Detection of Staphylococcus aureus in peripheral blood stem cell cultures after sterilization of standard blood cultures.

We report central venous catheter (CVC)-associated Staphylococcus aureus bacteremia detected by apheresis product culture after sterilization of standard blood cultures. A 64-year-old man with non-Hodgkin's lymphoma underwent peripheral blood stem cell (PBSC) collection. Five days after placement of a CVC, inflammation was evident at the insertion site. The CVC was removed and cephalexin was begun. Discharge at the site contained neutrophils and gram-positive cocci in pairs and clusters. Cultures of the discharge, of blood drawn via the CVC, of the CVC tip and of the apheresis product collected that day grew methicillin-susceptible S. aureus (MSSA). Cephalexin was discontinued in favor of oxacillin. Three days after removal of the CVC, PBSC collections were resumed via a contralateral CVC. Three sets of standard blood cultures drawn the day the new CVC was placed and the following day were negative, yet apheresis product cultures from each of these days grew MSSA. PBSC collections were halted, the CVC was removed, and oxacillin was continued via a peripherally inserted central catheter. Transesophageal echocardiography after two weeks of therapy revealed thickened mitral leaflets and damage to the posterior leaflet. Transthoracic echocardiography 11 weeks preceding this study had demonstrated normal mitral valve anatomy and function. Oxacillin was continued for six weeks, after which PBSC collections were resumed. Pulsed-field gel electrophoresis of the MSSA isolates revealed a clonal pattern. Cultures of apheresis product may be more sensitive to the presence of bacteremia than standard blood cultures, and they should guide clinical decisions when the bacteria isolated are potential pathogens or suggest clinical infection.