P0323 Poster Session I New therapeutic alternatives ANTIMICROBIAL ACTIVITY AND PROTEOME ANALYSES OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS TREATED WITH VIOLACEIN B. Araujo Lima1, M. Brocchi1 1Genética Evolução e Bioagentes, UNICAMP, Campinas, Brazil Violacein ([3-(1,2-dihydro-5-(5-hydroxy-1H-indol-3-yl)-2-oxo-3H-pyrrol-3-ilydene)-1,3-dihydro-2H-indol-2- one]) is a purple pigment produced by environmental bacterial species such as Pseudoalteromonas luteociolacea, Janthinobacterium lividum, Duganella spp and by Chromobacterium violaceum. This indole-derivative is synthesized from the condensation of two L-tryptophan molecules. Violacein synthesis is known to be induced under aerobic conditions and in response to quorum sensing, although the exact role in the physiology of producing microorganisms is still unknown. This compound has shown to have several biological properties including including antibacterial, antifungal, antiviral, antiprotozoal and antitumor activity. As antibiotic, violacein has significant activity against Bacillus subtilis, Pseudomonas aeruginosa e Staphylococcus aureus. Objectives. The aim of this work is to investigate the antibiotic activity of violacein commercially produced against several species of gram-positive and gram-negative bacteria (medical strains). The staphylococcal time-response growth curves and the proteomic overview. Methods. The bacterial strains were assayed regarding the minimal inhibitory concentrations (MIC), the minimum bactericidal concentration (MBC) as suggested by the CLSI. To quantify the effect of violacein on the Staphylococcus aureus N315 growth (MRSA strain), a time-response growth curve in vitro was obtained in the presence of violacein and determining changes in protein expression using two dimensional protein electrophoresis. Results: Violacein exhibited antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), microorganisms that are often related to hospital-acquired infections. MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) values of violacein produced commercially were 0.625 µM and 1.25 µM respectively, and analysis of growth and time-kill curves showed an antibacterial effect against MRSA for 12 hours. Proteome analyses revealed that violacein at 1.25 µM concentration affect the expression of several major functional classes of whole cells proteins in MRSA, including biological processes in cell wall biosynthesis and cell division. The FtsZ and MurA proteins emerged as potential targets of violacein in S. aureus. Conclusion. The violacein produced commercially demonstrated antimicrobial activity against S. aureus MRSA and the effects on the metabolism of S. aureus have been described, indicating possible targets and pathways affected by this drug. These data indicate violacein as a potential drug for the treatment of infections caused by MRSA..