Efficacy of lavender essential oil against respiratory tract bacteria is influenced by harvesting time

Antibiotic resistance is largely associated with the biofilm-forming properties of bacteria. Respiratory pathogens are frequently arranged in a biofilm on the mucous membrane. This study investigated the composition and microbiological activity of Lavandula angustifolia Mill. essential oil (LEO) distilled from the flowers collected before, during, and after the flowering period. Our results confirmed that collection time was a significant parameter for composition and microbiological activity. The most active sample was LEO distilled before the flowering period. The most resistant pathogen was P. aeruginosa (MIC: 2.5 mg/mL), whereas the most sensitive was S. pneumoniae (MIC: 0.5 mg/mL). In the biofilm experiment, LEO during the pre-bloom period was the most effective. Its anti-biofilm activity decreased with increasing incubation time (4, 6, 8, 12, and 24 h). We proved the effectiveness of LEOs against respiratory pathogens in biofilms of different maturity; LEO distilled before flowering was the most effective.