Anti-virulence activities of some <em>Tillandsia</em> species (Bromeliaceae)

Background: Using molecules that inhibit bacterial virulence is a potential strategy to fight infections, with the advantage that, in contrast to bactericidal compounds, they do not induce resistance. Several compounds with anti-virulence properties have been identified in plants, however, they represent a small portion of the total diversity, and in Mexico there are still few studies on this matter.  Hypothesis: Extracts of species of the Tillandsia genus inhibit the expression of diverse virulence factors without affecting the bacterial growth.  Studied species: Tillandsia recurvata (L.) L., T. schiedeana Steud. and T. fasciculata Sw.  Study site and date: These species were collected in December 2016 in the municipalities of Ixtlahuaca and Santo Tomás de los Plátanos, State of Mexico. Methods: The ability of dichloromethane (CH2Cl2) and methanol (CH3OH) extracts to inhibit production of violacein in Chromobacterium violaceum was evaluated, as well as the virulence factors regulated by quorum sensing, motility and biofilm in Pseudomonas aeruginosa. In addition, the bioactive fractions obtained were partially identified by 1H NMR. Results: CH2Cl2 and CH3OH extracts reduced violacein production from 43 to 85 %, but only those from CH2Cl2 reduced protease activity, biofilm formation and swarming. Interestingly, CH3OH extracts stimulated the formation of biofilms by up to 37 %. Presence of terpenes and phenolic compounds in these species was confirmed. In T. schiedeana glycosylated compounds and cycloartane-type triterpenes were identified. Conclusion: The species of Tillandsia show anti-virulence activity, mainly on factors related to adhesion and dispersion in Pseudomonas aeruginosa.