Received: 30 March 2016 | Accepted: 25 October 2016 DOI 10.1002/jobm.201600175 RESEARCH PAPER Crataeva nurvala nanoparticles inhibit virulence factors and biofilm formation in clinical isolates of Pseudomonas aeruginosa Syed Ghazanfar Ali 1 | Mohammad Azam Ansari 1,2 | Haris M. Khan 1 | Mohammad Jalal 1 | Abbas Ali Mahdi 3 | Swaranjit Singh Cameotra 4 1 Department of Microbiology, Nanotechnology and Antimicrobial Drug Resistance Research Laboratory, Jawaharlal Nehru Medical College and Hospital, Aligarh Muslim University, Aligarh, Uttar Pradesh, India 2 Department of Medical Laboratories, College of Applied Medical Science, Buraydah Colleges, Buraydah, Saudi Arabia 3 Department of Biochemistry, King George Medical University, Lucknow, Uttar Pradesh, India 4 Institute of Microbial Technology (IMTECH- CSIR), Chandigarh, India Correspondence Syed Ghazanfar Ali, Department of Microbiology, Nanotechnology and Antimicrobial Drug Resistance Research Laboratory, Jawaharlal Nehru Medical College and Hospital, Aligarh Muslim University, Aligarh. 202002, Uttar Pradesh, India. Email: syedmicro72@gmail.com Green synthesized nanoparticles have gained great attention due to their non-toxic and non-hazardous nature. In the present study, bark extract of the medicinal plant in Ayurveda Crataeva nurvala (Buch–Ham) (CN) was chosen for the biosynthesis of silver nanoparticles (AgNPs). These NPs were characterized by Ultra violet visible spectroscopy, Fourier Transform Infra Red, Atomic Force Microscopy, and Transmission Electron Microscopy (TEM). The average particle size of green synthesized CN-AgNPs was 15.2 ± 1.01 nm. Gas chromatography- mass spectrom- etry analysis of methanolic bark extract involved in the formation of CN-AgNPs revealed lupeol as a major active component. In this study, CN-AgNPs (15 μg ml −1 ) efficiently suppressed the production of quorum sensing mediated virulence factors viz. pyocyanin, protease, hemolysin, and biofilm formation in Pseudomonas aeruginosa. The pyocyanin production was strongly inhibited (74.64%) followed by proteolysis (47.3%) and hemolysin production (47.7%). However, the biofilm forming ability was maximally reduced up to 79.70%. Moreover, the Confocal Laser Scanning Microscopic Analysis showed that CN-AgNPs inhibit colonization of P. aeruginosa on to the surface. Furthermore, TEM analysis revealed internalization of CN-AgNPs inside the bacterial cell. It is concluded that green synthesized AgNPs have great potential to inhibit virulence factors and biofilm forming ability of drug- resistant clinical isolates of P. aeruginosa. KEYWORDS Crataeva nurvala, P. aeruginosa, pyocyanin, quorum sensing, silver nanoparticles 1 | INTRODUCTION The emergence of multiple drug resistance in pathogenic microorganisms has become a serious threat worldwide, and this trend has aroused due to excessive use of antibiotics. Pseudomonas aeruginosa is a gram-negative opportunistic pathogen and attacks individuals suffering from cystic fibrosis, cancer, AIDS, or patients with indwelling medical devices or burns [1–4] P. aeruginosa produces various kinds of infections Abbreviations: AFM, atomic force microscope; AgNPs, silver nano- particles; CLSM, confocal laser scanning microscope; CN-AgNPs, Crataeva nurvala silver nanoparticles; ConA-FITC, concanavalin A-fluorescein isothiocyanate; FTIR, Fourier transform infra red; GCMS, gas chromatography Mass spectrophotometer; MIC, minimum inhibitory concentration; TEM, transmission electron microscope; UV Vis, ultra- violet visible spectroscopy. Syed Ghazanfar Ali and Mohammad Azam Ansari contributed equally to this work. J Basic Microbiol 2016; 9999: 1–11 © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim | 1 www.jbm-journal.com