# Antibacterial Activity of Jelleine-I, a Peptide Isolated from Royal Jelly of Apis mellifera, Against Colistin-Resistant Klebsiella pneumoniae

## TL;DR

Jelleine-I, a peptide from royal jelly, shows strong antibacterial effects against colistin-resistant Klebsiella pneumoniae in lab and insect models.

## Contribution

Jelleine-I is shown to effectively kill colistin-resistant Klebsiella pneumoniae and reduce biofilm viability and mortality in infected larvae.

## Key findings

- Jelleine-I has a minimum inhibitory concentration (MIC) range of 16 to 128 µM against colistin-resistant Klebsiella pneumoniae.
- Jelleine-I at 200 µM kills all CRKP cells in 150 minutes and reduces biofilm biomass and viability.
- Treatment with Jelleine-I reduces mortality and improves health in Tenebrio molitor larvae infected with CRKP.

## Abstract

Klebsiella pneumoniae can acquire resistance mechanisms to colistin and present a pan-resistant phenotype. Therefore, new alternative agents are imperative to control this pathogen, and the peptide Jelleine-I stands out as a promising prototype. Here, the antibacterial activity of Jelleine-I against clinical isolates of colistin-resistant K. pneumoniae (CRKP) was investigated. Antimicrobial activity was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time kill-curve assay. The release of 260 nm-absorbing materials (DNA/RNA) and the release of proteins were used in the lysis assay. Anti-biofilm activity was studied in microplates. In vivo activity was determined by the lethality assay using Tenebrio molitor larvae. The results show that the MIC of Jelleine-I ranged from 16 to 128 µM and the MBC was on average 128 µM. Jelleine-I at 200 µM killed all CRKP cells in suspension (106 colony-forming units (CFU)/mL) after 150 min of incubation. Jelleine-I acts on the CRKP cell membrane inducing lysis. Biomass and viability of CRKP-induced biofilms are reduced after treatment with Jelleine-I, and the use of this peptide in T. molitor larvae infected with CRKP reduces lethality and improves overall larval health. In conclusion, Jelleine-I is a potential prototype for the development of new antimicrobial agents.