Lacticaseibacillus paracasei is a promising contender for fighting multi-drug-resistant/extensively-drug-resistant Enterobacteriaceae and Pseudomonas in foods

Document Type : Original Article

Authors

Department of microbiology, faculty of agriculture, Cairo university

Abstract

Background
Multi-drug-resistant/extensively-drug-resistant (MDR/XDR) Enterobacteriaceae and other Gram-negative bacteria are among the most important contemporary crises that menace mankind. Their spread into ready-to-eat (RTE) foods is a serious challenge to disease control and is associated with increased morbidity, mortality, and costs to society. It is vital to create non-antibiotic techniques to reduce/mitigate the risk of these microorganisms.
Objective
The current study was planned to search for the good candidate(s) biologically active lactic acid bacterial strain(s) to combat MDR/XDR Gram-negative bacteria derived from ready-to-eat foods.
Materials and methods
This study was attentive to the isolation of MDR/XDR Enterobacteriaceae and other Gram-negative bacteria in various RTE foods. Proteomic, molecular identification, and phylogenetic analysis were carried out on MDR/XDR isolates and biologically active LAB strains; antibiotic resistance profile of MDR Enterobacteriaceae and Pseudomonas were bent on. Minimum inhibitory (MIP) and bactericidal percentages (MBP) of the 4 supreme Lacticaseibacillus paracasei’cell-free supernatants (CFSs) were determined against selected MDR/XDR Enterobacteriaceae and Pseudomonas.  The effects of catalase, pH neutralization, and heat treatment on CFSs' antibacterial activity, and their mode of action using transmission electron microscopy (TEM) were investigated.
Results and conclusion
MDR Enterobacteriaceae were recovered from all cheese and vegetarian salads, 20 and 33.33% of sausages and luncheon samples on violet red bile glucose agar buttressed with ampicillin, penicillin, and erythromycin, in the presence or absence of tetracycline at 20 μl ml-1. Matching to 16S rRNA sequence analysis, the MALDI-TOF MS method successfully identified 48 of 53 Enterobacteriaceae isolates to the species level.  More than 94% of 75 isolated strains were XDR, with MAR indices of up to 0.91; 13.33% were extended-spectrum β-lactamase producers. Of the 67 putative lactic acid bacteria isolates, 23 had inconsistent inhibitory potency; among them, only four isolates were good candidates identified as Lacticasibacillus paracasei, their cell-free supernatants (CFSs) were effective against all MDR/XDR Enterobacteriaceae and Pseudomonas strains with inhibition zones up to 25.00 mm; the CFSs sustained most of their antibacterial activity after treatment with catalase or heating but lost at pH 7. MIP and MBP ranged from 2 to 7% and 3 to 30%, respectively; TEM validated their bactericidal action.

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