Przegląd badań in vitro oceniających aktywność przeciwdrobnoustrojową olejku z drzewa herbacianego ( Tea Tree Oil). Cz. I

Aleksandra Garbusińska, *Anna Mertas, Wojciech Król

Summary
Tea Tree Oil (TTO) is the natural substance obtained by steam distillation from the plant Melaleuca alternifolia. That essential oil is a complex mixture of monoterpenes, sesquiterpenes and related alcohols, consisting of approximately 100 components. The concentrations of these components are stipulated by an Australian Standard. Terpinen-4-ol (one of the putative antimicrobial components) should be at least 30% of the TTO while 1,8-cineole (reputedly a skin irritant) should be less than 15%. TTO exhibits a broad spectrum of antimicrobial activity against a wide range of Gram-positive and Gram-negative bacteria, viruses and fungi (yeasts and dermatophytes). TTO is used medicinally as a topical antiseptic in the treatment of the mucosal and cutaneous infections.
The antibacterial and antifungal effectiveness of TTO and its components were tested in vitro including clinically significant microorganisms. Most reported studies were based on using of the broth dilutions methods. In this method a serial doubling dilutions of each agent were prepared in broth, inoculated with microorganism cells suspension and incubated. Following this MIC (Minimal Inhibitory Concentration) was determined as the lowest concentration of the study substance resulting in the visual reduction of the growth of the inoculum. MBC or MFC (Minimal Bactericidal or Fungicidal Concentration) were determined as the lowest concentration of the study substance resulting in the death 99,9% or more of the inoculum. In reported agar diffusion methods the paper discs impregnated with TTO or oil component were placed on the inoculated agar surfaces. After incubation the zones of growth inhibition were determined. In another method, assessed the viability of the microorganisms with the time-kill curves determinations, antimicrobial effect of TTO or its components was evaluated by measuring the levels reduction in the numbers of CFU/ml over a specified time.
The mechanism of antimicrobial action of TTO was elucidated too. TTO treatment of microorganisms cells resulted in the loss of cell membrane integrity and its function. In the electron microscopy the bacteria cells treated with TTO and its components showed morphology changes. Inhibition of cells respiration and the leakage of K⁺ ions from bacteria in response to TTO and the rate of this efflux were monitored too.

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