The formation of hydrogen peroxide by an obligatory anaerobe (Actinomyces necrophorus). The tolerance of this organism for peroxide.

When difficulty was experienced in obtaining growth of Actinomyces necrophorus after the culture had been allowed to come in contact with air (see previous paper), the work of McLeod and Gordon, of Callow, and of Avery and his associates, dealing with hydrogen peroxide production by bacteria immediately came to mind. Using the benzidine test with a bit of raw potato to supply the necessary oxidases, as suggested by Avery in his work on the Pneumococcus, the production of peroxide by this organism when in contact with air was readily demonstrated. After exposure to the air in a shallow layer, distinct positive tests for peroxide were obtained in from 1 1/2 to 2 hours in plain bouillon cultures which had been grown under petrolatum seal for 24 to 48 hours. The fluid part of cooked meat cultures, when fairly free from meat fragments, usually gave a positive reaction after two hours exposure but if a considerable quantity of meat fragments was present the reaction was delayed or prevented. When meat fragments were present, the reaction, if it occurred at all, could be obtained over only a short period of time. In most cases a reaction could not be obtained after 8 hours under such conditions, whereas in plain bouillon it could sometimes be obtained for as long as 24 hours.

The inhibiting effect of the meat fragments suggested the presence of catalase. It was also found that when titrated solutions of hydrogen peroxide were introduced into sterile meat medium, the peroxide rapidly was destroyed, or combined in some way so that it would not react to benzidine. The introduction of 1 cc. of a 3 per cent solution of hydrogen peroxide through a melted petrolatum seal and the rapid congealing of the seal formed a means of detecting small amounts of gas formation readily.