INHIBITION OF BACTERIAL ADHESION BY SUB-INHIBITORY CONCENTRATIONS - BRODIMOPRIM VS TRIMETHOPRIM

There is accumulating evidence that sub-inhibitory concentrations (sub -MICs) of many antibiotics are not without effect on bacteria and even though they do not kill bacteria, they are still able to interfere wi th some important aspects of bacterial cell function. The aim of the p resent study was to investigate the effect of sub-MICs of brodimoprim and trimethoprim on Escherichia coli and Staphylococcus aureus adhesiv eness to human mucosal cells. Sub-MICs of brodimoprim down to 1/32 MIC (0.03 mu g/ml) significantly reduced the E. coli adhesion to human bu ccal epithelial cells and this inhibition was significantly higher tha n the corresponding pattern for trimethoprim. Adhesion of S. aureus wa s significantly reduced down to 1/16 MIC for both brodimoprim and trim ethoprim but no significant differences resulted between the two patte rns. 2,4 Diaminopyrimidines and related structures have a high affinit y for the enzyme dihydrofolate reductase and this causes a reduction i n the synthesis of essential purines, thus reducing also DNA and the s ynthesis or expression of surface adhesins.