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Inhibition of Helicobacter pylori urease activity by Origanum vulgare extract. Proteomics and genomics analysisD. Aguilar Lucero 1 , G. Salinas Ibáñez 1 , E. Callegari 2 , A. Arismendi Sosa 1 , F. Ferramola 1 , A. Correa 3 , T. Alarcón 3, 4 , A. E. Vega 11 Department of Microbiology. Universidad Nacional de San Luis, Avda Ejercito de los Andes 950 Cp: 5700 San Luis, Argentina.2 South Dakota-BRIN Proteomics Core Facility, SSOM, University of South Dakota, Vermillion, SD 57059, USA.3 Department of Microbiology. Hospital Universitario La Princesa. Instituto de Investigacion Princesa, Diego de León 26 28006 Madrid, Spain.4 Department of Preventive Medicine, Public Health and Microbiology. Medical School, Autonoumus University of Madrid, Spain.Herbal medicine has been used worldwide and is now recognized by World Health Organization (WHO) as an essentials building block for primary healthcare. Spices are considered as rich source of bioactive antimicrobial compounds. In this sense, Origanum vulgare belongs to the family Lamiaceae; it is an aromatic herb used as flavoring agent in both traditional and modern foods. The aerial part of the plant has high medicinal value and it is widely used for a variety of illnesses such as diarrhea, rheumatism, asthma as well as urinary tract disorders. Several studies show that Origanum vulgare L. essential oil possesses strong antimicrobial activity against pathogenic bacteria.Helicobacter pylori colonize the human stomach early in life and half of the people worldwide are carriers of this microorganism. Pathology such as gastritis, peptic ulcer, or gastric adenocarcinoma may be developed depending of virulence of the strain and the genetic characteristics of the host. Urease is one virulence factor that contributes in dissimilar ways to gastric mucosal damage and is required for the colonization and survival of H. pylori in the human stomach. Eradication treatments have been developed; however, the success of these treatments is compromised by the development of antimicrobial resistance due to natural selective pressure, indiscriminate use or the ability of microorganisms to grow in biofilms.Previously, we demonstrated the antimicrobial activity of aqueous extract of origanum (AEO) against H. pylori strain in planktonic and biofilm state, through the prevention of the formation of biofilms as well as the disruptions of the established H. pylori biofilms in vitro.The aim of this study was to investigate the effects of O. vulgare extract on urease activity of H. pylori at molecular level using proteomics and genomics analysis.In this study the strain HP146128 was treated with sub-inhibitory concentrations of oregano extract (1 mg/ml), and incubated for 26h. The proteomics analysis for the proteins extracted from H. pylori treated with and without a sub-inhibitory concentration of AEO, was performed using SDS-PAGE, followed by nano-Liquid Chromatography coupled to tandem mass spectrometry (nano-LC MS/MS) using a Quadrupole Time of Flight mass spectrometer (Q-Tof). The MS spectra were converted into a list of masses and submitted against an NCBInr database using a taxonomy filter for H. pylori through the program Mascot (www.matrixescience.com) with local license. The protein relative abundance was calculated from the label ?free? through spectral count approach. The gene expressions were determined using RT-PCR using 16S RNA as housekeeping gene.The results obtained showed that AEO down-regulates around 1,25 fold lower the ureA gene expression in both planktonic and biofilm cells. Moreover, the relative expression was corroborated by the proteomics analysis, showing for urease a down-regulation between 1.62 to 2.16 fold (log2 of the ratio).Urease inhibitors may be effective therapies for the treatment of diseases caused by H. pylori. However, the commercially available urease inhibitors are toxic and of low stability. So, the search for novel urease inhibitors is both scientifically and clinically important. The differential expression of urease at a molecular level using proteomic and genomic analysis observed in this study confirms the antibacterial effects of AEO against bacterial cells and provides a valuable insight into the mechanisms by which growth and pathogenicity in H. pylori could be inhibited. The use of AEO can contribute as alternative and complementary medicines, safe and less costly in the treatment of H. pylori infections.Keywords: Helicobacter pylori; Origanum vulgare; urease inhibitor;, genomics; proteomics.