Modulation of quorum sensing-controlled virulence factors by Nymphaea tetragona (water lily) extract.
BACKGROUND
Nymphaea tetragona is a widely distributed ornamental species with ethnomedicinal uses in the treatment of diarrhea, dysentery, eruptive fevers, and infections. The anti-infectious activities of this herb have already been assessed to clarify its traditional use as a medicine.


OBJECTIVE
In this study, we aimed to verify the inhibitory effects of N. tetragona 50% methanol extract (NTME) on quorum sensing (QS)-controlled virulence factors of bacteria since QS and its virulence factors are novel targets for antimicrobial therapy.


METHODS
The antibacterial activity of this extract was evaluated against Chromobacterium violaceum and Pseudomonas aeruginosa. The inhibition of the violacein pigment of C. violaceum by NTME was determined qualitative and quantitative using standard methods. The effects of NTME on swarming motility, biofilm viability, pyocyanin production, and LasA protease activity were evaluated using P. aeruginosa. Finally, the in vitro and in vivo cytotoxicity of NTME were verified by MTT assay and oral administration to rats, respectively.


RESULTS
The extract had concentration-dependent antibacterial activity against gram-negative bacteria. NTME at 1/2× minimum inhibitory concentration (MIC), 1× MIC and 2× MIC significantly lowered the levels of violacein of C. violaceum compared to that of the control. The swarming motility of P. aeruginosa was inhibited by ≥70% by treatment with 1/2× MIC of NTME. There were remarkable reductions in pyocyanin production and LasA protease activity in the overnight culture supernatant of P. aeruginosa supplemented with NTME when compared with that of the untreated control. The confocal micrographs of 24h biofilms of P. aeruginosa exposed to NTME exhibited a lower number of live cells than the control. No toxic effect was observed in in vitro and in vivo cytotoxicity assays of NTME.


CONCLUSIONS
NTME was demonstrated to have significant concentration-dependent inhibitory effects on quorum sensing-mediated virulence factors of bacteria with non-toxic properties, and could thus be a prospective quorum sensing inhibitor.
College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, South Korea. Electronic address: mdakil_hossain@yahoo.com.
Md Akil
MA
Hossain
College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, South Korea. Electronic address: lovevet79@hanmail.net.
Seung-Jin
SJ
Lee
College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, South Korea; Institute of Clean Bio, Daejeon 301-212, South Korea. Electronic address: wismom@naver.com.
Ji-Yong
JY
Park
Faculty of Animal Science and Veterinary Medicine, Patuakhali Science and Technology University (Outer Campus), Babugonj, Barisal 8210, Bangladesh. Electronic address: vetphy_bgvc03@yahoo.com.
Md Ahsanur
MA
Reza
College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, South Korea. Electronic address: thkim56@knu.ac.kr.
Tae-Hwan
TH
Kim
College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, South Korea. Electronic address: leekj@knu.ac.kr.
Ki-Ja
KJ
Lee
Center for Nutraceutical and Pharmaceutical Materials, Division of Bioscience and Bioinformatics, Science campus, Myongji University, San 38-2, Namdong, Cheoin-Gu, Yongin, Gyeonggi 449-728, South Korea. Electronic address: jwsuh@mju.ac.kr.
Joo-Won
JW
Suh
College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, South Korea. Electronic address: parksch@knu.ac.kr.
Seung-Chun
SC
Park
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000472:pathogenicity*; D018441:Biofilms / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002861:Chromobacterium / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D051379:Mice; D008826:Microbial Sensitivity Tests; D030721:Nymphaea / Q000737:chemistry*; D010936:Plant Extracts / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D011710:Pyocyanine / Q000096:biosynthesis; D053038:Quorum Sensing / Q000187:drug effects*; D051381:Rats; D013211:Staphylococcus aureus / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D037521:Virulence Factors
D000900:Anti-Bacterial Agents; D010936:Plant Extracts; D013778:Tetrazolium Salts; D013844:Thiazoles; D037521:Virulence Factors; D011710:Pyocyanine; C022616:thiazolyl blue
Biofilm; Nymphaea tetragona; Pseudomonas aeruginosa; Quorum sensing inhibition; Virulence factors; Water lily