CORRELATION BETWEEN REDUCTION OF SURFACE HYDROPHOBICITY OF STAPHYLOCOCCUS-AUREUS AND THE DECREASE IN ITS ADHESIVENESS INDUCED BY SUBINHIBITORY CONCENTRATIONS OF BRODIMOPRIM

Hydrophobic interactions are involved in the mechanism of adhesion of a variety of bacteria to host tissues. Bacterial attachment to human c ells is modulated by a change in interfacial free energy and this is c orrelated with surface hydrophobicity of bacterial cells. In S. aureus (one ATCC25923+four clinical isolates) hydrophobicity before and afte r incubation with subinhibitory concentrations (sub-MICs) of brodimopr im (BMP), a dimethyoxypyrimidine recently entered clinical practice, w as measured by sessile drop technique as the contact angle. BMP is a n ew molecule derived from trimethoprim by substitution of the OCH3 grou p in position 4 of the benzyl-ring with a bromine atom, Bacterial adhe siveness of the same S. aureus strains was measured under the same exp erimental conditions, BMP significantly decreased the surface hydropho bicity of S. aureus strains at one-half MIC and one-quarter MIC. At su b-MICs concentrations BMP also reduced the adhesiveness to human epith elial buccal cells but this effect was significant down to one-sixteen th MIC. The two phenomena are correlated and hydrophobicity is involve d in bacterial adhesiveness but the molecular mechanisms for the two p henomena do not completely overlap, with adhesiveness the more complex and based on a system involving both the bacteria and the epithelial cells with their specific surface characteristics. (C) 1995 The Italia n Pharmacological Society