Toxicity of filtrates of B. Friedlander.

A number of investigators have made studies on filtrable toxic products produced by bacteria in young cultures. These products have been variously called soluble toxins, × substances and endotoxins. In order to produce constant effects it has been necessary to inject the filtrates intravenously into rabbits and mice. The use of a small laboratory animal and a method of inoculation which would allow a somewhat greater range in the materials introduced would aid in a more detailed study concerning the nature of these substances.

It was thought that an organism more highly virulent for the mouse than those used by other observers might produce a filtrate in young cultures which would be toxic intraperitoneally. A strain of B. Friedlander (non-lactose-fermenting) was chosen which consistently caused death in about 12 hours when introduced intraperitoneally into mice. This culture was grown for various periods in veal infusion Witte peptone broth with and without 0.1 per cent dextrose. Sterile filtrates of these cultures were used for injections.

Eighteen-hour cultures produced no effect on the mice. Older cultures, 42 hours, 66 hours, 5 days, 10 days, and 20 days, while more toxic, did not produce constant effects. In some cases mice receiving 1 cc. of the filtrate survived, while others receiving 0.5 cc. died in 8 to 24 hours.

Eighteen-hour cultures grown anaerobically, and aerobic cultures in Martin's media, produced no effect in the animals. The intraperitoneal injection of such substances as gum tragacanth, bile, and 1:500 calcium chloride, as peritoneal irritants, followed by the injection of a 42-hour filtrate likewise caused no reaction.

Rabbits inoculated intravenously with 3 cc. of the filtrate of this strain, grown in veal infusion Witte peptone broth, did not show any signs of discomfort with the 18-hour cultures.