EXPERIMENT STATION BULLETINS. 633 



THE COMPARATIVE PATHOGEKICITY OF SEVERAL STRAINS 

 OF BACTERIUM ABORTUS (BANG) 



Technical Bulletin No. 55 



BY I. FOREST HUDDLESON 



Since the isolation and description of Bad. abortus by Bang in 1898, a large 

 number of strains have been isolated by various workers in this country and 

 in Europe. No data, however, have appeared which pertain to a study of 

 the pathogenic relationship and an attempt at grouping of the various strains 

 isolated. A study of this nature, if conducted upon suitable animals, should 

 reveal differences in the various strains of Bad. abortus as regards the pro- 

 duction of characteristic lesions or the symptom of abortion (premature 

 expulsion of the fetus). The above pathogenic properties of Bad. abortus 

 need no discussion as detailed descriptions and discussions of both have pre- 

 viously appeared in publications. 



It is a well known fact that individual members of a species of a micro- 

 organism may be so related that it is impossible to differentiate or group 

 them as to their pathogenic properties by studying their morphological, 

 cultural and biochemical characteristics. Such a differentiation of individual 

 strains may be made possible if their pathogenic properties are studied in 

 vivo. In other words, pathogenic and non-pathogenic, and intermediate 

 strains may be distinguished. Further, a loss of virulence as a result of long 

 cultivation upon an artificial medium may be discovered by studying the 

 pathogenic properties of each individual strain. 



The importance of a knowledge of the pathogenic properties of strains of 

 Bad. abortus becomes obvious when one desires to produce, experimentally, 

 abortion in pregnant animals, or to determine the efficacy of various pro- 

 phylactic and therapeutic measures in controlling the disease. 



A preliminary experiment was begun in the fall of 1916 to determine if 

 there was a difference in several strains of Bad. abortus as regards their 

 ability to produce lesions in the organs of guinea pigs following inoculation. 

 Several of the cultures used were isolated from material received at this 

 laboratory, and several were received from other laboratories. The experi- 

 ment was not completed at this time for various reasons, but the data col- 

 lected indicated that there was sufficient difference to warrant further study. 

 In January, 1920, the problem was again taken up for further study with 

 the same strains and additional strains. 



METHOD OF STUDY 



The guinea pig was used for these studies as its high degree of susceptibility 

 toward Bad. abortus as regards characteristic tissue changes had been demon- 

 strated in previous experiments. In order to produce these changes it is 

 necessary that the inoculum consist of the optimum number of living or- 

 ganisms. The dosage should not be too large. The writer has confirmed 



