Effect of moist heat sterilisation on the pyrogenicity of cell wall components from Staphylococcus aureus

As opposed to endotoxins very little is known about the heat resistance of Gram positive pyrogens. The aim of this study is to examine the pyrogenic activity of the cell wall components lipoteichoic acid and peptidoglycan from Staphylococcus aureus after moist heat sterilisation. The pyrogenic activity is determined as the ability of the substances to induce interleukin-6 secretion in Mono Mac 6 cells.The standard terminal moist heat sterilisation procedures (121 °C for 15 min and 134 °C for 3 min) are not able to inactivate the pyrogenic activity of S. aureus lipoteichoic acid and peptidoglycan. However after longer treatment times the pyrogenic activity of lipoteichoic acid is removed at both 121 °C and 134 °C. In contrast the activity of peptidoglycan is not removed after 160 min at neither 121 °C nor 134 °C where only a 2-log reduction is obtained. In conclusion the terminal moist heat sterilisation procedures described by the European Pharmacopoeia are not able to inactivate the interleukin-6 inducing activity of S. aureus lipoteichoic acid and peptidoglycan.