Bacterial biofilm

Biofilms are a structured community of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface. Biofilm production allows bacteria to resist to antibiotic therapy, ensures infection persistence and the resistance to host immunity. Resistance to antimicrobial agents (e.g. antibiotics) of bacteria within biofilm seems to be related to several factors: a) increased difficulty of the antibiotic to penetrate through the extracellular matrix, b) a decrease in rate of cell division (β-lactam antibiotics are effective against Gram-positive bacteria in active multiplication), c) the presence of resistant phenotypes in a bacterial population genetically heterogeneous, d) greater resistance to phagocytosis. Staph. aureus represents a major agent of contagious bovine mastitis and its ability to form biofilm suggests that it is a possible important virulence factor in the establishment of staphylococcal infection. First study about vaccination against whole bacterial cells surrounded by their own biofilm matrix containing PNAG conferred protection against Staph. aureus infection and mastitis in a challenge study in sheep. The protection level was related to the features of the immunizing strain.