Abstract
Lacticaseibacillus paracasei CNCM I-5369, formerly Lactobacillus paracasei CNCM I-5369, produces bacteriocins that are remarkably active against Gram-negative bacteria, among which is the Escherichia coli-carrying mcr-1 gene that is involved in resistance to colistin. These bacteriocins present in the culture supernatant of the producing strain were extracted and semi-purified. The fraction containing these active bacteriocins was designated as E20. Further, E20 was loaded onto alginate nanoparticles (Alg NPs), leading to a highly active nano-antibiotics formulation named hereafter Alg NPs/E20. The amount of E20 adsorbed on the alginate nanoparticles was 12 wt.%, according to high-performance liquid chromatography (HPLC) analysis. The minimal inhibitory concentration (MIC) values obtained with E20 ranged from 250 to 2000 μg/mL, whilst those recorded for Alg NPs/E20 were comprised between 2 and 4 μg/mL, which allowed them to gain up to 500-fold in the anti-E. coli activity. The damages caused by E20 and/or Alg NPs/E20 on the cytology of the target bacteria were characterized by transmission electron microscopy (TEM) imaging and the quantification of intracellular proteins released following treatment of the target bacteria with these antimicrobials. Thus, loading these bacteriocins on Alg NPs appeared to improve their activity, and the resulting nano-antibiotics stand as a promising drug delivery system.
Highlights
Antibiotic resistance and its rapid dissemination worldwide have become a major societal threat that must be taken into consideration in order to not jeopardize the progress of modern medicine in the fight against the infectious diseases
To improve the antibacterial activity registered against E. coli strains, the E20 fraction was loaded on alginate nanoparticles’ (Alg NPs) surface, leading to an Alg NPs/E20 nano-antibiotic formulation
Lacticaseibacillus paracasei CNCM I-5369 produces antagonistic substances which were isolated as a mixture: The E20 fraction
Summary
Antibiotic resistance and its rapid dissemination worldwide have become a major societal threat that must be taken into consideration in order to not jeopardize the progress of modern medicine in the fight against the infectious diseases. In the United States, another recent study outlined that 162,044 people die from multi-drug-resistant infections yearly in this country [3], which makes a huge difference regarding the 23,000 deaths occurring yearly and usually reported by the Center for Diseases Control and Prevention. Colistin has never been withdrawn from the veterinary circuit and has largely been used for the prevention and treatment of certain GNB infections, and even as a growth factor in poultry and pig farming sectors [6,7]. Since 2015, a transferable system of colistin resistance has been discovered in E. coli strains, of human and animal origin, isolated in China [8]. This study has revealed that colistin resistance was attributed to the mcr-1 plasmid gene encoding the synthesis of a phosphoethanolamine transferase [8]. We demonstrate that bacteriocins produced by Lacticaseibacillus paracasei CNCM I-5369, referred as the E20 fraction, are active against a panel of E. coli strains, and this activity is significantly enhanced through E20 adsorption on alginate nanoparticles (Alg NPs)
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