Abstract
Lyme disease is a most common vector borne disease in the US. Although the majority of Lyme patients can be cured with the standard 30 day antibiotic treatment, about 10-20% of patients continue to suffer from prolonged post-treatment Lyme disease syndrome (PTLDS). While the cause for this is unclear, one possibility is that persisting organisms are not killed by current Lyme antibiotics. It has been reported in the literature that essential oils have antimicrobial activities and some have been used by patients with persisting symptoms with varying degree of improvement. However, the activity of essential oils on the causative agent Borrelia burgdorferi (B. burgdorferi) has not been studied. Here, we evaluated the activity of a panel of 34 essential oils for activity against B. burgdorferi stationary phase cells. Interestingly, we found that many essential oils had varying degrees of activity against the stationary phase B. burgdorferi. In particular, the top 5 essential oils (oregano, cinnamon bark, clove bud, citronella, and wintergreen) at a low concentration of 0.25% showed more activity than the persister drug daptomycin (40 microM). An interesting observation is that the highly active essential oils were found to have excellent anti-biofilm ability as shown by their ability to dissolve the aggregated biofilm-like structures. In subculture studies, the three top hits, oregano, cinnamon bark and clove bud completely eradicated all viable cells without any regrowth, but citronella, wintergreen, and geranium bourbon could not completely kill the stationary phase B. burgdorferi with many spirochetes being visible after 21-day subculture. In addition, carvacrol was found to be the most active ingredient of oregano oil and had excellent activity against B. burgdorferi stationary phase cells, while p-cymene and alpha-terpinene had no apparent activity. Future studies are needed to further evaluate and optimize the active essential oils and in drug combinations in vitro and in vivo for improved treatment of persistent Lyme disease.
