Improvement of refractory acyclovir-resistant herpes simplex virus type 1 infection by continuous acyclovir administration.

Resistant herpes simplex virus type 1 (HSV-1) infection is sometimes fatal for immunocompromised patients. Here, we report 10-year-old girl receiving hematopoietic stem cell transplantation developed refractory HSV-1 infection, which was persisted to intermittent acyclovir (ACV) or foscarnet (FOS) administrations but was improved by continuous ACV administration. The isolates from the lesion were identified with low susceptibilities to ACV and FOS by plaque reduction assay due to DNA pol gene mutation. Continuous ACV administration overcomes the efficacy of intermittent administration and could be the best option to treat severe HSV-1 infectious patients.