Iron and glucose affecting growth and haemolysin production in human strains of group B streptococci

Seven strains of group B streptococci aetiologically related to humans were investigated in order to observe the role of glucose and medium iron on their growth and haemolysin production, and the necessity of a 'carrier' molecule to ensure the stability of the haemolysin. Both growth and haemolysin production were significantly influenced by glucose and medium iron concentrations. Iron concentrations between 5 and 7 micrograms/ml and 0.5% to 1% glucose were critical. Maximum haemolysin production (detected by lysis of sheep erythrocytes) was obtained during the late exponential phase of the growth cycle, but declined, producing sigmoidal-like curves as the organism entered the stationary phase. RNA-core, serum and bovine serum albumin, stabilizers of streptolysin S had no stabilizing effect for the haemolysin of group B streptococci. However, bovine serum albumin-starch mixture (0.5% bovine serum albumin and 0.5% starch in phosphate buffered saline or brain-heart infusion) was an effective stabilizer.