Dissociation of Diplococcus from Measles

Abstract

Stimulated by Hadley's 1 article on microbic dissociation, 12 tried by environmental conditions to incite a dissociation of measles cocci. No change in morphology or type of colony was demonstrated, but under the influence of normal and immune horse serum, and high temperature 40-41 C. for 24 hours, these cocci completely lost their specificity as determined by the opsonic method. Their specificity was quickly restored by transplanting them again onto blood agar and growing 'at 36 C. Recently a measles diplococcus was grown for 4 days instead of 1 day at 40 C. and although it was transferred for 22 generations on blood agar at 36 C, its specificity was not restored. Again no change in morphology or type of colony was observed. After some strains of measles diplococci have been isolated several years the growth on blood agar is seen to be less green, moister and more abundant, with a partial zone of hemolysis around the colonies, while the cocci grow in clumps and pairs and now show no chain formation. The cocci are more phagocytable, so that it is necessary to use very thin suspensions in order to demonstrate differences between the opsonic specimens containing normal and immune serum. One strain which for years grew in this way, when cultured for 24 hours in oxalated sheep blood and dextrose broth equal parts, repeatedly developed long chains and capsules. In this medium many of the cocci were seen inside leukocytes. When plated on sheep blood agar, two types of colonies were seen, a fairly large smooth, green colony with a narrow zone of partial hemolysis and a large, smooth, moist, less green colony without the zone of hemolysis. The cocci from the large hemolytic colony were more in clumps, those in the large nonhemolytic colony were more in pairs; the cocci from the former colony were much more phagocytable than those from the non-hemolytic colony, in the presence of both normal and immune serum. This change or dissociation appeared to be due to the presence of fibrin with leukocytes in