Graduate Thesis Or Dissertation
 

Some aspects of the mechanism of action of iodophor and other germicides on microorganisms

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  • The concentrations of iodophor necessary to reduce the activity of several metabolic enzyme systems 50 percent was used as the basic approach in attempts to elucidate the mechanism of germicidal action of iodine. For comparisons, a chlorine-releasing germicide (Trichlorocide) and a quaternary ammonium compound were also tested. It was found that on parts per million basis, Trichlorocide inhibited the activity of most of the enzymes 50 percent in smaller concentrations than either iodophor or the quaternary ammonium compound. However on a molar basis iodophor was the most effective in inhibiting the activity of a majority of the enzymes. Conversely, the activity of most enzymes was not inhibited by the quaternary ammonium compound. In all tests where there was at least 50 percent inhibition of enzyme activity, the concentration of the germicide was well below that normally used for disinfection and sanitation purposes, providing further evidence on the sensitive nature of certain enzyme systems to inactivation by small concentrations of germicide. Alcohol dehydrogenase and glucose-6-phosphate dehydrogenase when partially inactivated by iodophor were completely reactivated by glutathione and cysteine respectively. Likewise, cysteine was able to partially reverse iodophor inactivated lactic dehydrogenase. This evidence indicated that iodophor inactivated these enzymes, at least in part, through oxidation of their essential sulfhydryl groups. In addition, the activity of catalase was reduced 60 percent when the enzyme was exposed to 60 ppm iodophor under alkaline conditions indicating that the inactivation occurred as a result of iodination reactions. Only partial success was achieved in efforts to demonstrate the in vivo oxidation of yeast glucose-6-phosphate dehydrogenase sulfhydryl groups by iodophor. In comparing the effects of iodophor and Trichlorocide on glucose oxidation and viability of Saccharomyces cerevisiae cells, it was found that with an exposure time of 30 seconds at one and two ppm, iodophor inhibited both glucose oxidation and viable cell count to a greater extent than Trichlorocide. However when the exposure time was increased to five minutes, Trichlorocide was a more effective inhibitor. Cysteine and dithiothreitol were able to partially reverse the inhibitory effects of iodophor on glucose oxidation and completely restore viable cell counts. With both Pseudomonas fragi and Pseudomonas aeruginosa cells, as little as 0.75 ppm of iodophor was able to substantially reduce glucose oxidation and cell viability. Dithiothreitol was able to partially reverse these inhibitory effects. From these results it was concluded that the activity of iodophor on the organisms studied was due, at least in part, to the oxidation of sulfhydryl groups located on proteins and other constituents essential for glucose oxidation and maintenance of cell viability.
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