Further studies on the production of staphylococcus aureus toxin.

Abstract

In a previous paper 1 we showed that certain strains of Staphylococcus aureus produce an exotoxin which causes necrosis when injected intradermally into rabbits. With the methods used at that time only 8 out of 118 strains from pathogenic sources produced a toxin of sufficient strength to be demonstrable by this method. Recently, however, by two improvements in method, it has been possible to obtain the toxin from 13 out of 14 strains. These changes were: first, the growth of the staphylococcus culture in an atmosphere containing 10 per cent carbon dioxide and, second, the use of “Proteose peptone”∗ instead of Witte peptone in the broth media.

For cultivation in the presence of CO₂, the method of Cohen and Fleming 2 was used. The stronger toxin production in this atmosphere may be due to the fact that the pH of the broth cultures does not rise above 7.6 even after 8 days growth. When grown under the usual atmospheric conditions, even after 3 or 4 days growth, the staphylococcus cultures have a pH of 8 or over.

There appeared to be some variation in different strains, but a strong toxin was produced most regularly when “proteose peptone” was used.

In the production of other bacterial toxins it was found the amount produced by the staphylococcus varied greatly when different commercial brands of peptone were used in the medium.

The table is given to show the amount of toxin which seven different strains of staphylococcus aureus produced on media prepared in exactly the same way, except for the presence of 6 different peptones. All of the cultures were grown in the same jar with 10 per cent carbon dioxide at 37° for 3 days.