Pathogenicity of Different Types of C. diphtheria for Chinese Hamsters

Abstract

Since Anderson, et al., 1 described 3 types of C. diphtheria, the relative virulence of these organisms for common laboratory animals has been the subject of much study. Povitsky, Eisner, and Jackson 2 observed that it took 4 times smaller dose of grams than mitis types to kill guinea pigs. Murray 3 showed that in virulence for rabbits, the order was gravis, intermediate, mitis. Gundel and Ezrin 4 found that the organisms of the gravis type were not only more virulent than those of intermediate and mitis types, but definitely more invasive in guinea pigs. However, Parish and his coworkers 5 could demonstrate no such high virulence of the gravis type either in rabbits or in guinea pigs. In view of such conflicting reports, a further study of this problem in another species of laboratory animal seems to be desirable. As the Chinese hamsters have been found to be highly susceptible to C. diphtheria infection, and since they can be easily procured in large numbers and at low cost, 6 these animals have been chosen for the present study.

Eight strains of gravis, 5 of intermediate, and 8 of mitis types were employed. Two of each type were kindly supplied by Professor McLeod of the University of Leeds and the rest were isolated locally from cases of diphtheria. Eighteen-hour Loeffler's slant-cultures were emulsified in 2 cc. normal saline and shaken vigorously in order to produce an even suspension. An approximately equal concentration of organisms was obtained by diluting the different cultures to an equal opacity. These suspensions were then diluted 10, 100, and 1000 times with normal saline. Two-tenths cc. of the original suspension and of each dilution were inoculated intramuscularly into 5 hamsters each weighing from 25 to 30 gm.