Nosocomial spread of hepatitis B virus in two hemodialysis units, investigated by restriction fragment length polymorphism analysis

A method for genotyping hepatitis B virus (HBV) strains, based on restricti on fragment length polymorphism (RFLP) analysis of four different amplified fragments of the HBV genome, was used to investigate nosocomial infections that occurred in two Brazilian hemodialysis centers. Viral isolates from h epatitis B surface antigen (HBsAg)-positive serum samples from 27 hemodialy sis patients and 39 HBV-positive unrelated control patients were grouped ac cording to their RFLP patterns. Strains isolated from the control patients were divided into nine RFLP patterns: A1, A2, A3 (genotype A), D1, D2, D3, D4 (genotype D), F1, and F2 (genotype F). In hemodialysis unit A. (Rio de J aneiro), 14 HBV isolates were grouped into five different RFLP patterns: Al , A2, A3, D3, and D4. Pattern A2, present at a relatively low prevalence (1 8%) in the control group, was observed in the majority (53%) of the hemodia lysis patients. Notably, all five patients who seroconverted to HBsAg posit ivity in 1995 carried the strain A2. In hemodialysis unit B (state of Sao P aulo), where an outbreak of HBV infection occurred in 1996-1997, RFLP analy sis showed that all 13 patients who seroconverted were infected with HBV is olates of genotype D. Coinfection with strain A1 was detected in seven of t hem. The results demonstrate the value of RFLP analysis in establishing com mon sources of infection in hemodialysis centers.