ADHESION OF STAPHYLOCOCCUS TO BIOMATERIAL S - INFLUENCE OF FUSIDIC ACID

The production of slime, adherence to plastics and hydrophobicity are factors which regulate the colonisation of biomaterials by Staphvlococ ci. The influence of fusidic acid on these 3 factors was studied by us ing 3 pairs of pathogenic strains of S. aureus and S. epidermidis. Eac h pair presented differences in the expression of one or several of th ese factors. The influence of fusidic acid was initially studied by de termining 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 blu e staining after fixation with Carnov's fixative and adherence was det ermined on polystvrene. 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 mutant s resistant to 2 mug/ml of fusidic acid. This resistance induced a red uction in the 3 colonisation factors and it can be proposed that strai ns resistant to fusidic acid have a lesser capacity to colonise than s ensitive strains. The bacteria adhere to and colonise the majority of surfaces proposed to them [3, 7, 10]. This was the case for biomateria ls used in medicine, whose number and diversity (catheters, prostheses ) are continually increasing. Apart from thrombosis, the major complic ation is the development of infection. Coagulase positive or negative Staphvlococci are very frequently responsible for this type of infecti on. Two processes play a kev role in the colonisation and development of infection by Staphylococci : firstly, adhesion of the bacteria to t he surface of the biomaterial, followed by production of slime, amorph ous mucoid substance, essentially composed of polysaccharides, which p rotects the bacteria from the host's defences and from the action of a ntibiotics [1, 2, 8, 18]. Antibiotics can act on these two processes a nd limit the bacterial colonisation [4]. Fusidic acid is an antibiotic which inhibits the synthesis of proteins [9] and, at subinhibitory an d inhibitory concentrations, it may be able to modify the bacterial su rface and adherence of Staphylococci as well as the production of slim e. The objective of this study was to assess the influence of fusidic acid on the hydrophobicity of strains of S. aureus and S. epidermidis, their adherence to polystyrene and their production of slime. As it i s possible to select in vitro strains resistant to fusidic acid, the a uthors also investigated whether such resistance induced a modificatio n in these colonisation factors.