Viscoelastic properties of Staphylococcus aureus and Staphylococcus epidermidis mono-microbial biofilms

The viscoelastic properties of mono-microbial biofilms produced by ocular and reference staphylococcal strains were investigated. The microorganisms were characterized for their haemolytic activity and agr typing and the biofilms, grown on stainless steel surface under static conditions, were analysed by Confocal Laser Scanning Microscopy. Static and dynamic rheometric tests were carried out to determine the steady-flow viscosity and the elastic and viscous moduli. The analysed biofilms showed the typical time-dependent behaviour of viscoelastic materials with considerable elasticity and mechanical stability except for Staphylococcus aureus ATCC 29213 biofilm which showed a very fragile structure. In particular, S. aureus 6ME biofilm was more compact than other staphylococcal biofilms studied with a yield stress ranging between 2 and 3 Pa. The data obtained in this work could represent a starting point for developing new therapeutic strategies against biofilm-associated infections, such as improving the drug effect by associating an antimicrobial agent with a biofilm viscoelasticity modifier.