Interaction of bacteria isolated from clinical biofilms with cardiovascular prosthetic devices and eukaryotic cells

Purpose

To identify the relationships between some infectious agents implicated in cardiovascular diseases with the cellular substrate and prosthetic devices in the presence of antibiotics.

Specific objectives

Strains isolation and identification, comparative study of antibiotic resistance of planktonic (disk diffusion, E-test, automatic systems) and sessile (using original experimental models for in vitro development of monospecific biofilms) bacterial cells, virulence assays (adherence and invasion of HeLa cells, slime test, soluble virulence factors expression), dynamic study of biofilm development on inert substrata, under the influence of antibiotics, the influence of cellular and soluble bacterial fractions on HeLa cells (by flow cytometry and real-time PCR).

Results

The identified strains were isolated from different sources, the etiology being dominated by Gram-negative non-fermentative bacilli, Gram-positive cocci and yeasts, harboring invasion enzymes responsible for development of systemic infections. The isolated strains exhibited a high level of antibiotic resistance to beta-lactams, aminoglycosides and quinolones, and an evident tendency of colonizing the cellular and inert substrate, the degree of colonization depending on the physico-chemical nature of the substrate. By comparison with planktonic ones, the sessile bacterial strains expressed a changed profile of antibiotic resistance, this aspect being very important for the readjustment of the treatment and prevention of infections associated with prosthetic devices. In vitro experiments suggested that different fractions of S. aureus cultures could trigger the release of proinflammatory (TNF-α, IL-1b, IL-6) and anti-inflammatory (IL-8) cytokines and induced apoptosis in HeLa cells.