Ineffectiveness of Tigecycline against Persistent Borrelia burgdorferi

Abstract

The effectiveness of a new first-in-class antibiotic, tigecycline (glycylcycline), was evaluated during the early dissemination (1 week), early immune (3 weeks), or late persistent (4 months) phases of Borrelia burgdorferi infection in C3H mice. Mice were treated with high or low doses of tigecycline, saline (negative-effect controls), or a previously published regimen of ceftriaxone (positive-effect controls). Infection status was assessed at 3 months after treatment by culture, quantitative ospA real-time PCR, and subcutaneous transplantation of joint and heart tissue into SCID mice. Tissues from all saline-treated mice were culture and ospA PCR positive, tissues from all antibiotic-treated mice were culture negative, and some of the tissues from most of the mice treated with antibiotics were ospA PCR positive, although the DNA marker load was markedly decreased compared to that in saline-treated mice. Antibiotic treatment during the early stage of infection appeared to be more effective than treatment that began during later stages of infection. The viability of noncultivable spirochetes in antibiotic-treated mice (demonstrable by PCR) was confirmed by transplantation of tissue allografts from treated mice into SCID mice, with dissemination of spirochetal DNA to multiple recipient tissues, and by xenodiagnosis, including acquisition by ticks, transmission by ticks to SCID mice, and survival through molting into nymphs and then into adults. Furthermore, PCR-positive heart base tissue from antibiotic-treated mice revealed RNA transcription of several B. burgdorferi genes. These results extended previous studies with ceftriaxone, indicating that antibiotic treatment is unable to clear persisting spirochetes, which remain viable and infectious, but are nondividing or slowly dividing.

Detection of Borrelia burgdorferi Nucleic Acids after Antibiotic Treatment Does Not Confirm Viability

“…Some have relied on cultivability of the spirochete as the sole measure of antibiotic efficacy, as is conventionally employed for other microorganisms (32,38,39), whereas others have required complete elimination of all spirochetal nucleic acids and proteins (11,14,22,28,40,41). Our study and those of others suggest that the antimicrobial activity of ceftriaxone can be reliably assessed based on cultivability and that cultivation is a more accurate reflection of cell viability.…”

“…These studies have had various results, and a number of methodological limitations have made the findings difficult to interpret (12,13). Some of these investigations have concluded that viable B. burgdorferi persists in treated animals but in a dormant, noncultivable state (11,14). Analogies have been made with the well-established phenomenon of persistence of small subpopulations in studies of other bacteria when exposed to cidal antibiotics in vitro (15,16).…”

“…daily is prescribed to treat Lyme disease. We did not determine the MIC of the borrelial strains utilized in this study to ceftriaxone, but in other studies with the same strains the MIC values ranged from 0.025 to 12 g/ml (14,(30)(31)(32).…”

“…such as by losing key genetic elements, "encysting," or changing morphology to round bodies (11,14,28,29). We used a ceftriaxone concentration of 15 g/ml to replicate the minimum drug level achieved in serum when the standard dose of 2 g intravenously (i.v.)…”

Remains of infection

“…I think that the nosology of post-Lyme disease syndrome has utility and that investigations along the lines of the work described here will yield further insights not just about Lyme disease but about other postinfection sequelae, including reactive arthritis, some forms of chronic fatigue syndrome, and perhaps other disorders yet to be recSchwartz critiqued parts of the experimental designs and the interpretation of the results in these two reports (15). In a subsequent article, Barthold et al rebutted these criticisms and reported additional evidence that "noncultivable" spirochetes in the blood and tissues of treated mice were infectious on the basis of transplantation of tissue allografts and their transmission to naive mice via vector ticks (16). More recently, a paper by Embers et al added more fuel to the fire by concluding on the basis of xenodiagnosis that "B.…”