Borreliella burgdorferi Antimicrobial-Tolerant Persistence in Lyme Disease and Posttreatment Lyme Disease Syndromes

Abstract

The annual incidence of Lyme disease, caused by tick-transmitted Borreliella burgdorferi, is estimated to be at least 476,000 cases in the United States and many more worldwide. Ten to 20% of antimicrobial-treated Lyme disease patients display posttreatment Lyme disease syndrome (PTLDS), a clinical complication whose etiology and pathogenesis remain uncertain. Autoimmunity, cross-reactivity, molecular mimicry, coinfections, and borrelial tolerance to antimicrobials/persistence have been hypothesized and studied as potential causes of PTLDS. Studies of borrelial tolerance/persistence in vitro in response to antimicrobials and experimental studies in mice and nonhuman primates, taken together with clinical reports, have revealed that B. burgdorferi becomes tolerant to antimicrobials and may sometimes persist in animals and humans after the currently recommended antimicrobial treatment. Moreover, B. burgdorferi is pleomorphic and can generate viable-but-nonculturable bacteria, states also involved in antimicrobial tolerance. The multiple regulatory pathways and structural genes involved in mediating this tolerance to antimicrobials and environmental stressors by persistence might include the stringent (rel and dksA) and host adaptation (rpoS) responses, sugar metabolism (glpD), and polypeptide transporters (opp). Application of this recently reported knowledge to clinical studies can be expected to clarify the potential role of bacterial antibacterial tolerance/persistence in Lyme disease and PTLDS.

Keywords: Borrelia burgdorferi; Lyme disease; antimicrobial tolerance; bacterial persistence; persistence; post-Lyme disease syndromes; post-treatment syndromes.

FIG 1

Inflammatory infiltrates and antimicrobial-tolerant persistent B. burgdorferi in tick-inoculated rhesus macaques 8 to 9 months after treatment with oral doxycycline (5 mg/kg of body weight, twice a day for 28 days) (12 to 13 months after inoculation) (163). (A) Spinal cord and peripheral nerves. (a) Mild inflammation surrounding a cervical spinal nerve. (b) Minimal to mild mononuclear inflammation in tibial nerve. Inflammation tended to be distributed perivascularly in perineural fibrous connective tissue. (c) Section of a spirochete in the spinal cord immunostained with rabbit polyclonal B. burgdorferi-specific antibody (164). (B) Brain and meninges. (a) Mononuclear perivascular cuffing in a focal area of the brain adjacent to the fourth ventricle of the medulla. (b) Multiple spirochetes in the cerebral parenchyma immunostained with rabbit polyclonal B. burgdorferi-specific antibody (164). (C) Joints and skeletal muscle. (a) Mild synovial hyperplasia with piling up of the synovial epithelium and minimal concurrent inflammation. (b) Minimal to mild mononuclear cell infiltration in skeletal muscle interstitium. (c and d) Three-dimensional reconstruction of an immunostained section of skeletal muscle to show the cross-section of a persistent spirochete identified by dual staining with rabbit polyclonal and mouse monoclonal anti-B. burgdorferi OspA antibodies. (D) Heart. (a) Localized interstitial mononuclear cell foci adjacent to a coronary blood vessel. (b) A persistent spirochete within the myocardium identified by IFA with mouse monoclonal anti-B. burgdorferi OspA antibody. (c) Persistent B. burgdorferi spirochetes from macaque heart tissue cultured in an in vivo culture system identified by IFA with a mixture of mouse monoclonal anti-B. burgdorferi OspA and anti-B. burgdorferi OspC antibodies (164). Samples of these cultures were positive for ospA and oppA-2 transcripts identified by quantitative RT-PCR (data not shown) (163).

FIG 2

B. burgdorferi in xenodiagnostic tick midgut contents (163). (a) Antimicrobial-tolerant persistent spirochetes identified by IFA with mouse monoclonal anti-OspA antibody in ticks fed on treated rhesus macaques approximately 7 months postinoculation. (b) Viability of these spirochetes confirmed by RT-PCR for B. burgdorferi ospA and ospC. *, clear positive; ^, potential positive. M1, M2, and M3 represent cohort-matched controls derived from feeding ticks on clean mice.