A novel cyclic dipeptide from Lactiplantibacillus plantarum MC39 inhibits proliferation of multidrug-resistant Klebsiella pneumoniae W8 and Enterobacter hormaechei U25

Abstract

The present study pays special attention to lactic acid bacteria products, cyclic dipeptides (CDPs), as an effective prevention strategy that can be used to eradicate the threats posed by multidrug-resistant (MDR) Enterobacteriaceae. Herein, Lactiplantibacillus plantarum MC39, a strain isolated from an artisanal Egyptian cheese, was a producer of a novel CDP that could strongly inhibit, in vitro, MDR Klebsiella pneumoniae W8 and Enterobacter hormaechei U25, for the first time. Following partial purification with 80% ammonium sulphate precipitation and Sephadex G-100 chromatography, this biomolecule was identified as the cyclic dipeptide cyclo(Ala–Glu) using IR, HNMR, and LC–MS. Cyclo(Ala–Glu) was thermostable up to 121 °C, insensitive to pepsin and α-chymotrypsin, tolerant to organic solvents, active at acidic pH, and stable for 45 days of storage. Thus, it shows clear evidence to be usable as a bio-preservative in dairy products and as a potential therapeutic agent, controlling MDR K. pneumoniae and E. hormaechei.