Paradoxical effect of synthetic hydroxy isothiocyanates on antimicrobial action of aminoglycosides.

Hydroxy isothiocyanates, especially 2-(4-hydroxyphenyl)ethyl isothiocyanate (hITC), were examined for antimicrobial synergism with streptomycin (SM) against Escherichia coli. On the course of those experiments, a peculiar suppression of SM by a low concentration of hITC was observed, besides the antibacterial synergism of hITC with SM. Further, bactericidal activity of SM in physiological saline was reduced by addition of hITC. Time course experiments proved that the antagonistic effect of hITC occurred in an early stage after exposure of bacterial cells to SM.