72 (81.14%) after three doses.

DISCUSSION

These studies suggest NZ2114 as a potential TB therapy, aiding in the control of this significant infectious disease.