In the master's thesis, we have analyzed the impact of fifteen herbal preparations on bacterial growth inhibition of twenty strains of Enterococcus spp. and eight strains of Lactobacillus spp.. We have observed also a stimulating effect of chosen preparations on growth of probiotic Lactobacillus strains and an impact of selected plant extract on enterococci adhesion. We have tested the ethanol extracts of leaves, fruits, seeds or flowers of Alpinia katsumadai, Calluna vulgaris, Plantago lanceolata, Humulus lupulus, Juniperus communis and Aframomum melegueta, ethanol extracts of waste material after distillation of essential oils or oil per se (J. communis). Among industrial preparations, there were also two samples with royal jelly and dihidroquercetin and also three samples with different concentrations of arabinogalactan. We found that a selection of bacteria and source of the extract has a strong influence on the minimal inhibitory concentration (MIC) of preparations. Enterococci were more resistant (MICs 1 - 4 mg/ml) compared to the lactobacilli, with lower MIC values (0.25-1 mg/ml). The best antimicrobial activity was found in hop and “Erica flos” preparations, the latter ones especially against most resistant E. faecium strains. Among preparations with stimulating activity on bacterial growth, royal jelly samples stimulated mostly L. rhamnosus and L. plantarum strains while arabinogalactane stimulated especially L. paracasei. In the last attempt we have studied antiadhesion effect of subinhibitory concentrations (1000 -6.25 mg/ml) of A. melegueta extract on selected enterococci, but we could not confirm it.
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