Probiotic and Safety Properties Screening of Enterococcus faecalis from Healthy Chinese Infants
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Probiotic and Safety Properties Screening of Enterococcus faecalis from Healthy Chinese Infants Juan Wang 1 & Rong Da 2 & Xiaohong Tuo 1 & Yue Cheng 1 & Jie Wei 1 & Kaichong Jiang 1 & Jia Lv 1 & Omolade Monisayo Adediji 1 & Bei Han 1
# Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract The aim of this study was to evaluate the probiotic characteristics and safety of seven Enterococcus faecalis isolates from fecal samples of healthy Chinese infants. We evaluated the isolates’ tolerance to low pH, survival in bile salts and NaCl, adhesion ability, biofilm formation, antimicrobial activity, toxin gene distribution, hemolysis, gelatinase activity, antibiotic resistance, and virulence to Galleria mellonella. All strains survived at pH 5.0, in 7.0% NaCl, and in 3% bile salt. Adhesion to Caco-2 cells was above 10%. Strain A3-1 had higher adhesion ability toward mucin, collagen, and BSA in vitro, better antibacterial activity, and the strongest biofilm production. We detected seven virulence genes with a distribution of asa1 (100%), cylA (71.4%), esp (85.7%), hyl (14.3%), gelE (85.7%), ace (42.9%), and agg (71.4%). Although all strains were γ-hemolytic, none showed gelatinase activity based on physiological activity detection. All isolates were susceptible to benzylpenicillin, ampicillin, ciprofloxacin, levofloxacin, moxifloxacin, tigecycline, nitrofurantoin, linezolid, and vancomycin; they were not susceptible to erythromycin, quinupristin/dalofopine, and clindamycin. The virulence test of G. mellonella showed that, except for strains 106-1 and 113-1, the other strains had toxicity lower than 10%. Strain A3-1 may have the greatest potential to be developed as a probiotic. Keywords Enterococcus faecalis . Isolates . Stress tolerance . Probiotic characters . Safety evaluation
Introduction Enterococci are Gram-positive, normal flora of human and animal gastrointestinal tracts. They belong to the class of facultative anaerobic lactic acid bacteria (LAB). Enterococci are distributed widely and can be isolated from the environment, food, and human and animal gastrointestinal tracts [1, 2]. Enterococci have probiotic properties, such as high resistance to acids and bile salts [3–5], improving immunity [2], antioxidant and free radical scavenging activity [5], intestinal adhesion and localization [6, 7], enhancing apoptosis of human Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12602-019-09625-7) contains supplementary material, which is available to authorized users. * Bei Han [email protected] 1
School of Public Health, Xi’an Jiaotong University Health Science Center, P.O.44, NO.76 Yanta West Road, Xi’an 710061, Shaanxi, China
2
Department of Clinical Laboratory, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
cancer cells [8], antibacterial activity [8, 9], and regulating inflammation [10]. Because of these special properties, enterococci are used in supplementation of animal feed to prevent disease, relieve animal d
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