Antibiotic-resistant bacteria have emerged from the widespread use of antibiotics worldwide and have prompted the search for new sources of antimicrobial substances. Pinus spp. contain several bioactive compounds consisting mainly of terpenes, terpenoids and some other aromatic and aliphatic constituents. These compounds exert important biological effects, and pine oils have found wide application in the industry. In the present study, we have evaluated the potential activity of the resin-oil of Pinus elliottii and its major compound dehydroabietic acid (DA) against multiresistant bacteria by MIC, minimum bactericidal concentration and time-kill assays. The MIC of the resin-oil of P. elliottii varied between 25 and 100 mg ml "1 . As for DA, the MIC and minimum bactericidal concentration varied between 6.25 and 50 and between 6.25 and 100 mg ml "1 , respectively. The time-kill assay conducted with DA at 6.25 mg ml "1 evidenced bactericidal activity against Staphylococcus epidermidis (American Type Culture Collection 14990) within 24 h. On the basis of these results, the resin-oil of P. elliottii and its major compound DA play an important part in the search for novel sources of agents that can act against multiresistant bacteria. INTRODUCTIONThe widespread use of antibiotics worldwide has culminated in a high prevalence of infections by antibioticresistant bacteria. Indeed, exchangeable genetic elements such as plasmids, transposons and integrons disseminate antibiotic resistance in many bacteria (Nikokar et al., 2013). The slower introduction of new chemotherapeutic drugs into the market and clinical practice over the last few years may yet be another reason for the growing number of resistant bacteria (Russell, 2002;Coelho et al., 2013). This slow-down may have caused a number of antibiotics to lose their efficacy against antibiotic-resistant organisms, making the use of drugs that are often reserved for last-line treatment necessary (Coelho et al., 2013). The overall result of the emergence of human pathogenic organisms exhibiting multidrug resistance has been the search for new antimicrobial substances from other sources, including plants (Ahmad & Beg, 2001).During the 1950s, exotic, fast-growing trees such as Pinus spp. were introduced in southern Brazil to supply wood for the paper industry and cellulose for energy production. Today, Brazil holds one of the largest planted areas in the world (Pacheco et al., 2009). A number of compounds displaying anti-inflammatory, antiparasitic, antioxidant, antimutagenic and antitumour activities, as well as the ability to regulate cancer-related proteins, have been isolated from different Pinus spp. (Tó ro et al., 2003;Karonen et al., 2004;Kwak et al., 2006;Li et al., 2007;Politeo et al., 2011). Some species are frequently used for their medicinal benefits, such as diuretic and expectorant actions, to treat diseases that include pulmonary, urinary, hepatic and hypertensive disorders (Lawless, 1992;Politeo et al., 2011). Moreover, pine oils are widely employed as fragran...

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