Quercetin Inhibits Biofilm Formation by Decreasing the Production of EPS and Altering the Composition of EPS in Staphylococcus epidermidis

Yongqi Mu,Hong Zeng,Wei Chen

doi:10.3389/fmicb.2021.631058

Abstract

Staphylococcus epidermidis is an opportunistic pathogen, and its biofilm formation ability is an important virulent factor. Quercetin, a typical flavonoid ubiquitously used in dietary supplementation, is known for its antioxidant property, but its anti-biofilm activity against S. epidermidis remains unknown. In this study, the anti-biofilm activity of quercetin was investigated using S. epidermidis ATCC35984, a strong biofilm-positive strain. An attempt was made to disclose the mechanisms of the anti-biofilm activity of quercetin. S. epidermidis exhibited a less cell surface hydrophobicity after quercetin treatment. Also, quercetin effectively inhibited S. epidermidis cells from adhering to the glass slides. Quercetin downregulated the intercellular adhesion (ica) locus and then polysaccharide intercellular adhesin (PIA) production was reduced. Therefore, S. epidermidis cells became less hydrophobic, which supported quercetin’s anti-biofilm effect. Our study suggests that quercetin from plants be given further attention as a potential anti-biofilm agent against the biofilm formation of S. epidermidis, even biofilm infections of other bacteria.

Highlights

Staphylococcus epidermidis is the most frequently encountered coagulase-negative Staphylococci (CoNS) species on human skin
The results showed that quercetin inhibited the biofilm formation of S. epidermidis ATCC 35984 in a dose-dependent manner (Figure 1A)
The results showed that the biofilms treated with 125 μg ml−1 of quercetin became thinner, looser, and even easier to eradicate than the untreated biofilms (Figure 1B)

Summary

Introduction

Staphylococcus epidermidis is the most frequently encountered coagulase-negative Staphylococci (CoNS) species on human skin. The diseases caused by S. epidermidis and other CoNS are chronic and re-occur, which contrasts the potential of S. aureus to cause acute infections (Lowy and Franklin, 1998). Epidemiological studies have demonstrated the presence of the genus Staphylococcus, Staphylococcus aureus, and S. epidermidis, in approximately 50% of cases of bovine mastitis (Mello et al, 2020). The consequences of mastitis include economic losses due to the costs of treatment, lower milk production, changes in product quality, and culling (Halasal et al, 2007). Mastitis is a public health hazard since it can cause zoonoses and food poisoning (Fernandes et al, 2011; Gomes et al, 2016). S. epidermidis is notorious in particular for causing infections on indwelling medical devices, including cardiac implantable electric device (CIED) infection (Okada et al, 2021) and orthopedic device-related infection (Thompson et al, 2020), in which the pathogenesis usually involves biofilm formation. The antibiotic therapy against pathogenic bacteria is currently decreasing, which is partly attributed to biofilm

Methods

Results

Conclusion