Thyme belongs to a genus encompassing over 215 species of hardy perennial herbaceous plants and sub-shrubs, which are native to Europe, particularly around the Mediterranean. Thymus vulgaris L., or garden thyme, with narrow small leaves and clusters of tubular mauve flowers, is used mainly in cookery. Dried herb yields 1% and more essential oil, which is a pale yellowish-red liquid with a sweet, very aromatic odour. Thyme is widely used in the pharmaceutical industry and is a source of substances of antimicrobial effect upon antibiotic-resistant strains of microorganisms. The purpose of our work was to identify the biochemical and antimicrobial peculiarities of Th. vulgaris essential oil against clinical isolates of opportunistic microorganisms. The analysis of thyme essential oil was carried out using GC/MS analysis. The clinical isolates were isolated with the use of differentially diagnostic nutrient media. The antibiotic susceptibility was identified with the help of the disc-diffusion test. The sensitivity of microorganisms to plant extracts was determined by the agar diffusion test. The antibiofilm activity of the extracts was tested in standard 96-well microtitration plates. The GC/MS results confirm the earlier reports that the major volatile constituents obtained from the aerial parts of thyme species were thymol, γ-terpinene, p-cymene, 3-carene and carvacrol. After subjecting the selected essential oil to effective steam distillation, substantial contents of phenolic monoterpenoids were obtained – thymol (67.7%) and γ-terpinene (8.2%). The European Pharmacopoeia set quality standards for thyme essential oil, which dealt mainly with the % content (w/w) of the volatile phenols (expressed as thymol: 36.0–55.0%). Garden thyme essential oil has been found to show a high antimicrobial activity against antibiotic-resistant microorganism strains. The obtained results proved the wide spectrum of antibiotic activity of thyme essential oil. The highest antimicrobial activity was registered against the typical and clinic strains of S. aureus and microscopic Candida genus fungi. Garden thyme essential oil was ascertained to show high antibiofilm-forming activity against S. aureus. The antimicrobial and antibiofilm-forming activities of thyme essential oil against both bacterial pathogens of opportunistic infections and microscopic fungi have proven the good prospects for development of a broad-spectrum agent against opportunistic microbial associations based on this oil.

Biol. Stud. 2020: 14(1); 51–62 • DOI: https://doi.org/10.30970/sbi.1401.613 DOMINANT MICROBIAL ASSOCIATIONS OF ORAL CAVITY AT PERIODONTITIS AND FEATURES OF THEIR SENSITIVITY TO ANTIBACTERIAL DRUGS

The significant spread of antibiotic-resistant microorganisms which are part of microbial associations of the oral cavity is considered one of the main causes for the complications and relapses of inflammatory diseases of the periodontium. This problem underlines the importance of constant monitoring of the circulation of polyantibiotic-resistant isolates, and development of new approaches and means of correction for the microbiocoenosis of the oral cavity affected by inflammatory processes. The paper is dedicated to research of antimicrobial properties of essential oil compositions against opportunistic pathogenic microorganisms, agents of inflammatory diseases of the periodontium. Out of the microorganisms isolated from the nidus of inflammation, the extra antibiotic-resistant ones were chosen. For the purpose of antibiotic susceptibility and antimicrobial activity testing, the disc diffusion method was used. The following compositions were manufactured from essential oils: Hyssopus officinalis L. + Rossmarinus officinalis L.; Menta piperita L. + H. officinalis; R. officinalis + Coriandrum sativum L.; R. officinalis + M. piperita + H. officinalis. The compositions H. officinalis + R. officinalis; M. piperita + H. officinalis were shown to have the highest level of antibacterial activity against clinical and typical isolates. Combinations of essential oils demonstrated a broader spectrum of activity against microorganisms than their components taken separately. Certain essential oils and the compositions H. officinalis + R. officinalis; M. piperita + H. officinalis were ascertained to have a high anti-mycotic activity against Candida genus microscopic fungi. This fact proves the advantage of application of combinations of essential oils compared to the use of their separate components. However, not all variants reviewed showed additive antimicrobial effect of the use of combinations of essential oils. The compositions that showed high antibacterial properties against the reviewed isolates may be used for oral hygiene products.