Effect of water activity on enterotoxin B production and growth of Staphylococcus aureus

Abstract

Staphylococcus aureus C-243, an enterotoxin B-producing strain, was cultured on media adjusted to various water activity (a(w)) levels by means of two different solute systems. Total numbers and rate of growth were diminished at low a(w) levels, and enterotoxin synthesis was extremely sensitive to reduction in a(w). A reduction of a(w) from 0.99 to 0.98 in one medium and from 0.99 to 0.97 in the other medium resulted in extremely low levels of enterotoxin in spent culture media despite the attainment of high numbers of staphylococci.