Investigation of Borrelia burgdorferi genotypes in Australia obtained from erythema migrans tissue

摘要

Background: Lyme disease (LD) is an emerging infectious disease in Australia. There has been controversy regarding endemic lyme disease in the country for over 20 years. Borrelia burgdorferi sensu stricto (Bbss) and sensu lato (Bbsl) are closely related spirochetal species that are the causative agents of LD in humans. Clinical transmission of this tick-borne disease is marked by a characteristic rash known as erythema migrans (EM). This study employed molecular techniques to demonstrate the spirochetal agent of Lyme disease isolated from EM biopsies of patients in Australia and then investigate their genetic diversity.Methods: Four patients who presented to the author's practice over a one-year period from mid 2010 to mid 2011 returned positive results on central tissue biopsy of EM lesions using polymerase chain reaction (PCR) analysis. The findings were confirmed by DNA sequencing, and basic local alignment search tool (BLAST) analysis was then used to genetically characterize the causative organisms.Results: Three isolates were identified as Bbss that lay genotypically between strains B31 and ZS7 and were then characterized as strain 64b. One of the three isolates though may have similarity to B. bissettii a Bbsl. The fourth isolate was more appropriately placed in the sensu lato group and appeared to be similar, but not identical to, a B. valaisiana-type isolate. In this study, a central biopsy taken within 6 days of infection was used instead of conventional sampling at the leading edge, and the merits of this are discussed.Conclusion: These patients acquired infection in Australia, further proving endemic LD on the continent. Central biopsy site of EM is a useful tool for PCR evaluation. BLAST searches suggest a genetic diversity of B. burgdorferi, which has implications concerning the diagnosis, clinical severity, and testing of LD in Australia.