In-Vitro Characterization of Growth Inhibition against the Gut Pathogen of Potentially Probiotic Lactic Acid Bacteria Strains Isolated from Fermented Products.

Hye Kyeong Kang,Hyun Mi Jin,Sang-Soo Han,Myung Hoo Kim,Mi Hwa Lee,Ji Young Jung,Z-Hun Kim

doi:10.3390/microorganisms9102141

Abstract

Lactic acid bacteria (LAB) are probiotic candidates that may restore the balance of microbiota populations in intestinal microbial ecosystems by controlling pathogens and thereby promoting host health. The goal of this study was to isolate potential probiotic LAB strains and characterize their antimicrobial abilities against pathogens in intestinal microbiota. Among 54 LAB strains isolated from fermented products, five LAB strains (NSMJ15, NSMJ16, NSMJ23, NSMJ42, and NFFJ04) were selected as potential probiotic candidates based on in vitro assays of acid and bile salt tolerance, cell surface hydrophobicity, adhesion to the intestinal epithelium, and antagonistic activity. Phylogenetic analysis based on 16S rRNA genes showed that they have high similarities of 99.58–100% to Lacticaseibacillus paracasei strains NSMJ15 and NFFJ04, Lentilactobacillus parabuchneri NSMJ16, Levilactobacillus brevis NSMJ23, and Schleiferilactobacillus harbinensis NSMJ42. To characterize their antimicrobial abilities against pathogens in intestinal microbiota, the impact of cell-free supernatant (CFS) treatment in 10% (v/v) fecal suspensions prepared using pooled cattle feces was investigated using in vitro batch cultures. Bacterial community analysis using rRNA amplicon sequencing for control and CFS-treated fecal samples at 8 and 16 h incubation showed the compositional change after CFS treatment for all five LAB strains. The changed compositions were similar among them, but there were few variable increases or decreases in some bacterial groups. Interestingly, as major genera that could exhibit pathogenicity and antibiotic resistance, the members of Bacillus, Escherichia, Leclercia, Morganella, and Vagococcus were decreased at 16 h in all CFS-treated samples. Species-level classification suggested that the five LAB strains are antagonistic to gut pathogens. This study showed the probiotic potential of the five selected LAB strains; in particular, their antimicrobial properties against pathogens present in the intestinal microbiota. These strains would therefore seem to play an important role in modulating the intestinal microbiome of the host.

Highlights

The relationship between intestinal microbiota and host health is being increasingly recognized
Among a total of 54 bacterial strains isolated from fermented products, the acidtolerance ability (94.44 ± 4.27%) of NSMJ56 was much higher than LGG (71.60 ± 7.75%)
Through in vitro batch-culture of fecal microbiomes and 16S rRNA amplicon sequencing, we found that the genera containing pathogenic bacteria species (Morganella, Leclercia, Bacillus, Escherichia, Vagococcus, and Vibrio) were reduced in all five cell-free supernatant (CFS)-treated samples (Figures 2, 3, and S6)

Summary

Introduction

The relationship between intestinal microbiota and host health is being increasingly recognized. It is well established that a healthy intestinal microbiota plays a role in the digestion of nutrients, energy metabolism, protection of bacterial disease, and the development of a proper immune system conducing to host health [1,2,3]. Controlling pathogenic microorganisms in the intestinal microbial ecosystem is important for maintaining health for humans and animals. Probiotics are being used widely as one of the key solutions to restore the balance of the gut microbial ecosystem by controlling pathogens and promoting beneficial functions of the gut, resulting in the amelioration or prevention of intestinal or systemic disease phenotypes [12,13,14]

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