Studies on Variability of B. diphtheriae

Abstract

Typical cultures of virulent diphtheria bacilli grown in broth containing 10% specific antibacterial serum gave origin to distinct and rather stable variant types differing markedly from the parent strain in colony form, lacking in fermentative properties and in virulence and toxigenicity. Likewise, continued cultivation of typical cultures (at 37°C.) in broth containing 0.1% phenol, of 0.5% lithium chloride or 2.5% pancreatin as well as cultivation in K-medium (Kendall) diluted 1 :3 with physiologic salt solution and cultivation in plain broth at 45°C., gave rise to the development of similar variant types.In some instances transformation from the original characteristic colony type to the variant type occurred suddenly while in other instances certain variations or intermediate changes in colony form with loss of virulence were noted before the appearance of the extreme variant type. The intermediate types probably corresponded to those noted by other observers of bacterial dissociation in B. diphtheria...