Sensitivity monitoring of herpes simplex virus isolates from patients receiving acyclovir.

A simple plaque-reduction assay was used to determine the acyclovir sensitivity of herpes simplex virus isolates taken from patients enrolled int he acyclovir clinical trial programme. The resultant data revealed no reduction in acyclovir sensitivity in virus from those patients, with a normal immune status, receiving topical, oral or intravenous acyclovir for the treatment of acute disease episodes. In the treatment or prophylaxis of chronic herpes infections in immunocompromised patients reductions in sensitivity were observed but these were infrequent. Sensitive virus was later recovered from a small number of patients who had yielded resistant virus when they were followed through to the next recurrence.