Secondary Rays from Lipiodol and Bismuth Subnitrate Paste on Staphylococcus aureus and Bacillus coli communis.

Abstract

Attempts have been made to inhibit the growth of microorganisms by using secondary rays. These secondary rays are emitted from metals when they are exposed to x-ray. It has been shown that the higher the atomic weight of a metal, the greater is the bactericidal power of the secondary ray. 1 , 2 , 3 Many substances have been used with varying clinical success by different investigators.^4-10 Holthusen 11 has pointed out that there are many difficulties in the clinical application of secondary rays. The amount of the substance acting as radiators must be relatively large and still nontoxic. The action of secondary rays is limited, since they are so easily absorbed.

Experiments were conducted with Lipiodol and Beck's paste as the radiators. These substances are non-toxic, contain a metal of high atomic weight (33% Bismuth subnitrate in Beck's paste and 40% metallic iodine in Lipiodol) and have been previously used for their therapeutic value in certain clinical conditions. 4 , ^13-17 Staphylococcus aureus and Bacillus coli communis were used as the test bacteria.

The bacteria were grown on agar slants for 18 to 24 hours and emulsions were made containing approximately 3,000,000 and 1,200,000,000 organisms per cc. Of the first emulsion 0.2 cc. was pipetted on to a dry sterile agar plate which had been incubated for 48 hours, of the second emulsion 0.1 cc. was used. With a glass spatula the emulsion was spread evenly over the surface of the plate. These plates were dried in the incubator for 10 minutes before exposure to the x-ray. The inoculated agar plate was turned up side down and the substance acting as radiator was placed 1 mm. below the surface of the agar growth. The x-rays, therefore, first entered the bottom of the glass dish, next penetrated the agar, then the surface culture and finally struck the substance which was being investigated. 11 , 12 , 18 The secondary rays from the latter were reflected on to the surface of the growth and either caused inhibition of the growth or none at all. Ten erythema doses of x-ray were given in 30 minutes with the following factors: Transformer machine, 200 K. V., 4 M. A., 30 cm. focal distance. No filter. The plates were then incubated at 37° and the results read 20 hours later.