Ganciclovir resistance and UL97 gene mutations in cytomegalovirus blood isolates from patients with AIDS treated with ganciclovir.

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Treatment of cytomegalovirus (CMV) diseases with protracted administration of ganciclovir can promote the development of resistant CMV that is associated with a poor response to therapy. It has been shown that the majority of ganciclovir-resistant CMV isolates carry mutations in the UL97 phosphotransferase gene. To evaluate the frequency of CMV resistance to ganciclovir in patients with AIDS treated with ganciclovir and to identify the UL97 gene mutations associated with ganciclovir resistance. Analysis of CMV blood isolates obtained over 1 year from patients treated with ganciclovir. CMV susceptibility to ganciclovir was determined by an immediate early antigen plaque reduction assay; UL97 gene mutations were identified by restriction enzyme digest analysis and sequencing. Twenty-nine patients were followed-up; 17 CMV blood isolates were obtained from 10 ganciclovir-experienced patients. Thirteen (76%) of these isolates, obtained from seven (24%) patients after a median treatment duration of 5.5 months, were resistant to ganciclovir. Five of the seven patients who had a ganciclovir-resistant CMV in blood showed retinitis progression. UL97 gene mutations were identified in nine CMV isolates at codons 460 (M --> V), 594 (A --> V and A --> T), and 595(L --> S). Three patients developed a ganciclovir-resistant virus after a ganciclovir treatment shorter than 60 days (28-58 days). In another patient, we observed that ganciclovir resistance persisted 4 months after discontinuation of ganciclovir therapy. Our results indicate that ganciclovir resistance due to UL97 gene mutations is common in subjects with AIDS-related CMV diseases treated with ganciclovir. Detection of these mutations represents a tool for the management of patients with ganciclovir therapy.