Comparative Observations on Bacteriolytic and Hemolytic Titers of Certain Sera

The Bordet Gengou reaction was designed to test the hypothesis of the identity of bacteriolytic and hemolytic complement, 1 although Bordet recognized later that the identity could not be regarded as absolute, since he was able to make specific anticomplements for the sera of various animals. 2 Muir and Browning 3 suggested that the bactericidal action of normal serum might be due to some moiety of complement which they termed “bacteriophilic”. Gordon and his coworkers 4 have been unable to obtain a serum which is devoid of hemolytic complement and yet possesses bactericidal action, though the reverse might be true of sera absorbed with bacteria, unless absorption were continued too long or the number of bacteria used were overwhelming.

A series of tests was made to determine which bacteria in the School collection could be depended upon to resist the bactericidal action of certain non-immune sera, and which bacteria were sensitive to it. The results with pooled human sera did not vary, but occasionally an organism was killed by some rabbit sera and not by others (e. g., B. enteritidis, B. typhosus Rawlins). Table I is a. resume of these tests.

The technique used was as follows: The bacterial suspensions, from 18-hour cultures on agar slants, were made in saline containing 0.1% gelatin. Very few bacteria survived incubation in saline, but the addition of this very small amount of gelatin removed the toxicity of the saline. The first dilution was made to correspond with Tube 1 of the McFarland nephelometer, the final dilution was one ten-thousandth of the first. The number of bacteria on control plates without serum was 1,000 to 2,000 per cc., 1 cc. being the amount of suspension used in the tests. The mixtures of bacteria and serum were incubated for 4 hours in a waterbath at 37.5°C, and the entire mixture was plated by pouring.