[Mechanisms of adhesion of Staphylococci to biomaterials: effect of fusidic acid].

The production of slime, adherence to plastics and hydrophobicity are factors which regulate the colonisation of biomaterials by Staphylococci. The influence of fusidic acid on these 3 factors was studied by using 3 pairs of pathogenic strains of S. aureus and S. epidermidis. Each pair presented differences in the expression of one or several of these factors. The influence of fusidic acid was initially studied by determining the expression of these factors by these strains cultured in the presence of 0.03 mg/l and 0.5 mg/l of antibiotic. Hydrophobicity was measured by the Bath-test method, slime was detected by Trypan blue staining after fixation with Carnoy's fixative and adherence was determined on polystyrene. The variations observed were generally minor, except for S. epidermidis, high slime produces, which showed a reduced production. Using this collection of strains, we then selected mutants resistant to 2 micrograms/ml of fusidic acid. This resistance induced a reduction in the 3 colonisation factors and it can be proposed that strains resistant to fusidic acid have a lesser capacity to colonise than sensitive strains. The bacteria adhere to and colonise the majority of surfaces proposed to them [3, 7, 10]. This was the case for biomaterials used in medicine, whose number and diversity (catheters, prostheses) are continually increasing. Apart from thrombosis, the major complication is the development of infection. Coagulase positive or negative Staphylococci are very frequently responsible for this type of infection.(ABSTRACT TRUNCATED AT 250 WORDS)