Biofilm Structures of Borrelia burgdorferi Not Only Display More Tolerance to Lyme Antibiotics But Also Cause More Severe Pathology In a Mouse Arthritis Model: Implications for Understanding Persistence, PTLDS and Treatment

Abstract

Lyme disease, caused by Borrelia burgdorferi, is the most common tick-borne illness in US and Europe. While most patients can be cured with a 2-4 week antibiotic therapy, about 10%-20% patients continue to suffer persistent symptoms of fatigue, pain or joint and muscle aches, and neurocognitive despite the treatment, a condition called post-treatment Lyme disease syndrome (PTLDS). The cause for PTLDS is unclear but one possibility is persistent infection with B. burgdorferi. B. burgdorferi is known to develop morphological variant forms such as round bodies and aggregated biofilm-like microcolonies as a log phase culture consisting of spirochete form grows into stationary phase. Here we isolated biofilm-like microcolony and planktonic form (spirochetal forms and round body) from stationary phase culture and found that the stationary phase planktonic form (SP) and microcolony form (MC) were much more tolerant to the current antibiotics for Lyme disease, doxycycline, ceftriaxone and cefuroxime than log phase spirochete form (LOG). In addition, we also compared the ability of the variant forms to cause disease in a mouse arthritis model. Surprisingly, the MC in particular and the SP caused a more severe arthritis with an earlier onset of inflammation and joint swelling than LOG. MC-infected mice showed significant joint swelling as early as 9 days post-infection, while the LOG and SP did not cause significant swelling. At 21 days, the joint swelling of the MC group dramatically increased and peaked, while the SP showed significant swelling at this time but less severe than the MC group. The LOG infected mice were just beginning to develop joint swelling at 21-day post-infection, with only slight swelling. At 30-day post infection, the SP group mice also developed similar severity of joint swelling as the MC group, but the LOG group still did not show significant swelling. However, at 35-day post infection, all three infected groups showed similar degree of significant joint swelling. Thereafter, the joint swelling of the three infected groups waxed and waned during the 90-day observation. Thus, we established a new biofilm-inocula mediated visual arthritis model that could facilitate more efficient evaluation of treatment regimens for persistent B. burgdorferi infections. Our findings provide new insight about disease pathogenesis and may have implications for understanding PTLDS and PTLDS treatment failure, due to possible biofilm inoculation during tick-bite. This biofilm/persister seeding model may be valid for different microbial infections and facilitate developing more effective treatments of persistent infections in general.