Multiple ganciclovir-resistant strains in a newborn with symptomatic congenital human cytomegalovirus infection

A case of human cytomegalovirus (HCMV) drug-resistance in a congenitally infected newborn is described. Unusual aspects of this case include: (i) the detection of an extremely complex virus population, composed of a mixture of wild-type (wt) and multiple mutant ganciclovir (GCV) and valganciclovir (val-GCV) resistant strains carrying a variety of known mutations in UL97; (ii) the identification of novel UL97 mutations and (iii) the first time detection of combined UL97 drug resistance mutations in the same viral strain. In detail, four known UL97 single-nucleotide mutations (A594T/V, M460V/I, C592G), a new amino-acid substitution (C607S), and a new deletion (597-600) in one of the three UL97 hot spots for GCV/val-GCV resistance (codons 460, 520 and 590-607) were detected. In addition, the combination of M460V + A594V and M460V + C592G was observed for the first time. The emergence of HCMV drug-resistance in symptomatic congenital infections chronically treated with GCV or val-GCV should be taken into account. The immaturity of the neonatal immune system may contribute to selection of complex virus populations in these patients. (C) 2012 Elsevier B. V. All rights reserved.