K-134. Adhesion, Biofilm Formation and Invasion Ability in Staphylococcus aureus and Listeria monocytogenes Are Impaired by the Action of a Bacterial Exoprotease

G. Scoarughi¹, C. Longhi¹, A. Cellini¹, R. Papa¹, A. Carpentieri², L. Seganti¹, P. Pucci², A. Amoresano², P. Cocconcelli³, S. Gazzola³, M. Artini¹, L. Selan¹;
¹Univ. of Rome La Sapienza, Rome, ITALY, ²Univ. of Naples Federico II, Naples, ITALY, ³Univ. Cattolica Piacenza, Piacenza, ITALY.

Background: Listeria monocytogenes is a facultative intracellular pathogen associated with severe food-borne diseases. Staphylococcus aureus exerts its virulence mainly by adhesion and toxin production. Both these Gram-positive bacteria possess the ability to invade eukaryotic cells by binding receptors with surface ligands and show the ability to adhere to abiotic and biotic surfaces such as food-processing surfaces (L. monocytogenes) or prosthetic devices (S. aureus). In this study we assess the E. coli recombinant form of serratiopeptidase (SPEP), a secreted protease produced by S. marcescens, on virulence related properties of L. monocytogenes and S. aureus. Methods: 3 L. monocytogenes strains and 3 S. aureus strains were used. Interference of SPEP on biofilm formation was assessed by crystal-violet staining and by SEM. SPEP interference on adhesion/invasion ability, was studied on human Caco-2 (L. monocytogenes) and HeLa cells (S. aureus). A proteomic study was designed to identify surface proteins affected by SPEP treatment. Proteins were fractionated by SDS-PAGE and autolytic patterns were assessed by zymographic analysis. Protein bands present in non-treated samples, whose intensity diminished following SPEP treatment, were analysed by MALDI/MS. Mass spectral data were used for protein identification. Results: All strains treated with SPEP showed complete inhibition or significant reduction of biofilm formation. SPEP treatment caused also a significant decrease of S. aureus adhesion and invasion of human cells, while in L. monocytogenes only the invasion ability was affected. Proteomic data showed that in both these pathogens SPEP treatment affects the expression of surface proteins related with adhesion/invasion, septation and bacterial metabolism. In S. aureus trascriptomic analysis confirmed proteomic data. Intracellular protein pattern analysis of SPEP-treated and untreated S. aureus is ongoing. Conclusions: SPEP treatment is effective to impair adhesion to abiotic surfaces for both bacteria. SPEP strongly reduces also biofilm maturation and invasion ability on eukaryotic cells of L. monocytogenes and S. aureus strains.

240/K. Bacterial Stress Responses - I

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