SURFACOME CHANGES of METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS IN BACTERIAL GROWTH UNDERGOING USNIC TREATMENT BY PROTEOMIC APPROACH

Introduction and Objectives: bacteria surfacome contains proteins from all membrane compartments exhibiting pivotal role in host colonization. Methicillin-resistant Staphylococcus Aureus (MRSA), a gram + bacteria resistant to a large variety of antibiotics is considered one of the emerging pathogens in pulmonary failure in cystic fibrosis (CF)(1). Nowadays, treatment for lung infections is focusing on the use a novel biomolecule, usnic acid with antimicrobial activity, arising from Lichens as Secondary Metabolite (SML) (2). In our previous investigation regarding antibacterial action of SMLs against MRSA in CF patients, we demonstrated that usnic acid is active at subinhibitory concentration (MIC), lower than other hepatotoxic SLMs (3). No data literature for proteomic, key to understanding the molecular mechanism that drives multiple effects of usnic acid on virulence and chemo resistance of MRSA have been published. So the aim of the present work is to analyze surfacome changes in membrane fraction from usnic acid-treated MRSA. Methods: we performed a comparative proteomic analysis between membrane protein fractions from untreated (CTRL) and usnic acid-treated (USNIC) samples using 2-DE combined with MALDI-TOF MS/MS experiment. For each condition all samples were electrophoretically run three times as 3 technical and 2 biological replicates. Results and Discussion: 23 differentially expressed proteins were uniquely MS-identified. Noteworthy was the usnic acid treatment which induced the synthesis of 2 isoforms of Acyl-CoA esterase family protein which is involved in the synthesis of fatty acids within the bacterial cell wall biogenesis, ensuring survival and virulence for MRSA. Conclusions: The discovery of the enzymes Acyl-CoA esterase could represent a milestone for the development of novel and efficient antibacterial drugs. References (1) De Vrankriijker AM. et al, Pediatr. Respir. Rev. 2010;11:246-254 (2) Francolini I. et al, Antimicrob. Agents Chemother. 2004; 48(11):4360-4365 (3) Pompilio A. et al, J. Future Microbiology 2013; 8(2):281-292