摘要AIM: To investigate the epidemiology of hepatitis B virus (HBV) strains with a mutation at nt551 in surface gene among hepatitis B patients in Nanjing and its neighbourhood.METHODS: By using mutation-specific polymerase chain reaction (msPCR) established by our laboratory for amplifying HBV DNAs with a mutation at nt551, 117 serum samples taken from hepatitis B patients were detected.RESULTS: The results showed that 112 samples were positive for nt551A, 4 samples were positive for nt551G.One sample was positive for nt551T. No nt551C of HBV DNA was found. The incidence of HBsAg mutants with G,C, T, A at nt551 among 117 samples was 3.42%, 0%, 0.85%,95.73%, respectively.CONCLUSION: In Nanjing and its neighbourhood, hepatitis B patients are mainly infected with wild genotype HBV.The incidence of mutants with a mutation at nt551 in HBV genome is significantly lower than that in wild genotype HBV DNA (P＜0.01). The necessity of adding components of HBsAg mutants to HBV vaccine needs further investigation.