# Antibacterial and anti-virulence effects of Saxifraga stolonifera Meeb extracts against Pseudomonas aeruginosa

## TL;DR

This study shows that an extract from Saxifraga stolonifera can reduce the harmful effects of Pseudomonas aeruginosa by inhibiting its virulence and biofilm formation.

## Contribution

The n-butyl alcohol extract of Saxifraga stolonifera is shown to have anti-virulence effects against Pseudomonas aeruginosa.

## Key findings

- The n-butyl alcohol extract significantly downregulated virulence-related genes in P. aeruginosa.
- The extract inhibited biofilm formation and pyocyanin production at sub-inhibitory concentrations.
- HPLC-Q-TOF-MS/MS analysis identified over 11 compounds in the n-butyl alcohol extract.

## Abstract

Saxifraga stolonifera Meeb is widely used as a traditional Chinese medicine for the treatment of infections. This study aims to evaluate the antibacterial properties and suppression of virulence by Saxifraga stolonifera Meeb extracts on Pseudomonas aeruginosa. Following extraction of Saxifraga stolonifera Meeb with petroleum ether, ethyl acetate, n-butyl alcohol, and water, the n-butyl alcohol extract had the strongest activity against P. aeruginosa PAO1 and P. aeruginosa ATCC27853, with minimum inhibitory concentration (MIC) values of 10 and 5 mg/mL, respectively. In the presence of the n-butyl alcohol (n-BuOH) extract at 1/4MIC, genes lasI, lasR, rhlI, phzA1, phzA2, and pilG were decreased to levels ranging from 13% (lasI) to 43% (phzA2). Both biofilm formation and pyocyanin production of PAO1 were inhibited by the n-BuOH extract at sub-inhibitory concentrations. N-butyl alcohol extract analyzed by HPLC-Q-TOF-MS/MS showed more than 11 compounds. Overall, our results suggest that the n-BuOH extract from Saxifraga stolonifera Meeb may be used as a new anti-virulence agent for P. aeruginosa infection.

Pseudomonas aeruginosa infections pose severe challenges to clinical treatment, and anti-virulence therapy has emerged as a novel therapeutic strategy. This study demonstrates that the n-butanol extract of Saxifraga stolonifera exerts anti-virulence effects by downregulating virulence-related genes, inhibiting quorum-sensing systems, and biofilm formation. Moreover, its multiple bioactive components also possess antibacterial and anti-virulence properties. S. stolonifera is thus promising to be developed into a novel anti-virulence inhibitor against P. aeruginosa for the prevention and treatment of clinically relevant infections.