Stationary phase persister/biofilm microcolony of Borrelia burgdorferi causes more severe disease in a mouse model of Lyme arthritis: implications for understanding persistence, Post-treatment Lyme Disease Syndrome (PTLDS), and treatment failure.

Although most patients with Lyme disease can be cured with a 2-4 week antibiotic therapy, about 10-20% of patients continue to suffer prolonged persistent symptoms, a condition called post-treatment Lyme disease syndrome (PTLDS). The cause for PTLDS is unclear and hotly debated. Borrelia burgdorferi develops morphological variants under stress conditions but their significance is not clear. Here we isolated the biofilm-like microcolony (MC) and planktonic (spirochetal form and round body) (SP) variant forms from the stationary phase culture of B. burgdorferi and showed that the MC and SP variant forms were not only more tolerant to the current Lyme antibiotics but also caused more severe arthritis in mice than the log phase spirochete form (LOG). We propose to divide the persistent Lyme disease into two categories: (1) early development of persistent disease from inoculation with persister/biofilm at the beginning of infection introduced by tick bites, or Type I persistent disease (i.e., PTLDS); and (2) late development of persistent disease due to initial infection not being diagnosed or treated in time such that the infection develops into late persistent disease, or Type II persistent disease. Importantly, we show that the murine infection caused by LOG could be eradicated by ceftriaxone whereas the persistent infection established with MC could not be eradicated by doxycycline (Doxy), ceftriaxone (CefT), or vancomycin (Van), or Doxy+CefT or Van+CefT, but could only be eradicated by the persister drug combination daptomycin+doxycycline+ceftriaxone. We conclude that varying levels of persistence and pathologies of Borrelia infection and the corresponding different treatment responses are mostly dictated by the heterogeneous B. burgdorferi variant forms inoculated at the time of tick bites. These findings may have broad implications for understanding pathogenesis and treatment of not only persistent Lyme disease but also other persistent infections in general and call for studies to evaluate if treatment of persistent infections with persister drug combination regimens is more effective than the current mostly single-antibiotic monotherapy.