Virulence properties of a peptide hemolysin produced by Enterococcus faecalis

M. T. Furumura, P. M. S. Figueirêdo, G. V. Carbonell, A. L. Darini, Maria Rosa Quaresma Bomfim, Rosimary de Jesus Gomes Turri, Francyelle Costa Moraes, Cristina Monteiro de Andrade, Hermínio Benitez Rabello Mendes, Valério Monteiro Neto, T. Yano

Department Clinical, Toxicologicals and Bromatologicals Analisys, USP, Ribeir?o Preto, Brazil.
Department of Microbiology and Immunology, Biological Institute, Universidade Estadual de Campinas, Campinas, Brazil.
Medical Biology, Adolfo Lutz Institut, Campinas, Brazil.
Research Group of Endemic and Parasitic Diseases, CEUMA University, S?o Luis, Brazil.

DOI: 10.4236/abb.2012.37112                

Abstract

The characterization and prevalence of virulence factors associated with enterococcal invasiveness and severity of disease are important areas to be investigated. Recently, we described the production of a heat-stable hemolysin by clinical isolates of Enterococcus faecalis cultived in BHI-GA (BHI with glucose and L-arginine). Now, we purified the hemolysin from the culture supernatant by ultra-filtration (PM-10 membrane) and ethanol extraction followed by chromatography in a mBondapak C18 and Superdex Peptide columns. The hemolytic activity was not affected by the proteolytic enzymes. Cholesterol, phospholipids, EDTA and also bivalent ions did not inhibit the hemolytic activity. Among the various carbohydrates, only dextran 4 protected the erythrocytes against lyse. Scanning electron microscopy showed that lyse of erythrocytes occured at once after the exposure to the hemolysin. The mito-chondrial activity and the cell membrane integrity were significantly affected by the hemolysis, within 20 min of exposure and caused apoptosis after 12 h incubation, 51.92% in HeLa and 68% in HEp-2 cells, analyzed by flow cytometry. These results suggest that the heat-stable pore forming hemolysin might be a putative virulence factor in enterococci infections.

Keywords

Enterococcus Faecalis; Cytotoxin, Heat-Stable Hemolysin; Human Epithelial Cells; Apoptosis

Conflicts of Interest

The authors declare no conflicts of interest.

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