# The Antimicrobial Peptide C14R Is Active Against All Pathogenic Species of the ESKAPE Group

## TL;DR

A new antimicrobial peptide called C14R effectively kills all six ESKAPE pathogens, which are known for causing drug-resistant infections.

## Contribution

C14R shows potent activity against all six ESKAPE pathogens, including multidrug-resistant strains.

## Key findings

- C14R has MICs ranging from 3.4 µg/mL to 45.2 µg/mL against ESKAPE pathogens.
- C14R inhibits biofilm formation in Gram-positive pathogens like MRSA and VRE.
- Gram-negative biofilms are more tolerant to C14R compared to Gram-positive ones.

## Abstract

The global rise in antimicrobial resistance among the ESKAPE pathogens represents a major challenge to public health. Here, we report the broad-spectrum antibacterial activity of the synthetic antimicrobial and pore-forming peptide C14R against all six ESKAPE species. Using a radial diffusion assay and resazurin-based viability testing, C14R exhibited a potent bactericidal effect with minimum inhibitory concentrations (MICs), defined as the lowest concentration of an antimicrobial agent that completely inhibits visible growth of planktonic microorganisms, ranging from 3.4 µg/mL (Enterococcus faecium, vancomycin-resistant) to 45.2 µg/mL (Klebsiella quasipneumoniae, ESBL). C14R also inhibited biofilm formation by Gram-positive pathogens, with minimum biofilm inhibitory concentrations (MBICs), referring to the minimal concentration required to prevent the development of biofilms, of 15.0 µg/mL (Staphylococcus aureus, MRSA) and 22.0 µg/mL (E. faecium, VRE), whereas Gram-negative biofilms showed higher tolerance. Together, these findings demonstrate that C14R retains high activity against multidrug-resistant ESKAPE strains, highlighting its potential as a lead compound for the development of next-generation antimicrobial drugs to expand the portfolio of available antibiotics and brace health systems against emerging severe infections.