Antimicrobial activity of N-chloramine compounds

Cellular mechanisms of action of two representative N-chloramines were studied. Both compounds, 3-chloro-4,4-dimethyl-2-oxazolidinone (I) and N-chlorosuccinimide (III), inhibited bacterial growth and exerted profound inhibition of bacterial DNA, RNA, and protein synthesis at a concentration of 10(-5) M. Enzymes containing sulfhydryl groups generally were significantly inhibited by these chloramines at 10(-4) M. Dihydrofolate reductase, which contains no sulfhydryl groups, also was inhibited but at much higher chloramine concentrations (10(-2) M); ribonuclease, which also contains no sulfhydryl groups, was unaffected. All of these inhibitory effects of the chloramines could be prevented if sulfhydryl-containing reagents (mercaptoethanol or dithiothreitol) were added before or together with the chloramine. Once inhibition was produced by the chloramine, it was not reversible by later addition of the sulfhydryl reagents. These results suggest that these chloramines act at sulfhydryl sites as well as at other sites in both cells and purified enzymes.