Antiviral resistance in cytomegalovirus: an emerging problem in organ transplant recipients

In the era of more aggressive immunosuppressive regimens and antiviral prophylaxis, ganciclovir-resistant cytomegalovirus (CMV) has been recognized as an important clinical problem in organ transplant recipients. Among the various solid-organ transplant (SOT) recipients, lung transplant recipients appear to be disproportionately affected. Ganciclovir-resistant CMV appears to be a relatively late posttransplant complication and is seen predominantly among CMV-seronegative recipients of organs from seropositive donors, particularly in the setting of potent immunosuppression and prolonged exposure to ganciclovir (especially oral ganciclovir). Limitations in current diagnostic methods mandate a high clinical index of suspicion. In high-risk patients in whom ganciclovir resistance is clinically suspected, while awaiting laboratory confirmation of resistance, empiric addition of intravenous foscarnet, often combined with reduction in immunosuppression and CMV hyperimmune globulin, are commonly used. Better diagnostic tools and newer, less toxic, antiviral agents with different mechanisms of action are urgently needed to decrease the morbidity associated with this complication in organ transplant recipients.