bacterial resistant stages ͉ doxycycline ͉ medical symbiotics ͉ multiple sclerosis ͉ spirochete cysts

The purpose of this study was to evaluate the behaviour of Borrelia burgdorferi 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 cultivated 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 developed into regular, mobile spirochetes after 6 weeks, and their regeneration time was normal. Examination of these cysts in the transmission electron microscope revealed transverse fission inside the cysts. It is probable that similar phenomena may occur in vivo under conditions unfavourable for spirochetes. These observations may help to explain why diagnosis and treatment of B. burgdorferi infections in humans can be difficult.

The purpose of this study was to examine the structural alterations of Borrelia burgdorferi when exposed to spinal fluid. Normal, mobile spirochetes were inoculated into spinal fluid, and the spirochetes were converted to cysts (spheroplast L-forms) after 1-24 h. When these cystic forms were transferred to a rich BSK-H medium, the cysts were converted back to normal, mobile spirochetes after incubation for 9 to 17 days. The cultures were examined by dark field microscopy (DFM), interference contrast microscopy (ICM) and transmission electron microscopy (TEM). When neuroborreliosis is suspected, it is necessary to realize that B. burgdorferi can be present in a cystic form, and these cysts have to be recognized by microscopy. This study may also explain why cultivation of spinal fluid often is negative with respect to B. burgdorferi.

In this work the susceptibility of mobile and cystic forms of Borrelia burgdorferi to hydroxychloroquine (HCQ) was studied. The minimal bactericidal concentration (MBC) of HCQ against the mobile spirochetes was > 32 microg/ml at 37 degrees C, and > 128 microg/ml at 30 degrees C. Incubation with HCQ significantly reduced the conversion of mobile spirochetes to cystic forms. When incubated at 37 degrees C, the MBC for young biologically active cysts (1-day old) was > 8 microg/ml, but it was > 32 microg/ml for old cysts (1-week old). Acridine orange staining, dark-field microscopy and transmission electron microscopy revealed that the contents of the cysts were partly degraded when the concentration of HCQ was > or = MBC. At high concentrations of HCQ (256 microg/ml) about 95% of the cysts were ruptured. When the concentration of HCQ was > or = MBC, core structures did not develop inside the cysts, and the amount of RNA in these cysts decreased significantly. Spirochetal structures inside the cysts dissolved in the presence of high concentrations of HCQ. When the concentration of HCQ was > or = MBC, the core structures inside the cysts were eliminated. These observations may be valuable in the treatment of resistant infections caused by B. burgdorferi, and suggest that a combination of HCQ and a macrolide antibiotic could eradicate both cystic and mobile forms of B. burgdorferi.

Brorson 0 , Brorson SH. A rapid method for generating cystic forms of Borrelia burgdorferi, and their reversal to mobile spirochetes. APMIS 106: 1131-1141, 1998. Mobile Borrelia burgdorferi were transferred to distilled water (lo6 per ml). The cultures were observed by dark field microscopy (DFM), interference contrast microscopy (ICM) and transmission electron microscopy (TEM). 95% of the spirochetes were converted to cysts after 1 min, and after 4 h no normal mobile borreliae were observed. When transferred to growth medium (BSK-H), the cysts became smaller and more irregular, and were filled with organic substances. After 1 day, 1-5 thin structures sprouted from the cysts. They continued to grow in both length and thickness until they attained a normal spirochetal structure. Finally, these new-born spirochetes detached from the cysts, by which time their mobility had become normal. The present method for producing large amounts of cystic forms of B. burgdorferi is well suited for further studies of this unique microbe.