In vitro evaluation of antibacterial activity of phytochemicals and micronutrients against Borrelia burgdorferi and Borrelia garinii

Abstract

AimsLittle is known about the effects of phytochemicals against Borrelia sp. causing Lyme disease. Current therapeutic approach to this disease is limited to antibiotics. This study examined the anti‐borreliae efficacy of several plant‐derived compounds and micronutrients.Methods and ResultsWe tested the efficacy of 15 phytochemicals and micronutrients against three morphological forms of Borrelia burgdoferi and Borrelia garinii: spirochetes, latent rounded forms and biofilm. The results showed that the most potent substances against the spirochete and rounded forms of B. burgdorferi and B. garinii were cis‐2‐decenoic acid, baicalein, monolaurin and kelp (iodine); whereas, only baicalein and monolaurin revealed significant activity against the biofilm. Moreover, cis‐2‐decenoic acid, baicalein and monolaurin did not cause statistically significant cytotoxicity to human HepG2 cells up to 125 μg ml−1 and kelp up to 20 μg ml−1.ConclusionsThe most effective antimicrobial compounds against all morphological forms of the two tested Borrelia sp. were baicalein and monolaurin. This might indicate that the presence of fatty acid and phenyl groups is important for comprehensive antibacterial activity.Significance and Impact of the StudyThis study reveals the potential of phytochemicals as an important tool in the fight against the species of Borrelia causing Lyme disease.

Cooperation of Doxycycline with Phytochemicals and Micronutrients Against Active and Persistent Forms of Borrelia sp

“…These were baicalein, luteolin, monolaurin, 10-HAD, and iodine for B. burgdorferi , as well as baicalein and monolaurin for B. garinii . The other tested agents such as rosmarinic acid, vitamin D3, and vitamin C did not display such effect 47. The results obtained from this study show that neither synergy nor antagonism was observed.…”

“…Our recent study documented that other naturally occurring compounds like baicalein and luteolin, belonging to the flavones, are also potent against Borrelia sp. In addition, fatty acids, including monolaurin and cis-2-decenoic acid, and iodine exhibited significant bacteriostatic and bactericidal activities 47. Our and other studies indicate that naturally derived compounds and antibiotics that display essential anti-borreliae activities might be an option for achieving optimal bacteriostatic and bactericidal activity at lower MICs and MBCs, which could potentially reduce their side effects and treatment costs.…”

“…Our previous results indicated that among several tested compounds, a few (baicalein, luteolin, monolaurin, 10-HAD, and iodine) showed anti-rounded forms efficacy that satisfied the MBC 50 requirement. The other agents (rosmarinic acid, vitamin D3, vitamin C, and doxycycline) did not affect rounded forms to this extent 47. Evaluation of all the phytochemicals and micronutrients in combination with doxycycline did not indicate synergy or antagonistic interaction in any of the cases.…”

“…However, the exposure of Borrelia sp. to doxycycline concentration even 10-20 times higher than its MIC value did not show efficacy towards rounded forms 2, 47. That might lead to a subsequent loss of doxycycline efficacy in vitro and in vivo when applied long-term.…”

“…Briefly, 1 x 10 7 spirochetes/ml of the homogeneous culture were inoculated into four-well chambers coated with collagen type I and incubated at 33°C in 5% CO 2 for up to one week. Earlier studies in our laboratory have documented a lack of antifungal carryover using this procedure 47. Once the biofilm was established, all chambers were supplemented with the tested combinations of agents and incubated at 33°C in 5% CO 2 for up to 72 h. Control wells were treated with ethanol (0.1-0.4 v/v) alone.…”