Nutritional Requirements of Enterotoxigenic Strains of Staphylococcus Aureus

摘要

In developing a synthetic medium for Staphylococcus aureus S-6, the following criteria were chosen: growth for 24 hr at 37 C with continuous shaking, minimum acceptable yield of 200 Klett Units. Growth was defined on the basis of these stringent, arbitrary criteria; positive growth was reported only if they were met. The defined medium developed was composed of inorganic salts, 11 amino acids (glycine, valine, leucine, threonine, phenylalanine, tyrosine, cysteine, methionine, proline, arginine, and histidine), and 3 vitamins, thiamine, nicotinic acid, and biotin. Biotin was a growth factor requirement in S-6 when glutamic acid but not glucose was used as a carbon source. The quantity of enterotoxin B was ca 7 times less in the defined than in complex medium, even though growth yields were similar. Any modification of the initial pH of the medium resulted in some loss of enterotoxin production, regardless of whether it was initially altered without further change, buffered with phosphate at constant level, or adjusted throughout the growth cycle by addition of acid or base. Both growth yield and toxigenesis were diminished at the two extremes of temperature, 15 and 43 C, tested; it is of practical importance that enterotoxin can be produced at these temperatures. Varying concentrations of CO2 in pure O2 were not beneficial for toxigenesis. With increased sparging of air or pure O2 into growing cultures, growth but not toxigenesis was stimulated; however, at high sparge rates, both were drastically reduced. An optimum air or O2 sparge-rate exists for growth or toxigenesis. (Author)