Contribution to study of diphtheria toxin

Abstract

The results reported are those of experiments planned to throw further light on the mechanism of toxin production by B. diphtheria.

An extended series of test-tube experiments was carried out in which the Park 8 strain of the diphtheria bacillus was grown in broth and daily counts made of the number of viable organisms (as estimated by the poured plate method), and at the same time the toxicity of the broth, free from organisms, was estimated.

The growth curve had the characteristics of those reported at various times in the literature for other organisms; i.e., a period of logarithmic growth, and then a continued rise which in general reached a maximum in 48 hours, a sudden falling off of the number of viable organisms and then a more gradual decrease, with some-times small increases in the number of viable organisms during the period of decrease similar to the observations of Graham-Smith 1 for staphylococcus. It is suspected that these small secondary increases may only be apparent, and are due to the method of counting. The toxicity of the broth was very low at the end of 24 hours (approx. 1 M.L.D. per 0.5 c.c.), with a small increase at the end of 48 hours and then a rapid increase (if the increase and decrease of the cells was characteristic), and after a maximum was reached a falling off in toxicity which was sometimes very sudden. This sudden falling off in toxicity has also been reported by Bunker. 2

The hydrogenion concentration of the broth during growth showed an initial increase and then a gradual falling off; this agrees with the findings of Bunker 2 and Davis. 3 Bunker in his paper gives the limits of maximum toxicity at P_H 7.8 − 8.25; contrary to this, good toxin has continued to be formed at P_H 8.7