AUTHOR=Peng Zhen , Wei Benliang , Huang Tao , Liu Zhanggen , Guan Qianqian , Xie Mingyong , Li Haijuan , Xiong Tao 

TITLE=Screening, Safety Evaluation, and Mechanism of Two Lactobacillus fermentum Strains in Reducing the Translocation of Staphylococcus aureus in the Caco-2 Monolayer Model

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.566473

DOI=10.3389/fmicb.2020.566473

ISSN=1664-302X

ABSTRACT=<p><italic>Staphylococcus aureus</italic> is a common commensal of humans, and its translocation from gastrointestine to peripheral organs and tissues could cause severe diseases and complications. This study focuses on the screening and characterization of <italic>Lactobacillus</italic> strains with significant inhibitory effect on the translocation of <italic>S. aureus</italic> through Caco-2 monolayers. First, strains with strong affinity for mucin and Caco-2 cells were obtained, via microtiter plate assay and adhesion assay, respectively. Obtained bacteria were further tested for their inhibitory effects on the growth of <italic>S. aureus</italic> by well diffusion assay. Subsequently, two strains preincubated with Caco-2 monolayers were found to inhibit the translocation of <italic>S. aureus</italic> CMCC26003 by 80.95 and 43.96%, respectively, via the transcellular translocation assay. These two strains were then identified to be <italic>Lactobacillus fermentum</italic> NCU3087 and <italic>L. fermentum</italic> NCU3088. Second, the mechanism of inhibition was investigated by analyzing the relative concentration of tight junction proteins and proinflammatory cytokines of Caco-2 cells, by Western blot and enzyme-linked immunosorbent assay, respectively. Results showed that both NCU3087 and NCU3088 significantly attenuated the degradation of occludin, claudin-1, ZO-1, and JAM-1 and suppressed the secretion of interleukin 6 and tumor necrosis factor-α induced by <italic>S. aureus</italic>, to different extent. Moreover, two <italic>Lactobacillus</italic> strains could barely translocate the Caco-2 monolayers, had no hemolytic activity, displayed strong resistance to gastrointestinal fluids, and were sensitive or moderate sensitive to nine clinically relevant antibiotics. Collectively, this study identified two <italic>Lactobacillus</italic> strains with significant inhibitory effect on the translocation of <italic>S. aureus</italic>, and their safeness for application was evaluated, thereby providing potential solutions for prevention of <italic>S. aureus</italic> and prophylaxis of related diseases.</p>