Baicalin Inhibits Biofilm Formation and the Quorum-Sensing System by Regulating the MsrA Drug Efflux Pump in Staphylococcus saprophyticus

Abstract

Staphylococcus saprophyticus (S. saprophyticus) is one of the main pathogens that cause serious infection due to its acquisition of antibiotic resistance. The efflux pump decreases antibiotic abundance, and biofilm compromises the penetration of antibiotics. It has been reported that baicalin is a potential agent to inhibit efflux pumps, biofilm formation, and quorum-sensing systems. The purpose of this study was to investigate whether baicalin can inhibit S. saprophyticus biofilm formation and the quorum-sensing system by inhibiting the MsrA efflux pump. First, the mechanism of baicalin inhibiting efflux was investigated by the ethidium bromide (EtBr) efflux assay, measurement of ATP content, and pyruvate kinase (PK) activities. These results revealed that baicalin significantly reduced the efflux of EtBr, the ATP content, and the activity of PK. Moreover, its role in biofilm formation and the agr system was studied by crystal violet staining, confocal laser scanning microscopy, scanning electron microscopy, and realtime polymerase chain reaction. These results showed that baicalin decreased biofilm formation, inhibited bacterial aggregation, and downregulated mRNA transcription levels of the quorum-sensing system regulators agrA, agrC, RNAIII, and sarA. Correlation analysis indicated that there was a strong positive correlation between the efflux pump and biofilm formation and the agr system. We demonstrate for the first time that baicalin inhibits biofilm formation and the agr quorum-sensing system by inhibiting the efflux pump in S. saprophyticus. Therefore, baicalin is a potential therapeutic agent for S. saprophyticus biofilm-associated infections.

Efflux pump inhibitory activity of biologically synthesized silver nanoparticles against multidrug‐resistant Acinetobacter baumannii clinical isolates

“…A lot of of approaches have been reported for inhibiting the efflux pump activity including the downregulation of efflux pump genes [42]. Wang et al [43] investigated the MsrA efflux pump inhibitory effect of Baicalin on Staphylococcus saprophyticus . The results showed that Baicalin significantly reduced the efflux of EtBr and downregulated the mRNA transcription level of MsrA gene.…”

Bisdemethoxycurcumin Reduces Methicillin-Resistant Staphylococcus aureus Expression of Virulence-Related Exoproteins and Inhibits the Biofilm Formation

“…A qRT-PCR was carried out according to the methods previously described [35]. Briefly, ATCC 33591 was cultured in MHB overnight and treated with sub-inhibitory concentrations of BDMC for 4 h. The sample without BDMC was taken as a control.…”

Induction of Antibacterial Metabolites by Co-Cultivation of Two Red-Sea-Sponge-Associated Actinomycetes Micromonospora sp. UR56 and Actinokinespora sp. EG49

“…On the other hand, PK is known to be a critical enzyme in catalyzing the final step of glycolysis, which involves the transfer of a phosphoryl group from phosphoenolpyruvate to ADP, producing pyruvate and ATP [32]. Recently, it was identified as a "superhub", listed among the top 1% of all interacting proteins in S. aureus and found to be a key regulator of the quorum-sensing system and the biofilm formation process in staphylococci [33][34][35]. Considering these points together with the structural similarity of our compounds (1-3) to previously well-known topoisomerase inhibitors, we selected Staphylococcus DNA gyrase-B and PK as possible molecular targets to mediate the observed antibacterial and antibiofilm activities of the induced phenazine derivatives toward S. aureus.…”