Purpose: To report a case of acyclovir-resistant herpes simplex virus (HSV) keratitis after long-term, inconsistent use of topical acyclovir and fluorometholone.
Methods: A 70-year-old man with dendritic keratitis caused by an acyclovir-resistant HSV strain was examined. The 50% inhibitory concentration of different antiviral agents against the isolated virus and the DNA sequence of viral thymidine kinase were determined.
Results: The 50% inhibitory concentration of acyclovir and trifluorothymidine for the isolated HSV strain was 13.75 and 0.28 μg/mL, respectively, indicating that the virus was resistant to acyclovir. DNA sequencing of the viral thymidine kinase revealed that this virus had a frameshift mutant with a G insertion in the 7Gs homopolymer. Topical trifluorothymidine was effective, and the epithelial lesion was completely resolved within 2 weeks.
Conclusion: A typical form of dendritic keratitis was caused by an acyclovir-resistant HSV with frameshift mutation in a 7Gs homopolymer region.