Abstract
Pseudomonas aeruginosa, an important opportunistic pathogen, is capable of producing various virulence factors and forming biofilm that are regulated by quorum sensing (QS). It is known that targeting virulence factor production and biofilm formation instead of exerting selective pressure on growth such as conventional antibiotics can reduce multidrug resistance in bacteria. Therefore, many quorum-sensing inhibitors (QSIs) have been developed to prevent or treat this bacterial infection. In this study, wogonin, as an active ingredient from Agrimonia pilosa, was found to be able to inhibit QS system of P. aeruginosa PAO1. Wogonin downregulated the expression of QS-related genes and reduced the production of many virulence factors, such as elastase, pyocyanin, and proteolytic enzyme. In addition, wogonin decreased the extracellular polysaccharide synthesis and inhibited twitching, swimming, and swarming motilities and biofilm formation. The attenuation of pathogenicity in P. aeruginosa PAO1 by wogonin application was further validated in vivo by cabbage infection and fruit fly and nematode survival experiments. Further molecular docking analysis, pathogenicity examination of various QS-related mutants, and PQS signal molecule detection revealed that wogonin could interfere with PQS signal molecular synthesis by affecting pqsA and pqsR. Taken together, the results indicated that wogonin might be used as an anti-QS candidate drug to attenuate the infection caused by P. aeruginosa.
Highlights
It has been known that the mass use of antibiotics increases bacterial resistance [1] and the development of new drugs has obviously slowed down, leading to a decrease in the cure rate and an increase in the mortality rate for bacterial infectious diseases
The results showed that the extracts of A. pilosa with deionized water or 70% ethanol both inhibited the most quorum sensing (QS)-related genes (Table 1) but did not impact the growth of P. aeruginosa PAO1 (Figure 1A)
Sd the QS system regulates most of the virulence factors and pathogenicity [7,23], we further examined the effects of the extracts from A. pilosa on the virulence phenotypes of PAO1.The virulencerelated phenotypes, including motility, elastase and pyocyanin production, and biofilm formation, were reduced when different concentrations of the 70% ethanol extracts of A. pilosa were used (Figure 1B)
Summary
It has been known that the mass use of antibiotics increases bacterial resistance [1] and the development of new drugs has obviously slowed down, leading to a decrease in the cure rate and an increase in the mortality rate for bacterial infectious diseases. Novel therapy strategies have been urgently needed for bacterial infection treatment, especially for the antibiotic-resistance pathogens. Pseudomonas aeruginosa, a Gram-negative opportunistic pathogen, is frequently found in the department of respiratory and critical care medicine and can cause acute and chronic infections in immunocompromised or burned patients. P. aeruginosa synthesizes adhesion substances such as extracellular polysaccharides for adherence, secretes protease to destroy the structure of host cells for entrance, and produces some virulence factors such as pyocyanin to defend itself against the immune system of host [2]. P. aeruginosa often forms a biofilm, which relates to extracellular polysaccharide and bacterial motility [3]. Biofilm formation is capable of increasing bacterial drug resistance hundreds of times [4]
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