Activity requirements of epidermolytic toxin from Staphylococcus aureus studied by an in vitro assay

The activity of epidermolytic toxin from Staphylococcus aureus was studied in vitro using discs of neonatal mouse skin. By assessing the loss of skin integrity as a function of toxin dose and time, it was possible to put the assay on a semi-quantitative basis. Epidermolysis occurred without any change in rate from pH 3.8 to 8.7, and at an increasing rate in the temperature range of 0-37 degrees C. Activity was observed even at the lowest temperature. More than 30 inhibitors of energy metabolism, central metabolic pathways, receptor binding or proteolysis, individually failed to prevent epidermolysis and it is suggested that intoxication cannot be dependent on receptor-mediated endocytosis. Five metal-ion chelators inhibited epidermolysis, due to an effect on the tissue rather than on the toxin. Using X-ray fluorescence and atomic absorption spectroscopy, it was shown that epidermolytic toxins do not contain any essential metal ions. Some transition metals, but not Ca2+ or Mg2+, prevented the chelator-dependent inhibition of epidermolysis.