Group A Hemolytic Streptococci. I. A Chemically Defined Medium for Growth from Small Inocula

Abstract

Defined media which allow heavy growth of group A streptococci were developed. They consisted of either 21 amino acids, glutamine, 6 vitamins, salts, purines, pyrimidines and glucose or 13 amino acids and 4 vitamins. Cysteine was important both as an essential amino acid and as a reducing agent. As an amino acid only a small amount (10 [mu]g/ml) was needed and this could be substituted by an equivalent amount of cystine. As a reducing agent it could be replaced by ascorbic acid and less effectively by thiomalic or thioglycollic acids. Concentration of cysteine was critical for initiation of growth from small inocula. With less than 5 x 106 /ml cells at least 350 [mu]g/ml cysteine HC1 were needed for obtaining visible growth. Pyridoxal was necessary in a medium of 13 amino acids and 3 vitamins (nicotinic acid, pantothenate, riboflavin) whereas in a complete medium (22 amino acids) no need for pyridoxal was found. Pyridoxal could be replaced by L- or DL-alanine.