Prevalence of antiviral drug resistance in untreated patients with cytomegalovirus retinitis

The purpose of this study was to determine the prevalence of UL97 resistance mutations in cytomegalovirus (CMV) DNA amplified from the eyes of patients with AIDS and newly diagnosed CMV retinitis. Relevant segments of the CMV UL97 gene were amplified from vitreous humor, after which restriction digest screening was performed for resistance mutations at codons 460, 520, 591, 592, 594, 595, and 603. Mutations were confirmed by DNA sequencing. Vitreous from 21 eyes with AIDS-related non-CMV viral retinitis served as negative controls. CMV DNA was successfully amplified from 195 of 204 eyes. A resistance mutation was found in only a single eye, a T-->G mutation at base 1774, predicting a cysteine to glycine mutation at codon 592. The prevalence of UL97 resistance mutations in the eyes of patients with newly diagnosed CMV retinitis is very low.