Persistence of Borrelia burgdorferi in Rhesus Macaques following Antibiotic Treatment of Disseminated Infection

Abstract

The persistence of symptoms in Lyme disease patients following antibiotic therapy, and their causes, continue to be a matter of intense controversy. The studies presented here explore antibiotic efficacy using nonhuman primates. Rhesus macaques were infected with B. burgdorferi and a portion received aggressive antibiotic therapy 4–6 months later. Multiple methods were utilized for detection of residual organisms, including the feeding of lab-reared ticks on monkeys (xenodiagnosis), culture, immunofluorescence and PCR. Antibody responses to the B. burgdorferi-specific C6 diagnostic peptide were measured longitudinally and declined in all treated animals. B. burgdorferi antigen, DNA and RNA were detected in the tissues of treated animals. Finally, small numbers of intact spirochetes were recovered by xenodiagnosis from treated monkeys. These results demonstrate that B. burgdorferi can withstand antibiotic treatment, administered post-dissemination, in a primate host. Though B. burgdorferi is not known to possess resistance mechanisms and is susceptible to the standard antibiotics (doxycycline, ceftriaxone) in vitro, it appears to become tolerant post-dissemination in the primate host. This finding raises important questions about the pathogenicity of antibiotic-tolerant persisters and whether or not they can contribute to symptoms post-treatment.

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

“…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.)…”

“…It has been suggested that B. burgdorferi may be sequestered in protective niches during animal infection such that antibiotics might be less effective (11,12,41). On the other hand, it is also possible that the host's immunologic response and/or other inhibitory factors found in vivo could result in a more rapid decrease in viability after exposure to an antibiotic than occurs after the same level of antibiotic exposure during in vitro cultivation.…”

“…The question of whether there might be residual infection in treated patients has also prompted a number of studies of the efficacy of antibiotic therapy in eradicating B. burgdorferi from infected animals (10)(11)(12). These studies have had various results, and a number of methodological limitations have made the findings difficult to interpret (12,13).…”

“…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).…”

Spirochete antigens persist near cartilage after murine Lyme borreliosis therapy

“…A recent study in the primate model of Lyme borreliosis reported detection of spirochetes after antibiotic therapy, a conclusion that should be interpreted with caution (33). Subtherapeutic antibiotic levels were documented in experimental animals and measures of infection in the control sham-treated monkeys were not sufficiently robust to distinguish between inadequate treatment and the persistence of a subpopulation with antibiotic tolerance.…”