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

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

doi:10.3389/fmicb.2020.566473

Abstract

Staphylococcus aureus 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 Lactobacillus strains with significant inhibitory effect on the translocation of S. aureus 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 S. aureus by well diffusion assay. Subsequently, two strains preincubated with Caco-2 monolayers were found to inhibit the translocation of S. aureus CMCC26003 by 80.95 and 43.96%, respectively, via the transcellular translocation assay. These two strains were then identified to be Lactobacillus fermentum NCU3087 and L. fermentum 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 S. aureus, to different extent. Moreover, two Lactobacillus 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 Lactobacillus strains with significant inhibitory effect on the translocation of S. aureus, and their safeness for application was evaluated, thereby providing potential solutions for prevention of S. aureus and prophylaxis of related diseases.

Highlights

Staphylococcus aureus is a common commensal of human skins and mucosal membranes (Argudín et al, 2010)
Overuse of antibiotics makes the drugs much less effective at treating infections among patients presenting to emergency departments, which is becoming a global risk especially in China, where doctors prescribe antibiotics to half of all outpatients, far above recommended levels, according to the World Health Organization (WHO)
Thereafter, the inhibitory effect of NCU3087 and NCU3088 on the translocation of S. aureus in the Caco-2 cell monolayer model was determined via the transcellular translocation assay

Summary

Introduction

Staphylococcus aureus is a common commensal of human skins and mucosal membranes (Argudín et al, 2010). As 30–50% humans are S. aureus carriers, food handlers carrying this bacterium on the hands or in the noses are regarded as the main source of food contamination (Loir et al, 2009). Consumption of foods contaminated with sufficient amounts of preformed enterotoxin can lead to staphylococcal food poisoning. S. aureus is a leading cause of gastroenteritis (Hennekinne et al, 2012). S. aureus has long been notorious for its pathogenicity and refractory, while there is no effective vaccine. Alternative strategies are urgently needed for the prevention of S. aureus

Methods

Results

Conclusion