Antimicrobial activity of Thymus longicaulis C. Presl essential oil against respiratory tract pathogens

Thymus longicaulis C. Presl is a small aromatic perennial herb of Lamiaceae family and a typical representative of the Illyric-Mediterranean flora. This species is a traditional remedy for cold, flu, cough, nephritis and abdominal pain [1]. Present study aimed to evaluate composition of essential oil and its in vitro antimicrobial activity against major respiratory tract pathogens which show increasing resistance to commonly prescribed antimicrobials [2]. The yield of essential oil obtained by hydrodistillation from aerial plant parts was 12ml/kg. According to the GC-MS analysis, a total of 41 compounds (99%) were identified. Thymol (46.3%), γ-terpinene (16.2%), thymyl methyl ether (11.4%), and p-cymene (9.4%) were the main components. Antimicrobial activity of the essential oil was determined using microdilution broth assay (tested concentrations were 0.2–25mg/ml). Amoxicillin-clavulanate and fluconazole were used in order to control sensitivity of tested clinically isolated bacterial and yeast strains: Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes and Candida albicans. The essential oil exhibited antimicrobial activity against all tested pathogens. The most sensitive strains were H. influenzae and S. pneumoniae (MIC 0.78mg/ml), while S. aureus was the most resistant (MIC >25mg/ml). Our results revealed that T. longicaullis from Croatia is rich in essential oil characterized by a high content of thymol. A strong antimicrobial effect of the essential oil proved in this study indicates on its huge potential in the treatment of respiratory tract infections.

References: 1. Kütür, S. (2007)J. Ethnopharmacol. 111:341–364.

2. Klugman KP. (2007) Int. J. Antimicrob. Agents 29:6–10.