Efficacy of Doxycycline in Combination with Iodine against Biofilm of Borrelia burgdorferi and Borrelia garinii

Anna Goc, Aleksandra Niedzwiecki, Matthias Rath

Presented at: 7th ASM Conference on Biofilms, October 24-29, 2015, Chicago, IL

Published in: American Society for Microbiology Final Program, pg. 43, Poster #154


Background: The ability of Borrelia sp. to convert from their spirochete form into biofilm was observed. Such “self-defense” limits the antimicrobial action of many antimicrobial agents. Thus, there is a continuous search for either new agents or enhancing efficacy of already existing ones. The goal of this study was to evaluate the action of the unorthodox combination of doxycycline (the most frequently prescribed antibiotic for Lyme patients) with iodine (one of the oldest antimicrobial agent) against biofilm of Borrelia sp. Methods: Anti-biofilm effect of doxycycline-iodine combination was assessed in 48-well chambers coated with collagen type I on biofilm of Borrelia burgdorferi (prevalent in the USA) and Borrelia garinii (prevalent in Europe) at their MIC values and three dilutions above (2-6xMIC) as well as three dilutions below (1/2-1/8xMIC), followed by staining with crystal violet and LIVE/DEAD BacLight fluorescence dye. Synergic effect was defined using fractional inhibitory concentration. Qualitative and quantitative measurements were supported by Student t-test statistical analysis. All experiments were performed in triplicates. Results: The results have shown that combination of doxycycline with iodine exhibit amended anti-biofilm effect. Synergistic effect was noticed in preventing biofilm formation. Additive reduction of mature biofilm was achieved. Although complete elimination of mature biofilm was not noted, tested combination of agents greatly reduced viable organisms in term of qualitative effect. Conclusions: Obtained data revealed that commercial antibiotic doxycycline may act with iodine and such combination has a potent anti-biofilm activity against examined Borrelia sp.