Influence of Ketene on the Potency of Antipneumococcus Serum. ∗ †

Abstract

Recently we 1 showed that the treatment of anti-Brucella horse serum with ketene for 35 min or more prevents anaphylactic shock in animals sensitized to the original antiserum. Furthermore, such a serum still retains the major part of its agglutinating antibody. The purpose of this paper is to record the influence of ketene on the protective power of antipneumococcus serum.

Type I antipneumococcus horse serum, containing 200 units per cc (1642-1, Eli Lilly and Co.) was tested. To 10 cc of the serum to be ketenized, 0.6 g of NaHCO₃ was added to buffer the acetic acid which is formed during the process. A drop of caprylic alcohol was introduced to prevent foaming. Ketene gas was passed through the serum for 35 min at the rate of 100 bubbles per min (diam of inlet tube, 4 mm). At the end of the ketenizing process the pH of the serum was 7.8. Both the ketene treated and the original antisera were diluted with 0.85% physiological salt solution until 1 unit was contained in 0.5 cc. In this test a constant amount of serum and varying amounts of culture were used.

A New York State Laboratory strain, pneumococcus type I “N” (Neufeld) bacterial collection No. 1 was employed. The first blood-broth transfer of a heart-blood culture from a mouse dying within 48 hr after intraperitoneal inoculation of 0.00000001 cc of culture was used in the test. Organisms were cultured in double infusion blood-broth for 16 hr at 37°C. All dilutions were made in broth so that the desired amount of culture was contained in 1.0 cc.

On the assumption that each pneumococcus colony represents the growth from one organism, the number of pneumococci per cubic centimeter was determined by triplicate blood agar pour plates at the time of the test by the use of 1.0 cc each of 10^-7, 10^-8, and 10^-9 dilutions of the culture; the colonies were counted after 48 hr incubation.