TRANSFORMATION OF CYSTIC FORMS OF BORRELIA-BURGDORFERI TO NORMAL, MOBILE SPIROCHETES

The purpose of this study was to evaluate the behaviour of Borrelia bu rgdorferi under controlled conditions. The occurrence of cystic forms of Borrelia burgdorferi in vitro was noted, and these cysts were able to be transformed to normal, mobile spirochetes. B. burgdorferi was cu ltivated in a commercial culture medium without serum, The spirochetes multiplied only slowly in this medium, and transformation to encysted forms was observed after 1 week. When these cysts were transferred to the same culture medium with rabbit serum, the encysted forms develop ed into regular, mobile spirochetes after 6 weeks, and their regenerat ion time was normal. Examination of these cysts in the transmission el ectron microscope revealed transverse fission inside the cysts. It is probable that similar phenomena may occur in vivo under conditions unf avourable for spirochetes. These observations may help to explain why diagnosis and treatment of B. burgdorferi infections in humans can be difficult.