Source Department of Immunology, Microbiology and Parasitology, Medicine and Odontology Faculty, University of Basque Country (UPV/EHU), Sarriena Auzoa, 48940 Leioa-Bizkaia, Spain.

Background. Long-term lamivudine (LAM), adefovir (ADV) and entecavir (ETV) treatment induce the emergence of drug-resistant hepatitis B virus (HBV) in patients with chronic hepatitis B infection.

Aim. To evaluate the LAM, ADV and ETV resistance mutations detected in our patient group.
Materials and methods.Twenty patients who had received at least two years of treatment with nucleoside/tide analogues were enrolled in this study. Patients with detectable HBV DNA were analyzed in order to detect resistance mutations and in this group of patients treatment was change.

Results. Three patients developed LAM resistance mutations (2 presented rtM204I and one rtL180M+rtM204V/I) and one patient showed rtN236T ADV resistance mutation. During ADV and LAM treatment, one patient developed ADV plus LAM resistance mutations (rtI163V+rtL180M+rtA181V+rtN236T), in this case, HBV strains harbouring polymerase mutations did not develop LAM associated rtM204V/I primary mutation. In addition, ETV resistance mutations (rtL180M+rtT184A+rtS202G+rtM204V) were detected in one patient.

Conclusions. These findings suggest that monotherapy resulted in a limited virological response and combination strategies including potent antiviral agents should be recommended for patients with resistant mutations.