Phenotypic Evaluation of Previously Uncharacterized Cytomegalovirus DNA Polymerase Sequence Variants Detected in a Valganciclovir Treatment Trial

Background. In a large randomized trial comparing oral valganciclovir and intravenous ganciclovir for treatment of cytomegalovirus disease in solid organ transplantation, confirmed genotypic drug resistance was uncommon (20 sequence variants, including the nonviable mutations and several resistance mutations. Conclusions. Newly phenotyped UL54 sequence variants did not significantly change the reported incidence of drug resistance in the clinical trial. Unrecognized sequence variants in diagnostic genotyping reports should be confirmed by additional testing in order to improve clinical decision making.