Injury of myelin sheaths in isolated rabbit vagus nerves by alpha-toxin of Staphylococcus aureus.

S. Szmigielski, M. Blankenship, J. P. Robinson and S. Harshman. Injury of myelin sheaths in isolated rabbit vagus nerves by α-toxin of Staphylococcus aureus. Toxicon17, 363–371, 1979.—Dissected rabbit vagus nerves were incubated in vitro with 0·24-4 μg of purified staphylococcal α-toxin (17,000 H.U./mg protein) per ml. The release of ⁸⁶Rb from prelabeled nerves and the electrical activity of nerves (action potential) were measured and correlated with morphological changes observed by electron microscopy. At a concentration of α-toxin of 2 μg/ml, 30% of incorporated ⁸⁶Rb was released from the nerves after 30 min of incubation. The electrical activity was maintained over this time period and required an additional 30 min before failing completely. Concentrations of α-toxin below 2 μg/ml had no effect on either the release of ⁸⁶Rb or the electrical activity even after 60 min of incubation of the nerves. In contrast, dramatic changes in the morphology of the myelin sheaths are readily demonstrated after 30 min of incubation and can easily be observed at 0·2 μg/ml, a level of α-toxin which has no effect on ⁸⁶Rb release or electrical activity. Both non-myelinated nerve fibers and Schwann cell membranes appear to be more resistant to the action of α-toxin. We conclude that, of the parameters measured, disorganization of myelin sheaths is the first recognizable symptom of injury to peripheral nerves by staphylococcal α-toxin.