Activity of Essential Oils Against Bacillus subtilis Spores

Abstract

Alternative methods for controlling bacterial endospore contamination are desired in a range of industries and applications. Attention has recently turned to natural products, such as essential oils, which have sporicidal activity. In this study, a selection of essential oils was investigated to identify those with activity against Bacillus subtilis spores. Spores were exposed to 13 essential oils, and surviving spores were enumerated. Cardamom, tea tree, and juniper leaf oils were the most effective, reducing the number of viable spores by 3 logs at concentrations above 1%. Sporicidal activity was enhanced at high temperatures (60 o C) or longer exposure times (up to 1 week). Gas chromatography-mass spectrometry analysis identified the components of the active essential oils. However, none of the major oil components exhibited equivalent activity to the whole oils. The fact that oil components, either alone or in combination, did not show the same level of sporicidal activity as the complete oils suggested that minor components may be involved, or that these act synergistically with major components. Scanning electron microscopy was used to examine spores after exposure to essential oils and suggested that leakage of spore contents was the likely mode of sporicidal action. Our data have shown that essential oils exert sporicidal activity and may be useful in applications where bacterial spore reduction is desired.

The in situ bacterial production of fluorescent organic matter; an investigation at a species level

“…Physical lysis was undertaken to ensure no extra chemicals were added to the cells that may alter the fluorescence properties of the sample (nine independent replicates). An endospore suspension for B. subtilis was prepared as described by Lawrence and Palombo (2009). To check for the presence of endospores and the removal of vegetative cells, an endospore stain was conducted using the Schaeffer-Fulton method (Schaeffer and Fulton, 1933).…”

A review on recent research results (2008–2010) on essential oils as antimicrobials and antifungals. A review.

“…[141] Various studies show that the extent of antimicrobial activity and the mode of action are dependent on the additive and synergistic or even antagonistic effects of the individual constituents. [138,142,143] The most abundant substances in the EO of T. vulgaris were carvacrol, linalool and thymol. Additive antimicrobial activity as well as a partial synergistic effect against K. pneumoniae were noticed when the isolated monosubstances linalool and carvacrol were used in combination or linalool with thymol.…”

“…This indicated the potential existence of synergistic interactions among the individual constituents and the importance of substances which were represented in lower levels. [138] Despite of the fact that M. alternifolia EO exerts strong inhibitory activity against microbes, some bacteria are nevertheless capable of developing protection measures against it. A study proved that some P. aeruginosa strains obtain special pumps (MexAB-OprM pumps) which induce resistance towards monoterpenes which occur in M. alternifolia EO such as terpinen-4-ol, a-terpineol and 1,8-cineole by ejecting them.…”

“…[105] Beside exerting bacteriostatic and bactericidal effects EOs are also capable of impairing the development of capsules [137] and spores. [138] Cuminum cyminum L. (Apiaceae) is, on the one hand, a popular spice and, on the other hand, it is traditionally applied for its astringent and carminative effects. The EO of this plant was investigated presenting a high content of a-pinene (29.1%), limonene (21.5%) and 1,8-cineole (17.9%).…”

The Antimicrobial Properties of Cedar Leaf (Thuja plicata) Oil; A Safe and Efficient Decontamination Agent for Buildings

“…Many essential oils also possess antimicrobial properties [13,14,15,16], including oil derived from European species of Thuja [17], although many of them would not be considered safe or economical for a large scale operation. However, the oil of Western red cedar leaves ( Thuja plicata ) has been used traditionally among Aboriginal peoples of the Pacific north west to treat a variety of upper respiratory symptoms and wounds.…”