Effect of Salicylate on Antibacterial Activity of Different Antibiotics

Susceptibility of Psudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis to gentimicin and ceforaxime was affected by salicylaye. In presence of salicylaye (15 mM) and gentamicin (1.0 .mu.g/ml), log efficiency of plating (log E. O. P. s) for the tested bacteria were -1.24, -2.17 and -1.66 respectively. The activity of cefotaxime against Bacillus subtilis was reduced (log E. O. P. = 1.33). The highest potentiating effects of salicylaye were shown when using gentamicin against Staphylococcus aureus, cefotaxime against Ps. aeruginosa, log E. O. P.s were -3.0, and -2.4 respectively. On the other hand, no significant effects were detected with cefotaxime against Staphylococcus aureus (log E. O. P. = -0.04). No significant killing was shown in presence of gentamicin or salicylaye alone. There was no significant effect for salicylaye on MICs (By broth dilution) could be observed except in case of gentamicin against Staphyloccus aureus, which was reduced from 0.02 .mu.g/ml to 0.0012 .mu.g/ml. These results raise the concern that high concentrations of salicylaye in patients might interfere with antibiotic therapies.