Susceptibility of HSV strains from patients with genital herpes treated with various formulations of acyclovir

Virus isolates from 55 patients with recurrent or first-episode genital herpes, treated with various formulation of acyclovir, were tested for their susceptibility to the drug. In all but one of these patients pre-treatment isolates were available for comparison with later isolates. In none of patients, even those receiving long-term prophylaxis, was the susceptibility of the post-treatment isolates significantly reduced.