title: Linear and circular plasmid content in Borrelia burgdorferi clinical isolates.
abstract: The genome of Borrelia burgdorferi, the etiologic agent of Lyme disease, is composed of a linear chromosome and more than 20 linear and circular plasmids. Typically, plasmid content analysis has been carried out by pulsed-field gel electrophoresis and confirmed by Southern hybridization. However, multiple plasmids of virtually identical sizes (e.g., lp28 and cp32) complicate the interpretation of such data. The present study was undertaken to investigate the complete plasmid complements of B. burgdorferi clinical isolates cultivated from patients from a single region where early Lyme disease is endemic. A total of 21 isolates obtained from the skin biopsy or blood samples of Lyme disease patients were examined for their complete plasmid complements by Southern hybridization and plasmid-specific PCR analysis. All clinical isolates harbored at least six of the nine previously characterized cp32s. Fourteen isolates harbored all B31-like linear plasmids, and seven isolates simultaneously lacked lp56, lp38, and some segments of lp28-1. The distinctive plasmid profile observed in these seven isolates was specific to organisms that had ribosomal spacer type 2 and pulsed-field gel type A, which implies a clonal origin for this genotype. The presence of nearly identical complements of multiple linear and circular plasmids in all of the human isolates suggests that these plasmids may be particularly necessary for infection, adaptation, and/or maintenance in the infected host.
authors.affiliation: Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595, USA.
authors.forename: Radha
authors.initials: R
authors.lastname: Iyer
authors.forename: Ogori
authors.initials: O
authors.lastname: Kalu
authors.forename: Joye
authors.initials: J
authors.lastname: Purser
authors.forename: Steven
authors.initials: S
authors.lastname: Norris
authors.forename: Brian
authors.initials: B
authors.lastname: Stevenson
authors.forename: Ira
authors.initials: I
authors.lastname: Schwartz
mesh_terms: D016470:Bacteremia / Q000382:microbiology; D025065:Borrelia burgdorferi / Q000235:genetics* / Q000472:pathogenicity; D006801:Humans; D010957:Plasmids; D012867:Skin / Q000382:microbiology