DISTRIBUTION AND MOLECULAR ANALYSIS OF LYME-DISEASE SPIROCHETES, BORRELIA-BURGDORFERI, ISOLATED FROM TICKS THROUGHOUT CALIFORNIA

Previous studies describing the occurrence and molecular characteristi cs of Lyme disease spirochetes, Borrelia burgdorferi, from California have been restricted primarily to isolates obtained from the north coa stal region of this large and ecologically diverse state. Our objectiv e was to look for and examine B. burgdorferi organisms isolated from I xodes pacificus ticks collected from numerous regions spanning most pa rts of California where this tick is found. Thirty-one isolates of B. burgdorferi were examined from individual or pooled I. pacificus ticks collected from 25 counties throughout the state. One isolate was obta ined from ticks collected at Wawona Campground in Yosemite National Pa rk, documenting the occurrence of the Lyme disease spirochete in an ar ea of intensive human recreational use. One isolate from an Ixodes neo tomae tick from an additional county was also examined. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblot analysis, agar ose gel electrophoresis, Southern blot analysis, and the polymerase ch ain reaction were used to examine the molecular and genetic determinan ts of these uncloned, low-passage-number isolates. All of the isolates were identified as B. burgdorferi by their protein profiles and react ivities with monoclonal and polyclonal antibodies, and all the isolate s were typed by the polymerase chain reaction as North American-type s pirochetes (B. burgdorferi sensu stricto). Although products of the os pAB locus were identified in protein analyses in all of the isolates, several isolates contained deleted forms of this locus that would resu lt in the expression of chimeric OspA-OspB proteins. The analysis of O spC demonstrated that this protein was widely conserved among the isol ates but was also quite variable in its molecular mass and the amount of it that was expressed.