BIOFOULING, 2016 VOL. 32, NO. 2, 155–165 http://dx.doi.org/10.1080/08927014.2015.1133810 Study of the major essential oil compounds of Coriandrum sativum against Acinetobacter baumannii and the efect of linalool on adhesion, bioilms and quorum sensing Susana Alves a , Andreia Duarte a  , Sónia Sousa b and Fernanda C. Domingues a   a CICS-UBI – Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal; b Fiber Materials and Environmental Technologies Research Unit, University of Beira Interior, Covilhã, Portugal ABSTRACT Acinetobacter baumannii is a pathogen that has the ability to adhere to surfaces in the hospital environment and to form bioilms which are increasingly resistant to antimicrobial agents. The aim of this work was to study the antimicrobial activity of the major oil compounds of Coriandrum sativum against A. baumannii. The efect of linalool on planktonic cells and bioilms of A. baumannii on diferent surfaces, as well as its efect on adhesion and quorum sensing was evaluated. From all the compounds evaluated, linalool was the compound with the best antibacterial activity, with minimum inhibitory concentration values between 2 and 8 μl ml −1 . Linalool also inhibited bioilm formation and dispersed established bioilms of A. baumannii, changed the adhesion of A. baumannii to surfaces and interfered with the quorum- sensing system. Thus, linalool could be a promising antimicrobial agent for controlling planktonic cells and bioilms of A. baumannii. KEYWORDS Acinetobacter baumannii; essential oil of Coriandrum sativum; linalool; bioilm; adhesion; quorum sensing ARTICLE HISTORY Received 8 April 2015 Accepted 10 December 2015 Introduction Acinetobacter baumannii is an opportunist microor- ganism capable of causing nosocomial infections that are responsible for high mortality and morbidity rates, mainly in intensive care units (Tomaras et al. 2003; Camp & Tatum 2010; Wang et al. 2010). his pathogen is frequently reported as the cause of ventilator-associ- ated pneumonia, bacteremia, secondary meningitis, res- piratory and urinary tract infections, skin, wound, burn and blood stream infections, endocarditis, surgical site infections and septicemia (Tomaras et al. 2003; Hanlon 2005; Loehfelm et al. 2008; Camp & Tatum 2010). It is hypothesized that A. baumannii persists in medical environments, resists antimicrobials, and causes disease due to its ability to adhere to and to form bioilms on abiotic surfaces common in the hospital environment (McConnell et al. 2013). Bioilms are multicellular three-dimensional structures constituted of cells in close contact with other cells and incorporated in an extracel- lular matrix composed of carbohydrates, nucleic acids, proteins and other macromolecules (Tomaras et al. 2003; Coenye & Nelis 2010). he irst step in bacterial bioilm formation is the reversible primary attachment of cells to the surface, and ater the initial adhesion there is irreversible attachment, with the production of the exo- polysaccharides (EPS) necessary for bioilm maturation (Tomaras et al. 2003; Gaddy & Actis 2009; McConnell et al. 2013). It is also known that quorum sensing (QS), an autoinducer-receptor mechanism, plays a role in bioilm formation by Acinetobacter spp. (Bhargava et al. 2010). QS is a bacterial cell to cell communication mechanism and involves cell density-dependent signaling through acyl homoserine lactones (AHL) in Gram-negative bac- teria (Bhargava et al. 2010; Prashanth et al. 2012; Tay & Yew 2013). Concerning the control and treatment strategies for multidrug-resistant A. baumannii infec- tions, sulbactam has been successfully used; however, its activity is decreasing. Although polymyxins and min- ocycline showed reliable antimicrobial activity against A. baumannii isolates, their use caused great concern owing to their toxicity (Karageorgopoulos & Falagas 2008). herefore, with the increasing incidence of nosocomial infections caused by A. baumannii and the low eicacy of the available drugs and disinfectants, new © 2016 Taylor & Francis CONTACT Fernanda C. Domingues fdomingues@ubi.pt Downloaded by [b-on: Biblioteca do conhecimento online UL] at 09:38 27 January 2016