Retinitis and Viral Resistance Study Group Departments of 1Ophthalmology and 2Medicine, Johns Hopkins

Cytomegalovirus (CMV) retinitis is among the most common opportunistic infections in patients with acquired immunode®ciency syndrome. In a prospective study of 210 patients with CMV retinitis, 26 were identi®ed as having either a phenotypic or a genotypic ganciclovir-resistant isolate from either blood or urine cultures. For blood culture isolates with an IC50 16.0 mm for ganciclovir, the sensitivity and speci®city for detecting a UL97 mutation were 95 % and 98%, respectively, whereas for an IC50 18.0 mM they were 79 % and 99%, respectively. Although there were trade-offs between the 2 thresholds for blood culture isolates, for urine culture isolates an IC50 18.0 mM appeared to be better at identifying genotypic resistance. UL97 mutations identi®ed in both the blood and urine cultures of individual patients were identical in 87.5 % of cases. High-level ganciclovir resistance (IC50, 130 mM) typically, but not invariably, was associated with a mutation in both the UL97 and UL54 genes. Cytomegalovirus (CMV) retinitis is the most common intra-ocular infection in patients with AIDS [1]. Untreated, CMV retinitis is a progressive disease, which results in total retinal destruction and blindness [1]. As of September 2000, 4 drug