Effects of<i>Bacillus</i>Serine Proteases on the Bacterial Biofilms

Abstract

<i>Serratia marcescens</i> is an emerging opportunistic pathogen responsible for many hospital-acquired infections including catheter-associated bacteremia and urinary tract and respiratory tract infections. Biofilm formation is one of the mechanisms employed by <i>S. marcescens</i> to increase its virulence and pathogenicity. Here, we have investigated the main steps of the biofilm formation by <i>S. marcescens</i> SR 41-8000. It was found that the biofilm growth is stimulated by the nutrient-rich environment. The time-course experiments showed that <i>S. marcescens</i> cells adhere to the surface of the catheter and start to produce extracellular polymeric substances (EPS) within the first 2 days of growth. After 7 days, <i>S. marcescens</i> biofilms maturate and consist of bacterial cells embedded in a self-produced matrix of hydrated EPS. In this study, the effect of <i>Bacillus pumilus</i> 3-19 proteolytic enzymes on the structure of 7-day-old <i>S. marcescens</i> biofilms was examined. Using quantitative methods and scanning electron microscopy for the detection of biofilm, we demonstrated a high efficacy of subtilisin-like protease and glutamyl endopeptidase in biofilm removal. Enzymatic treatment resulted in the degradation of the EPS components and significant eradication of the biofilms.