Antibacterial and Antioxidant Activity of Essential Oil Terpenes against Pathogenic and Spoilage-Forming Bacteria and Cell Structure-Activity Relationships Evaluated by SEM Microscopy

The antibacterial activity and antioxidant effect of the compounds α-terpineol,
linalool, eucalyptol and α-pinene obtained from essential oils (EOs), against pathogenic
and spoilage forming bacteria were determined. The antibacterial activities of these
compounds were observed in vitro on four Gram-negative and three Gram-positive strains.
S. putrefaciens was the most resistant bacteria to all tested components, with MIC values
of 2% or higher, whereas E. coli O157:H7 was the most sensitive strain among the tested
bacteria. Eucalyptol extended the lag phase of S. Typhimurium, E. coli O157:H7 and
S. aureus at the concentrations of 0.7%, 0.6% and 1%, respectively. In vitro cell growth
experiments showed the tested compounds had toxic effects on all bacterial species with
different level of potency. Synergistic and additive effects were observed at least one dose
pair of combination against S. Typhimurium, E. coli O157:H7 and S. aureus, however
antagonistic effects were not found in these combinations. The results of this first study are
encouraging for further investigations on mechanisms of antimicrobial activity of these
EO components.