OBJECTIVESTo analyze HBV drug-resistant mutations against nucleos(t)ide analogues at 12 reported sites in 340 patients with chronic hepatitis B.

METHODSSerum HBV DNA was extracted and a nested PCR assay was employed for the reverse transcriptase (RT) gene amplification. Direct sequencing of PCR product was performed. The significance of detected mutations was analyzed in view of clinical data of the patients.

RESULTSDrug-resistant mutations were detected in 68 patients taking lamivudine (LAM), 10 taking adefovir (ADV), 8 taking entecavir, and 1 taking telbivudine (LdT). M204V and M204I were the most common LAM-resistant mutations. The former usually emerged with L180M while the latter often emerged alone. N236T +/- A181 substitution was the most frequently seen ADV-resistant mutation. ETV-resistant mutations occurred on the basis of LAM-resistant mutations and T184 change was the most common form. LdT-resistance was observed as M204I. Interestingly, these drug-resistant mutations were detected in a few patients who had not been treated with nucleos(t)ide analogues.

CONCLUSIONDetection of HBV drug-resistant mutations at multiple sites of the viral RT gene is valuable for discovering and verifying drug resistance and thus is very helpful in planning anti-HBV therapy.