Variations in the streptolysin curve in serum media

Abstract

In the growth of hemolytic streptococci in serum media, the hemolysin, titrated from hour to hour, shows a gradual ascending curve of concentration which reaches a maximum at about the sixth to the twelfth hour of growth, and then falls rapidly. This curve may be modified by the character of the culture used to seed the media, by the quantity of serum present, the source of the sera, and the amount of peptone in the broth. There are two variations which occur; variations in concentration of hemolysin, and in the time that hemolysin first appears in the culture and later the time at which the maximum amount can be demonstrated. With similar seeding, and only one variant introduced in experiments, these variations are brought out very sharply. Cultures in 20 per cent. rabbit serum and horse serum in broth without peptone show that rabbit serum media allows the production of the lysin sooner and does not give as great concentrations as horse serum. The lower percentages of these sera, when seeded with different plain broth cultures give greater variations in the maximum titre, but these variations are largely obviated in 20 per cent. media. Twenty per cent. horse serum gives practically constant titres at some time during the growth. The time relationships hold in all concentrations. Peptone (2 per cent.) slightly increases the titre and gives identical titres in 20 per cent. horse serum, and brings the variations within closer limits in rabbit serum media. The time relationships are directly dependent on the growth of the streptococci, so that the delay in lysin production in horse serum indicates a lag in the rate of multiplication during the early hours after seeding.