Quercetin impairs Streptococcus pneumoniae biofilm formation by inhibiting sortase A activity

Abstract

Biofilm formation mediated by sortase A (srtA) is important for bacterial colonisation and resistance to antibiotics. Thus, the inhibitor of SrtA may represent a promising agent for bacterial infection. The structure of Streptococcus pneumoniae D39 srtA has been characterised by crystallisation. Site‐directed mutagenesis was used for the determination of the key residues for the activity of S. pneumoniae D39 srtA. An effective srtA inhibitor, quercetin, and its mechanism was further identified using srtA activity inhibition assay and molecular modelling. In this study, the crystal structure of S. pneumoniae D39 srtA has been solved and shown to contain a unique domain B. Additionally, its transpeptidase activity was evaluated in vitro. Based on the structure, we identified Cys207 as the catalytic residue, with His141 and Arg215 serving as binding sites for the peptide substrate. We found that quercetin can specifically compete with the natural substrate, leading to a significant decrease in the catalytic activity of this enzyme. In cells co‐cultured with this small molecule inhibitor, NanA cannot anchor to the cell wall effectively, and biofilm formation and biomass decrease significantly. Interestingly, when we supplemented cultures with sialic acid, a crucial signal for pneumococcal coloniation and the invasion of the host in the co‐culture system, biofilm loss did not occur. This result indicates that quercetin inhibits biofilm formation by affecting sialic acid production. In conclusion, the inhibition of pneumococcal srtA by the small molecule quercetin offers a novel strategy for pneumococcal preventative therapy.

Defeating Antibiotic-Resistant Bacteria: Exploring Alternative Therapies for a Post-Antibiotic Era

“…Therefore, it is worth investigating whether combine SPR741 with carbapenem can be used for the treatment of porindeficient carbapenem-resistant bacteria infection. [39,40] The structure of compounds were adopted from PubChem database (https://pubchem.ncbi.nlm.nih.gov/).…”

“…Anti-E. coli quorum sensing system [39,40] The structure of compounds were adopted from PubChem database (https://pubchem.ncbi.nlm.nih.gov/).…”

“…Reduces attachment of S. aureus to fibronectin-coated or fibrinogen-coated surface; inhibits biofilm formation of S. pneumoniae [39,40] The structure of compounds were adopted from PubChem database (https://pubchem.ncbi.nlm.nih.gov/).…”

“…Moreover, wild-type S. aureus Newman treated with QEN showed a significant reduce for the attachment of bacteria to fibronectin-coated or fibrinogen-coated surfaces [39]. QEN also displays the ability to inhibit the biofilm formation of Streptococcus pneumoniae by affecting sialic production [40]. However, the in vivo anti-virulence activity of QEN is still unknown.…”

Otitis media pathogens – A life entrapped in biofilm communities

“…For instance, bacterial autolysin LytA and the and phage lysozymes Cpl-1 and Cpl-7 reduced around 80%, 70% and 55%, respectively (Domenech et al 2011). Other proposed alternative or adjuvant antimicrobial therapies to fight pneumococcal biofilms include xylitol (Kurola et al 2011), HAMLET (a natural complex from human milk) (Laura R. , plant extracts or essential oils (Yadav et al 2013;Talekar et al 2014;Minami et al 2017), ceragenins (Moscoso et al 2014), nitric oxide (Allan et al Allan et al 2017), zinc oxide nanoparticles (Bhattacharyya et al 2018), flavonoids (Wang et al 2018), and even human amniotic/chorionic membrane extracts (Yadav et al 2017), among others.…”