Good evidence shows that components of Borrelia burgdorferi can remain detectable after organisms have been killed or rendered nonviable, but the evidence is much stronger for some components than others. Importantly, detecting these materials does not by itself demonstrate persistent viable infection.
Borrelia-Derived Material That May Remain After Bacterial Death
| # | Borrelia Material | Evidence for Persistence After Killing/Treatment | Potential Biological Importance |
|---|---|---|---|
| 1 | Peptidoglycan (PG) | Strong—human evidence | Potent inflammatory antigen |
| 2 | Peptidoglycan fragments / muropeptides | Strong | NOD2 activation, cytokines |
| 3 | Cell-wall remnants | Moderate–strong | Persistent antigenic material |
| 4 | Borrelial proteins/antigens | Strong in animals | Can remain near cartilage |
| 5 | Outer-surface lipoproteins | Plausible/experimental | TLR-mediated inflammation |
| 6 | OspA | Reported post-treatment in animal tissue | Immunogenic lipoprotein |
| 7 | Other borrelial lipoprotein antigens | Animal/experimental evidence | Innate/adaptive immune activation |
| 8 | Membrane fragments | Experimental/pathologic model | Carry proteins/lipids |
| 9 | Outer-membrane vesicles/blebs | Biologically demonstrated | Can contain proteins and nucleic acids |
| 10 | Glycolipids | Established Borrelia components; persistence less certain | Immunogenic/inflammatory |
| 11 | DNA | Strong experimental evidence | PCR can remain positive after loss of viability |
| 12 | Genomic DNA fragments | Strong experimental evidence | Can produce residual PCR signal |
| 13 | Plasmid-derived DNA | Possible as part of residual DNA | Molecular debris |
| 14 | RNA | Demonstrated experimentally for a shorter period | Does not necessarily prove viability |
| 15 | mRNA | Demonstrated after killing in vitro | Shorter-lived than DNA |
| 16 | ospA transcripts | Demonstrated experimentally | Molecular remnant |
| 17 | ospC transcripts | Demonstrated experimentally | Molecular remnant |
| 18 | flaB transcripts | Demonstrated experimentally | Molecular remnant |
| 19 | pfk transcripts | Demonstrated experimentally | Molecular remnant |
| 20 | Flagellar proteins/fragments | Plausible component of spirochetal debris | Antigenic material |
| 21 | Adhesin-containing remnants | Experimental animal evidence indirectly supports ECM retention | May facilitate tissue retention |
| 22 | DbpA-associated debris | Animal evidence | Association with ECM/decorin |
| 23 | DbpB-associated debris | Animal evidence | Association with ECM/decorin |
| 24 | Whole noninfectious spirochetal remnants | Demonstrated in mice | Antigen reservoir |
| 25 | Nonmotile spirochetal structures | Animal experimental observations | Viability uncertain |
| 26 | Protein-containing vesicular debris | Experimental model | Persistent antigen delivery |
| 27 | DNA + protein-containing vesicles | Experimental/pathologic model | Molecular/antigenic debris |
| 28 | Protein-only bacterial remnants | Experimental/pathologic model | May remain after nucleic acids disappear |
| 29 | ECM-trapped borrelial debris | Animal evidence supports concept | May slow clearance |
| 30 | Cartilage-associated Borrelia antigens | Strong mouse evidence | Particularly relevant to persistent joint inflammation |
The four best-supported categories are therefore peptidoglycan/muropeptides, borrelial antigens/proteins, nucleic acids, and tissue-trapped spirochetal debris.
1. Peptidoglycan — Strongest Human Evidence
This is probably the most important answer to your question.
B. burgdorferi has an unusual peptidoglycan (PG^Bb). Unlike many bacteria, Borrelia does not efficiently recycle its peptidoglycan during growth and instead sheds substantial quantities of PG fragments.
Jutras and colleagues found Borrelia peptidoglycan in 32 of 34 (94%) synovial-fluid samples from patients with Lyme arthritis. Importantly, many of these patients had already received oral and IV antibiotics.
The authors specifically proposed two mechanisms: PG fragments produced during growth can remain behind, and additional PG can be liberated when Borrelia undergoes lysis from natural death, immune attack, or antibiotic killing.
Full reference: Jutras BL, Lochhead RB, Kloos ZA, Biboy J, Strle K, Booth CJ, Govers SK, Gray J, Schumann P, Vollmer W, Bockenstedt LK, Steere AC, Jacobs-Wagner C. Borrelia burgdorferi peptidoglycan is a persistent antigen in patients with Lyme arthritis. Proceedings of the National Academy of Sciences USA. 2019;116(27):13498-13507. doi:10.1073/pnas.1904170116.
2. Muropeptides
These are smaller molecular fragments derived from peptidoglycan.
They matter because they aren’t necessarily inert garbage. Borrelial PG fragments can stimulate the intracellular pattern-recognition receptor NOD2, resulting in inflammatory cytokine production.
This creates an important conceptual sequence:
Borrelia death/turnover → PG/muropeptide release → incomplete tissue clearance → NOD2 recognition → inflammatory signaling
That mechanism has substantially stronger evidence than a generic claim that undefined bacterial “toxins” accumulate after Lyme treatment.
Full reference: Jutras BL, Lochhead RB, Kloos ZA, et al. Borrelia burgdorferi peptidoglycan is a persistent antigen in patients with Lyme arthritis. Proc Natl Acad Sci USA. 2019;116(27):13498-13507. doi:10.1073/pnas.1904170116.
3. Borrelial Proteins and Antigens
Bockenstedt and colleagues provided particularly interesting animal evidence.
After antibiotic treatment of experimentally infected mice, they found Borrelia antigens remaining adjacent to cartilage even though infectious spirochetes were not demonstrated.
This supports a model in which bacterial killing and antigen elimination occur on very different time scales.
Full reference: Bockenstedt LK, Gonzalez DG, Haberman AM, Belperron AA. Spirochete antigens persist near cartilage after murine Lyme borreliosis therapy. Journal of Clinical Investigation. 2012;122(7):2652-2660. doi:10.1172/JCI58813.
4. DNA
Borrelia DNA can remain detectable considerably longer than viable organisms.
Iyer and colleagues exposed B. burgdorferi to ceftriaxone. Organisms could no longer be successfully subcultured by day 3, yet Borrelia DNA remained PCR-detectable for up to 56 days.
This is extremely important clinically and experimentally:
PCR-positive ≠ necessarily living Borrelia.
Residual bacterial DNA can explain at least some post-treatment PCR positivity.
Full reference: Iyer R, Mukherjee P, Wang K, Simons J, Wormser GP, Schwartz I. Detection of Borrelia burgdorferi nucleic acids after antibiotic treatment does not confirm viability. Journal of Clinical Microbiology. 2013;51(3):857-862. doi:10.1128/JCM.02785-12.
5. RNA and mRNA
RNA is generally less persistent than DNA, but it does not necessarily disappear immediately when an organism loses cultivability.
In the same experiment, transcripts from ospC, ospA, flaB and pfk remained detectable for a period following ceftriaxone exposure. Some transcripts were detectable through day 14, while all four were essentially undetectable by 28 days.
Therefore, even RNA detection must be interpreted carefully as a marker of viability.
Full reference: Iyer R, Mukherjee P, Wang K, Simons J, Wormser GP, Schwartz I. Detection of Borrelia burgdorferi nucleic acids after antibiotic treatment does not confirm viability. J Clin Microbiol. 2013;51(3):857-862. doi:10.1128/JCM.02785-12.
6. Membrane Blebs and Vesicular Material
Spirochetal destruction can generate membrane fragments and blebs containing proteins and sometimes nucleic acids.
Barbour described a useful spectrum of Borrelia remnants after antimicrobial/immune injury: increasingly damaged bacterial structures can progress to vesicular debris containing DNA and protein, then ultimately proteinaceous remnants after nucleic acids have degraded.
Full reference: Barbour AG. Remains of infection. Journal of Clinical Investigation. 2012;122(7):2344-2346. doi:10.1172/JCI63974.
7. Extracellular-Matrix–Trapped Debris
Another important concept is physical retention rather than continued bacterial replication.
A systematic review of animal experiments found evidence consistent with borrelial debris becoming retained within collagenous/extracellular-matrix tissues. Interestingly, detectable post-treatment DNA was associated experimentally with Borrelia’s decorin-binding proteins DbpA/DbpB, suggesting that attachment to extracellular matrix may contribute to retention.
Full reference: Verschoor YL, et al. Persistent Borrelia burgdorferi sensu lato infection after antibiotic treatment: systematic overview and appraisal of the current evidence from experimental animal models. Clinical Microbiology Reviews. 2023;36. doi:10.1128/cmr.00074-22.
What Could Persist the Longest?
Based on current evidence, I would rank the biologically important residual materials approximately as:
Peptidoglycan / muropeptides
↓
tissue-retained Borrelia antigens and proteinaceous debris
↓
membrane/cell-envelope fragments
↓
DNA-containing remnants
↓
free/residual RNA
But an exact human clearance half-life has not been established for most of these materials, so assigning numbers of days or months to each would be misleading.
The particularly compelling finding is peptidoglycan, because unlike a PCR signal, it has been directly demonstrated in human Lyme arthritis synovial fluid after substantial antibiotic treatment and has a plausible inflammatory mechanism through innate immune recognition.
One other important point: I would not call all of these substances “toxins.” Borrelia does not fit the classic endotoxin/exotoxin model. It is more accurate to call them persistent microbial antigens, pathogen-associated molecular patterns (PAMPs), cell-envelope fragments, nucleic-acid remnants, and spirochetal debris.