Survival of Ehrlichia chaffeensis in refrigerated, ADSOL-treated RBCs

BACKGROUND: The purpose of this study was to investigate the persistence of viable Ehrlichia chaffeensis in ADSOL-treated RBCs stored at 4 to 6 degree s C. STUDY DESIGN AND METHODS: The continuous monocytic cell lines THP-1 and DH8 2 were infected with E.chaffeensis (St. Vincent isolate). Packed RBC units were inoculated in separate experiments with E. chaffeensis-infected cells as final concentrations of 8.02 x 10(4) (DH82) and 1.43 x 10(4) (THP-1) inf ected cells per mi. Aliquots were stored at 4 to 6 degrees C for 1 to 42 da ys. At selected intervals, nucleated cells from the RBC aliquots were obtai ned by using a ficoll-isopaque separation procedure. Uninfected DH82 cell c ultures were inoculated with the harvested nucleated cells or supernatant. The cell cultures were evaluated for infection by weekly examination of Wri ght's (Diff-Quik) stained cytocentrifuged slides. PCR amplification was als o used to test the harvested nucleated cells or supernatant for the presenc e of E.chaffeensis DNA. RESULTS: In both types of infected cell lines, E. chaffeensis was reisolate d in DH82 cells for as long as 11 days from the cellular fraction and for u p to 5 days from the supernatant fraction. PCR results were positive throug hout the 42-day testing period. CONCLUSION: Cell-associated E.chaffeensis remains viable in ADSOL-treated R BCs stored at 4 to 6 degrees C for at least 11 days. These data suggest tha t transfusion-acquired infection is possible. Successful reisolation was ac hieved from the supernatant fraction, which suggests that RBC products trea ted with a WBC-reduction procedure may still present a risk for transfusion transmission. No correlation between PCR positivity and viability of bacte ria was noted.