Abstract

Pseudomonas aeruginosa causes infections in humans, particularly immune-compromised patients with cystic fibrosis, severe burns, and HIV, resulting in high morbidity and mortality. The pathogenic bacteria, P. aeruginosa, produces virulence factors regulated by the mechanism called quorum sensing system. The aim of this study was to assess the anti-quorum sensing activity of Ageratum conyzoides extracts. Chloroform fraction from hydro-methanolic extract at the sub-inhibitory concentration of 100 µg/mL reduced quorum sensing virulence factors production such as pyocyanin, elastases, and rhamnolipids in P. aeruginosa PAO1 after 8 and 18 h monitoring. Moreover, a significant inhibition in HSL-mediated violacein production on C. violaceum CV026 was recorded after 24 and 48 h monitoring without affecting the bacterial growth. The chloroform fraction was rich in polyphenols and triterpenes, and was found to interact with QS receptors. The regulatory genes (rhlR and lasR) and downstream genes [EC3] (RhlA and lasB) were the most affected, while synthase genes (lasI and rhlI) were the least affected. High-performance liquid chromatography with diode-array detection (HPLC-DAD) analysis allowed the identification and quantification of some compounds such as gallic acid, vanillic acid, ellagic acid, sinapic acid, and quercetin. Caffeic acid, rutin, and kaempferol were detected in trace amounts. The presence of these phytochemicals could be responsible for the observed anti-quorum activity. The present study is probably the first attempt to investigate the anti-QS potential of A. conyzoides against P. aeruginosa. These data provide additional scientific evidence to justify the wide use of A. conyzoides in traditional medicine in Burkina Faso.

Key words: Ageratum conyzoides, Chromobacterium violaceum, Pseudomonas aeruginosa, quorum sensing.