Ganciclovir Susceptibilities of Cytomegalovirus (CMV) Isolates from Solid Organ Transplant Recipients with CMV Viremia after Antiviral Prophylaxis

Ganciclovir susceptibility studies were done on the last cytomegalovirus (CMV) isolate available from 42 solid organ transplant recipients with CMV viremia who were enrolled in a prospective CMV prophylactic trial. Viruses were categorized as follows: 13 isolates (group 1) from patients who received ganciclovir prophylaxis; 9 isolates (group 2) from patients who received acyclovir prophylaxis; 8 isolates (group 3) from patients who received acyclovir prophylaxis and ganciclovir treatment; and 12 isolates (group 4) from patients who received prophylaxis and treatment with ganciclovir. All CMV isolates were sensitive to ganciclovir (mean 50% inhibitory concentration [IC₅₀] = 1.7 µM; range, 0.2-5.3 µM). Mean IC₅₀ values (in µM) were 1.7 for group 1 isolates, 1.2 for group 2 isolates, 2.2 for group 3 isolates, and 1.7 for group 4 isolates (P>.05). Thus, acyclovir or ganciclovir prophylaxis in solid organ transplant patients did not select ganciclovir- resistant isolates of CMV.