The effect of glycerol monolaurate on growth of, and production of toxic shock syndrome toxin-1 and lipase by, Staphylococcus aureus.

The effects of glycerol monolaurate on the growth of, and production of Toxic Shock Syndrome Toxin-1 (TSST-1) and lipase by, Staphylococcus aureus FRI 1187 were investigated in batch and continuous culture models using a defined synthetic medium. The growth and yield of S. aureus depended on glycerol monolaurate concentration, pH of the environment and the inoculum size. The MICs for glycerol monolaurate of 29 S. aureus isolates, determined in a complex medium, were between 10 and 20 mg/L with a 10(3) to 10(4) cfu inoculum; a 1000-fold increase in inoculum size increased the MIC five-fold. In continuous culture, glycerol monolaurate increased the cell yield of S. aureus. In batch cultures with 17 mg/L glycerol monolaurate, TSST-1 and lipase production by S. aureus was delayed and their specific production was not decreased compared with cultures without glycerol monolaurate. At 150 mg/L glycerol monolaurate, growth and toxin production were decreased. The lipase of S. aureus hydrolyzed glycerol monolaurate. The reduction of toxin production was associated with effects on S. aureus growth, and these effects might have been relieved after lipase had been produced.