Influence of Color Filters on Photodynamic Action of Fluorescent Dyes on Gonococcus

Abstract

In the study of photodynamic action, Tappeiner 1 found that with eosin the green rays were more lethal to paramecium than the other parts of the spectrum. Later, Eidinow 2 demonstrated, however, that with the same dye the orange and yellow rays were more effective than the others. Hertel 3 in a more careful study showed that rays with different wave-lengths had different degrees of killing effect on the eosin-sensitized B. coli and paramecium. Most of the studies were made only with protozoa and B. coli, so it was thought of interest to apply similar tests to a pathogenic bacterium. In this study we have chosen gonococcus for experiment and in addition to eosin a few of the other dyes were also employed.

Different dilutions of eosin, methylene blue, trypaflavine, mercurochrome, protargol, argyrol, dimethyl-paraphenylenediamine hydrochloride, and tetramethyl-paraphenylenediamine hydrochloride were made with doubly distilled water, in 10-fold dilutions from 1:10 2 to 1:10¹⁰. The method of exposure to the ordinary light is the same as previously described. 4 However, in the experiment with filtered light the cells of the hollow-ground slides were covered with, instead of the ordinary thin cover-slips, different color-filters made by the Eastman Kodak Co. The filters wed were : red (F. NO. 29), orange (G. No. 15), yellow (K-1 No. 6), green (B. NO. 58), light blue (H. No. 45), blue (C. No. 49), and violet (D. No. 35). At intervals of 5, 10, 15, 30, 60 and 120 minutes after exposure, samples from both exposed and unexposed specimens were plated and examined for growth after 24 hours'incubation. The results of the photodynamic action of eosin, methylene blue, trypaflavine, and mercurochrome at dilutions from 1:10⁵ to 1:10⁹ after 60 minutes'exposure both to filtered and unfiltered lights are presented in Table I while those of the other dyes are omitted since it was found that their germicidal properties were not enhanced by the action of light.