Investigation of aciclovir-resistant herpes simplex virus I infection in a bone marrow transplantation unit: genotyping shows that different strains are involved.

Over an eight-month period from October 1997 to May 1998, four patients who had received a bone marrow transplant (BMT) from an unrelated donor presented with severe mucosal cutaneous infections involving aciclovir resistant herpes simplex virus 1 (HSV-1). The emergence within a short period of resistant HSV-1 strains in the bone marrow transplantation unit raised fears of hospital-acquired infections. The hypothesis was investigated by restriction fragment length polymorphism (RFLP), sequencing of the thymidine kinase (TK) gene and genotyping of hypervariable regions of these four strains. Restriction fragment length polymorphism proved to be poorly discriminant and the TK sequence did not rule out transmission between these patients. Amplification of reiterating hypervariable genomic HSV-1 regions designated Re IV and Re VII clearly differentiated patients' strains. Thus, in this study, there was no evidence of nosocomial transmission of HSV-1 strains between the four patients.