Table 1.

Sensitivity of laboratory HCMV strains and patient isolates to ganciclovir and cidofovir as indicated by HCMV LA expression in human foreskin fibroblasts infected at MOI 0.02 120 h post infection. Concentrations that reduce LA expression by 50% (IC₅₀) are provided.

		IC50 (µM)	IC50 (µM)
Virus Strain/Isolate	Resistance Mutations	Ganciclovir	Cidofovir
Hi91	n/a	0.71 ± 0.57	0.31 ± 0.14
Davis	n/a	0.72 ± 0.31	0.17 ± 0.02
Towne	n/a	0.61 ± 0.12	0.14 ± 0.01
U1	A987G *, C607Y **	24 ± 10	5.2 ± 1.9
U59	A987G	23 ± 14	1.6 ± 0.5

* mutation in the HCMV DNA polymerase UL54, which confers resistance to ganciclovir and cidofovir [42,43]. ** mutation in the HCMV kinase UL97, which is associated with ganciclovir resistance [44,45].