Staphylococcal carriage and infection in myasthenia gravis patients receiving therapeutic apheresis.

Populations exposed to repetitive needle puncture (such as hemodialysis patients, insulin-dependent diabetics, and parenteral drug abusers) are at increased risk for nasal carriage of Staphylococcus aureus. These groups appear to have increased susceptibility to serious staphylococcal infection as well. We performed a microbiologic survey on a group of patients receiving regular, long-term therapeutic apheresis for myasthenia gravis (MG), and compared the rate of nasal staphylococcal carriage with that found in control groups of MG patients not receiving apheresis and ambulatory general medical patients without known risk factors for staphylococcal carriage. Medical records were reviewed for episodes of significant staphylococcal infection occurring since commencement of apheresis. Nasal S. aureus carriage was found in 9/29 (31%) apheresis patients, 8/30 (27%) MG controls, and 8/30 (27%) general medical controls. No significant difference in frequency of apheresis was noted between carriers and noncarriers. A single episode of S. aureus bacteremia occurred in 95 patient-years of apheresis therapy. We conclude that therapeutic apheresis for MG does not increase the risk of staphylococcal carriage, and that serious infection is infrequent.