RESISTANCE OF BACTERIA 207 



Experimenting with B. dysenteriae, I was the first to show^'^ that all 

 of the colonies which appeared on agar were ultrapure, that is to say, 

 contained only bacteria with a complete absence of bacteriophage 

 corpuscles. Bordet and Ciuca^' working with B. coli were, on the other 

 hand, the first to find that all of the colonies obtained after seeding 

 a secondary culture were contaminated with the bacteriophage. 

 Kuttner^^* working with B. typhosus has shown that in reality one may 

 find two types of colonies, ultrapure colonies and contaminated colonies. 

 And shortly after this, Bordet and Ciuca^^ reported that there are three 

 types of colonies: (a) ultrapure colonies formed of resistant bacteria; 

 (6) contaminated colonies containing resisting bacteria and the bacterio- 

 phage, and (c) ultrapure colonies which contain only susceptible bacteria. 



It is probable that these last are in reality colonies formed by bacteria 

 with a very low resistance but it is doubtful if they are entirely devoid of 

 resistance. Bruynoghe,"^ has, as a matter of fact, shown that one may 

 find a whole scale of resistance, from colonies composed of refractory 

 bacteria up to those in which the resistance is so weak that it is only 

 manifest by a very insignificant retardation in bacteriophagy. The 

 proportion of contaminated colonies in relation to the number of ultra- 

 pure colonies is extremely variable. It varies on the one hand with the 

 degree of resistance of the bacterium and on the other with the duration 

 of the symbiosis. Bruynoghe and Maisin^^^ report that with a secondary 

 culture of B. coli seeded upon agar they did not find a single contam- 

 inated colony among the 30 which they examined. In another experi- 

 ment performed with Shiga bacilli 9 of 10 colonies were ultrapure, one 

 only was contaminated. We will see on the other hand that when the 

 symbiotic association has continued for a long time it may be very 

 difficult to obtain ultrapure colonies. In this last case it is necessary to 

 adopt special methods of isolation. 



If we make a preparation for procuring isolated colonies from a colony 

 of low resistance we will find that all of the colonies which are derived 

 from it are likewise either lacking in resistance or present a very low 

 resistance, usually somewhat below that of the bacteria of the original 

 colony. On the contrary, if we secure, also by the method of colonies, 

 ultrapure colonies possessing a high resistance the result is exactly the 

 same as though we had made the planting directly from the secondary 

 culture, that is, the majority of the colonies are formed of bacteria 

 having little or no resistance while some few are made up of bacteria of 

 high resistance. This shows us that in a colony, which tested as a whole 

 appears to be resistant, the resistance actually belongs to some few of the 



