Short communication Nanotechnology improves the therapeutic efficacy of Melaleuca alternifolia essential oil in experimentally infected Rhamdia quelen with Pseudomonas aeruginosa Carine F. Souza a, ⁎, Matheus D. Baldissera b , Roberto C.V. Santos b , Renata P. Raffin c , Bernardo Baldisserotto a, ⁎ a Department of Physiology and Pharmacology, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil b Department of Microbiology and Parasitology, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil c Laboratory of Nanotechnology, Centro Universitário Franciscano, Santa Maria, RS, Brazil abstract article info Article history: Received 22 January 2017 Received in revised form 6 February 2017 Accepted 8 February 2017 Available online 09 February 2017 Pseudomonas aeruginosa is one of the most important agent representing high mortality and significant economic losses in aquaculture. Due to growing reports of antimicrobial resistance, it is important to develop studies in- volving alternative therapies and new technologies, including the use of essential oils and nanotechnology. In this sense, the aim of this study was to evaluate whether Melaleuca alternifolia essential oil (TTO) exerts in vivo bactericidal action against P. aeruginosa strain PA01, as well as to evaluate whether nanotechnology is able to im- prove this action in experimentally infected Rhamdia quelen. Our results demonstrated that free TTO and nanoencapsulated TTO exert potent bactericidal action against P. aeruginosa. The most important finding is that TTO nanoparticles possess 100% of curative efficacy, while free TTO possesses 70% of curative efficacy. In summary, the nanoencapsulation of TTO was able to improve the bactericidal action of TTO, and may be consid- ered an important approach to prevent and/or treat infected animals with P. aeruginosa. © 2017 Elsevier B.V. All rights reserved. Keywords: Nanotechnology Aquaculture diseases Fish pathogen TTO 1. Introduction Aquaculture is one of the fastest growing food producing sectors be- cause of augmentation demand for fish and seafood worldwide, since continuing expansion of aquaculture is viewed as a key strategy to en- sure global food and nutritional security (Ellis et al., 2016). In attempt to supply the global fish demand, animals are subjected to conditions of intensive production, that causes high-stress response and conse- quently increases the incidence of diseases, such as caused by Pseudo- monas aeruginosa, leading a decrease in productivity (Feckaninová et al., 2017). Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen belonging to Pseudomonadaceae family, which is widespread in nature, inhabiting soil, water, humans and animals, including fishes (Thomas et al., 2014). In the particular interest, P. aeruginosa is considered one of the most common bacterial pathogen in marine and freshwater aqua- culture, and is considered one of the causes of spoilage of aquatic prod- ucts (Gram and Huss, 1996). This disease is characterized by ulcerative syndrome, haemorrhagic septicemia, and tail, fin and gill rot (Thomas et al., 2014). Moreover, P. aeruginosa strain PA01 possesses the capability to colonize surfaces by forming biofilm, that are a conjunct of cells more resistant to antimicrobial agents (Comin et al., 2016). Moreover, the excessive use of antibiotics leads to negative impacts on human health and environment, such as resistance, accumulation of residuals in edible tissues and depression of immune system (Tu et al., 2008). In this sense, a recent study conducted by Peng et al. (2017) demonstrated the resistance of P. aeruginosa against ciprofloxacin, demonstrating the need to new alternative forms to treat this infection, such as the use of Melaleuca alternifolia (an Australian native plant) essential oil, popularly known as “tea tree oil” (TTO). Recently, a study conducted by Ambrosio et al. (2017) concluded that essential oils may be considered an important approach to treat bacterial diseases. The TTO demonstrated several antibacterial proper- ties against experimentally infected fish with Aeromonas hydrophila (Souza et al., 2016), as well as in vitro action against P. aeruginosa (Comin et al., 2016). In this sense, our hypothesis is that TTO can exert in vivo effects in experimentally infected fish. Moreover, a recent study conducted by Comin et al. (2016) demonstrated that nanoparti- cles containing TTO exerts potent antimicrobial activity against P. aeruginosa through inhibiting adhesion and motility, as well as potent antibiofilm activity. The use of nanotechnology has many advantages because allows the active principles to act on site of interest, increase the capacity to remain for long periods in bloodstream and protects the active principle against enzymatic hydrolyses (Nair et al., 2016). Thus, we believe that nanotechnology can enhance the bactericidal ac- tion against P. aeruginosa in vivo. Aquaculture 473 (2017) 169–171 ⁎ Corresponding authors. E-mail addresses: carinedefs@yahoo.com.br (C.F. Souza), bernardo@smail.ufsm.br (B. Baldisserotto). http://dx.doi.org/10.1016/j.aquaculture.2017.02.014 0044-8486/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture