Reciprocal Cooperation of Phytochemicals against Borrelia burgdorferi and Borrelia garinii

Authors: Anna Goc, Aleksandra Niedzwiecki, Matthias Rath

Presented at: ASM Microbe 2016; June 16–20, 2016 | Boston, MA

Published in: ASM Microbe 2016 Final Program and as a press release; Poster # MONDAY-400

Background: Lyme borreliosis is a tick-borne disease caused by the spirochete Borrelia burgdorferi sensu lato. Throughout nature, phytochemicals represent a growing theme in antimicrobial defense, however, little is known about their anti-borrelaea reciprocal cooperation. To better understand this subject, we studied the efficacy of selected phytochemicals such as flavones and fatty acids to ascertain the type of their related cooperation against Borrelia sp. Methods: Phytochemicals such as baicalein, luteolin, 10-HAD, and glycerol monolaurate were tested in different “two-agent” combinations for their in vitro effectiveness against vegetative (spirochetes) and dormant (rounded bodies, biofilm) forms of Borrelia burgdorferi and Borrelia garini, using dark field and fluorescence microscope. Antibacterial effects of these agents’ cooperation were evaluated at their MIC values and three dilutions above (2-6 X MIC) as well as three dilutions below their MICs (1/2-1/8 X MIC), according to checkerboard assays, and defined by fractional inhibitory concentration index. Additionally, a Student t-test statistical analysis was performed for further validation. All experiments were performed in triplicates. Results: The results showed that the combination of baicalein with luteolin exhibited synergistic anti-spirochetal as well as additive effects against rounded forms and biofilm of both studied Borrelia sp, whereas their respective cooperation with tested fatty acids showed to be additive against spirochetes and indifferent against other morphological forms. Moreover, additive anti-spirochetal and anti-biofilm effects were observed when monolaurin was used in combination with 10-HAD. Antagonism was not observed in any of the cases. Conclusions: The data obtained from this in vitrostudy revealed the intrinsic anti-borreliaea activity of tested combinations of flavones and fatty acids, respectively. Therefore, they may represent valuable adjuvants for antimicrobial chemotherapy.

Press release by ASM Microbe 2016: